Aluminum and Copper Wire

by Marty Weiser

Introduction

This is a related article to the excellent article by Marty Weiser on Annealing Copper Wire.
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A couple of questions came up (on the IBC) regarding copper (Cu) and aluminum (Al) wire that were sent my direction. So here are both the short and the long answers after discussing with a couple of folks at work.

The Short Answer

Properly annealed copper wire can become harder during storage due to precipitation hardening. This effect will increase with increasing temperature - i.e. in the sun versus a cool spot. Aluminum wire that is too hard can be softened by annealing since it will remove the effects of work and precipitation hardening, although it is not that common for bonsai wire. In addition, the aluminum must normally be cooled rapidly after annealing to maintain the soft state.

The Long Answer

There are three major ways to harden a metal or alloy.

• The first is to work harden it by deforming the metal. This is what makes copper wire become stiffer when you apply it to the branch and is why you can break a paperclip by bending it back and forth.
• The second is precipitation hardening where you heat the alloy to allow the different elements to internally react and form a second reinforcing phase in the material. This is used for many aluminum alloys and was discovered when some parts were left in the attic of a barn over the summer.
• The third is quenching which involves heating selected alloys and then cooling them to lock in an unstable crystal structure which is generally very hard. This is used for steel cutting tools. In all three cases it is common to have some effects from the other methods going on.

I have used a some terms above (and others that will be used) that should be defined:

• Alloy - a mixture of two or more different atoms. Generally applied to metals, but can be applied to ceramics and polymers as well. Normally the alloying is intentional to improve the properties (steel is iron with carbon and other metals), but it can be due to impurities as well.
• Crystal structure - an orderly arrangement of the atoms.
• Phase - region of the same crystal structure and chemical composition.
• Dislocation - a type of disruption that allows different parts of the crystal to move relative to each other. It is like a bump in a rug that can be pushed across the room to move the rug without having to move the entire rug at once.
• Hardening - the process of making that alloy stronger. It is generally accompanied by an increase in the resistance to penetration which is what we generally call hardness.

Work Hardening in Copper

Copper and its alloys are generally hardened by work hardening since this induces dislocations to form. There are several different directions in the copper crystal for the dislocations to move just like you can start two or more bumps in a rug. However, in copper the dislocations moving in different directions have a great deal of difficulty moving around each other - they become tangled just like a case of gridlock when the traffic lights go out at rush hour. As a result, the dislocations are no longer free to move when you bend the wire so the wire is harder and stiffer. This also occurs in other metals but to different degrees. The dislocations in aluminum can move past each other fairly easily so it does not work harden a great deal. The dislocations in the steel paperclip lock up so badly that they convert into micro-cracks that eventually link up and cause the clip to break.
Wire is generally made by pulling a rod through progressively smaller dies until it reaches the correct diameter. This work hardens the alloy and can make it too hard and stiff to use. Most wire is annealed after drawing to soften it and make it more usable. Annealing is done at a temperature of around 70 - 80% of the melting temperature on a scale that starts at absolute zero (-273.15 degrees Celsius or 0 Kelvin). Annealing allows the atoms to rearrange themselves into a lower energy state. For a work hardened material the dislocations can sort themselves out and even disappear as new, much more perfect crystals arise. Copper work hardens so much that it is normally annealed one or more times between drawing steps. For electrical wire it is generally drawn to final size after the last annealing - this gives a smooth, shiny surface and a wire that has some stiffness, but not too much.

Precipitation Hardening in Aluminum

Aluminum alloys are normally hardened by precipitation hardening. The part is annealed and quenched (cooled rapidly) so that all of the different elements are mixed together on an atomic scale - this process is known as solution heat treating. This mixing is just like heating water to allow you to dissolve more sugar in the syrup. At low temperature the lowest energy state is composed of multiple phases where the different elements form different crystal structures with different chemical compositions. This process occurs very slowly at room temperature in aluminum, but heating to 100 - 200 degrees C will allow it to occur in minutes to hours and is called tempering. Copper, silicon, and magnesium are common alloying elements in aluminum and they form compounds like Al2Cu that precipitate from the matrix. These precipitates act like stop signs to the dislocations - they have to stop, but can move around the precipitate under the right conditions. As a result the alloy will become stronger since dislocation motion is slowed. Different combinations of time and temperature will result in different precipitation distributions - high temperature favors a few large ones that the dislocations cannot move around (but rarely encounter) while lower temperatures give many smaller precipitates that the dislocations that are more like yield signs, but are everywhere.

Quenching Steel

Steel (an alloy of iron (Fe) and a small amount of carbon that often has other elements added to improve the properties) is normally hardened by quenching from high temperature. Iron has a face centered cubic (FCC) crystal structure at room temperature and a body centered cubic (BCC) crystal at high temperature. Carbon dissolves better in the BCC structure and it takes time to rearrange the atoms from the FCC to the BCC and vice-versa. Quenching high temperature BCC structure from red hot (700 - 900C) to room temperature in water or a similar fluid freezes in the BCC structure. However, at room temperature the iron has shrunk a little and the carbon no longer fits so the crystal structure distorts to form a body centered tetragonal (BCT) structure. It is very, very difficult to move dislocations in the BCT structure so the steel is now very hard and brittle. Tempering the steel at a moderate temperature (300C or so) allows the iron and carbon to find a more stable structure composed of FCC iron and fine precipitates of Fe3C (a ceramic). This structure is still very hard, but will bend a little and makes a fine cutting tool.

Effect of Purity on Copper Wire

Back to our copper and aluminum bonsai wire. Bonsai consumes a very, very small amount of copper and aluminum wire compared to electrical uses so the bonsai wire makers buy electrical wire and convert it to bonsai wire. The electrical conductivity of a metal is best when the metal is fairly pure - an alloy almost always has a lower conductivity. However, higher purity is more expensive, particularly as you go beyond 99.99% purity (100 ppm impurities) so a compromise is used. Copper is fairly strong so most electrical wire is commercially pure 99.95% or better to get high conductivity. Aluminum is not as strong so the wire is normally alloyed a little copper and tempered to increase the strength so that the wire does not stretch and sag under its own weight.
The copper wire is fairly pure and the melting temperature is fairly high (1083C) so any precipitation hardening processes will be slow at room temperature. Since bonsai wire is normally annealed under less than ideal conditions (there is normally a fair bit of oxide on the surface) we can be assured that there is oxygen dissolved into the copper during annealing. A commercially important grade of copper is oxygen Free Hard Copper (OFHC) which recognizes how easily oxygen dissolves into copper. It is probably copper oxide that precipitates and makes the wire harder after a year or two. Reannealing the wire will dissolve the precipitates and make the wire softer, but unless the atmosphere is closely controlled it will probably dissolve even more oxygen into the copper so it will precipitation harden even faster.

Annealing Aluminum Wire

Aluminum and its alloys melt at a much lower temperature (450 - 560C) so precipitation hardening can occur at room temperature and temperatures that are only a little bit above room temperature. It is entirely possible that commercial aluminum wire has seen high enough temperature to become a fair bit harder, so annealing may be desireable. However, reannealing is tricky and will destroy the anodization (an organic dye in a porous aluminum oxide film). Aluminum wire should be annealed at about 300 - 350C (570 - 660F and well below red hot) for 10 -20 minutes and quenched in water. Getting the wire too hot will result in a molten mass of aluminum which is apt to react strongly with a wide variety of materials - possibly resulting in a fire that will be very, very difficult to put out. There are few such dangers with copper since the reaction with oxygen gives off far less heat and copper is a bit hard to melt with the heat sources available to most of us.

And finally

For more information on annealing copper, see Marty's companion article:

Growing Bonsai Indoors

by Brent Walston

Introduction

One of the most common misconceptions about bonsai is that they should be grown indoors. With the exception of tropicals and sub tropicals, all bonsai should be grown outdoors. Temperate climate woody plants must go through a period of cold dormancy in order to survive. This dormancy completes a yearly cycle. In deciduous trees this is a very obvious phenomenon, however, temperate evergreens such as Juniper also need to go through this cycle.
Tropicals and similar 'houseplants' can be successfully trained for bonsai and grown indoors year round. In mild climates, temperate bonsai should remain outdoors year round. In cold climates, temperate climate plants should be grown outdoors during the warm seasons of the year, but will need winter protection (the subject of another article). It is possible to grow temperate climate plants indoors in winter if they are first given the required period of dormancy.
The urge is strong for beginners to grow their bonsai indoors. Although a few traditional species for bonsai may be grown indoors year round if they are given a dormant rest period, you should be aware that this requires some skills usually obtained from growing bonsai for a few years. Below are some procedures that should be followed for indoor bonsai.

The Need for Strong Light

The major problems in indoor growing are the lack of intense light and a cool dormant period for temperate climate plants. Even if you kept your plant in an unobstructed south facing window, I doubt that the light would be sufficient for many species of woody plants. Most people just don't understand how dark it is in the house, even in front of a window.
Consider that, outside, the light comes from not only the direct sun, but from 180 degrees of sky PLUS all the reflected light of objects in the other 180 degrees. Light from a window is little better than a point source of light. If you measure the light level with your camera (not pointing it directly at the sun, but obliquely to get an average reading) you will find that the level inside is two to three f-stops lower than just outside the window. One f-stop would be half as much light, two f-stops is 1/4 as much light, etc.
From experience I can tell you that most woody plants will perform best at full sun to 50% full sun. I get 50% by growing plants under shade cloth. Less than this amount, performance falls off, and at 70% shade, plants get leggy and problems can begin.
You can correct this by putting your bonsai in the sunniest window of your dwelling, but not too close to the glass or it will experience excessive heat buildup. This light may be too intense for some tropicals that are used to growing on the forest floor, but for most woody temperate climate plants it is still insufficient. Couple this with an overhead fluorescent lamp for these species. Keep the lamp about six inches above the plant. Twin forty watt fixtures are inexpensive to purchase and use. Special bulbs are not necessary. Keep the lamp on 12 hours a day to augment the sunlight. If you lack a window with sufficient light for even low light tropicals, you can safely use fluorescent lamps as outlined above as the only source of light.

Providing a Dormant Period

The other major problem is the lack of a cool dormant period. Temperate climate plants, even evergreens, need a dormant or rest period that is activated by cooler temperatures. For most plants, this is a period of at least six to eight weeks at temperatures of 30F to 40F or lower. Most temperate woody bonsai can tolerate temperatures down to 20F without any protection. Many plants will of course lose their leaves at this time. Other species such as Chinese Elm, Ulmus parvifoliamay or may not lose their leaves during this dormant period. At mild temperatures (above freezing) they will remain evergreen, losing all of their leaves during the following season, but not all at once, so it appears evergreen. Kept outside in zone eight or less they will nearly always be deciduous (depending on the cultivar and severity of the winter). Temperate evergreen species also need a cold dormant period, but will not lose their foliage.
Without this dormant period, deciduous species will continue to grow for as much as two years, then go dormant no matter what the season or temperature. This can be very stressful for the plant, and it in some cases fatal.

Watering

Another problem is watering. Virtually no one with extensive experience in bonsai recommends watering by immersion, or watering to a schedule. This is a marketing scheme to make raising bonsai seem easy. Watering by immersion occasionally is fine, for instance if the plant is extremely dry and needs immediate resuscitation, or if it has just been repotted, or if you want to soak it in fertilizer solution. Watering by immersion tends to accumulate salts in the soil. Watering from overhead will help flush salts and waste gases from the soil. Water overhead from a watering can with a fine rose head, 'throwing' the water at the plant and waiting a few seconds for it to absorb the water, before giving it another toss. Do this until water pours from the drain holes. This will reduce runoff and keep from eroding the soil. For a single plant this might take thirty seconds. Never let a plant sit its own drain water (the rare exceptions are Wisteria and Bald Cypress growing outdoors).
Outdoor watering in sunny summer weather is easy, the plants dry out every day, so you water them everyday. Indoors is more difficult. You should only water when the plants need water, not to schedule. The interval will vary with the light level, temperature, degree of colonization of the roots in the pot, amount of foliage, and the humidity.
There are three basic methods to determine if the plant needs water. My favorite, not necessarily the best, is to simply pick the plant up. Dry plants are significantly lighter than well watered ones. You can easily learn the difference. The second is to scratch the soil with your finger and see how dry it is under the surface. It varies somewhat with soils and volume, but if the soil is dry down past a quarter of an inch, it probably needs watering. If the surface is still moist, it most definitely does not need watering. The third method is the infamous Persiano Pick, a method devised by one our illustrious Internet Bonsai Club (IBC) members. Use a piece of chopstick or wooden skewer as a sort of dipstick. Leave it in planted in the pot. To test for water pull it out and check the moisture on the stick. If the stick is dry or dryish, it's time to water. All of these methods take a little practice, but you should be able to satisfactorily learn one or all of them in about a week.

Fertilizing

You can fertilize to a schedule, and that is probably the best way. Most soluble fertilizers recommend that you fertilize full strength every other week. Simply water it in. Always use them as directed. Forget the half strength stuff for bonsai, this is a myth, use them as directed. Begin to fertilize when the plants start actively growing and stop at the beginning of the dormant period. For tropicals continue to fertilize as long as new growth is evident.

Air Circulation and Humidity

Secondary considerations, but important ones, for indoor growing are air circulation, humidity, and insect/disease control.
Air circulation in summer can be as easy as leaving the window open to get a little breeze. In winter you might want to get a very small fan to gently waft the air about your plant.
Humidity is greatly over emphasized for temperate climate plants kept indoors. For many beginners, misting is mantra, a way of showing that you care, but many plants could care less. Many tropicals need high humidity, temperate climate plants do not, but it is important not to let levels approach desert aridity, which can happen inside during the winter. Misting plants once or twice a day in my opinion is a worthless procedure. The only thing that happens with misting like this is that you build up salts on the leaves as the water drys. If you mist the entire area around the plant to bring up the humidity, then you are doing something useful, but in the house this is usually not possible. Instead, create humidity by placing your plant on a bed of small stones in a large flat tray filled with water. Do not let the pot actually touch the water. The flatter the tray the better, this will help keep down algae and other critters because nearly the entire volume of water will evaporate each day.

Insect and Disease Control

Insect and disease control will actually begin when you do all the above, because you will have an active healthy plant that will be able to resist them. However, there are bound to be some problems. Watch very closely for spider mites. These are almost microscopic, and can be best seen with a five to ten power hand lens. They live on the undersides of the leaves, so that's where to look for them. Turn a leaf over and look for webbing or debris. A healthy leaf will look absolutely clean (unless you have been misting a lot and building up salts) except for possibly hairs on some species. If you see any debris or webbing at all, start searching for mites. They are little spider-like creatures and they will have very tiny translucent round eggs. Red spider mites are easy to see with the lens and visible with the human eye for those of you with eyes under forty. Two spotted mites are smaller, translucent except for two dark spots on their back, and can even be hard to see with a five power lens, you have to search for them.
Mites, aphids, woolly aphids, mealy bugs, scale, and nearly all potential pests can be controlled if caught early and sprayed with an appropriate insecticidal soap. These soaps may be phytotoxic to some species and cause leaf damage, so try only a few leaves first to make sure. Repeat sprayings are necessary to get the new hatchlings. Once every five to seven days is sufficient if done three times in most cases. For very difficult cases you may have to resort to chemical insecticides. Always follow the instructions exactly. Systemic insecticides can prevent infestations of some species of insects, but you must be aware that you are living in the continual presence of a deadly chemical. This can be of particular concern for indoor plants.
Fungal and other diseases are, in my opinion, more difficult to diagnose and treat. Without an organism, such as insect, to identify, diagnosis becomes very difficult, even for the experts at times. Diseases in plants are most often the result of the presence of an organism, and not the organism itself. This is especially true of fungal diseases. Most fungal diseases of container plants are caused by creating environments more favorable for the organism and less favorable for the plant, so the place to begin is with the environment. If you are getting root rot, shift to better draining soils, water less often, give it more sun (if appropriate), optimize growing conditions to get the roots to quickly colonize the soil. If you are getting leaf fungal diseases, decrease the humidity, stop misting, give it more light and air circulation. If these do not work, seek help in identifying the problem so that you can choose an appropriate fungicide, if one exists.

And finally

Follow these tips and you should be able to grow suitable species indoors for bonsai. It will not be possible to grow every species indoors. You should carefully choose only those with a moderate chance of success. Start out with the easiest, Ficus, a really good tough plant for indoor growing.

How to Reduce the Size of Leaves

by Brent Walston

Introduction

Reducing the size of leaves and the distance between them (the internodes) is the primary focus of the final training of bonsai. This comes after years of developing the trunk, the nebari, and the branches. I have been studying this phenomenon for many years. This is what I have concluded thus far:
The size of leaves, the length of internodes, and the thickness of twigs are related to the:

• Balance of the canopy to the root mass,
• Age and density of the roots,
• Level of fertility,
• Presence or absence of hormones,
• Level of light.

Of these five factors the first and second have the greatest importance for bonsai, but the other three also play a role.

The Balance of the Canopy to the Root Mass

The roots and top growth are in constant cyclical motion to stay balanced. In spring, the roots pump most of their stored energy to produce a full canopy of new leaves, and then shoots for more leaves. In summer the process reverses and the leaves resupply the roots with food, and provide energy for increased top growth. In fall the leaves stop producing food, but food continues to move down the stem from tissues. The roots continue to grow until the soil temperature falls below 60 degrees, using some of their stored food to increase their mass, and yet retain enough reserves to start the process again in spring.
To manipulate growth in bonsai it is essential to be thoroughly familiar with this cycle and all of its ramifications.
If you top prune a tree while it is dormant, you remove outlets, that is buds, for receiving food in spring, the result is the over stimulation of the existing buds, that are released from apical dominance (no more 'stop' hormones from the now cut off terminal buds). This results in long internodes and huge leaves, gigantic whips on some plants like apples and plums.
If you root prune a dormant plant without top pruning, you remove part of the food supply for stimulating buds and new growth. The result is that released buds will form smaller leaves and drastically shorter internodes. Plants seem to know how many buds to stimulate and how much new growth can be supported by the roots. I don't know the physiology, but I have seen it enough times to know that it works. Root pruning succeeds in reducing top growth up to the point that so many roots are removed that water transport becomes critical. At this point, the plant cannot support any new growth and dies. This is called overdoing it.
If you top prune a tree that has just leafed out, you remove the food factory that has just been created with most of the stored energy of the roots. The roots will have to use whatever reserve is left to issue a new set of leaves. This severely taxes the roots, and the new growth will have shorter internodes and smaller leaves. We use this principle in defoliation, although some time is usually allowed to restock food in the roots first. Multiple defoliation will result in ever decreasing leaf size. Liquidambar can be defoliated three times a season if they are in good condition, and are in a region with a long enough growing season.
The manipulations based on this principle allow one to do all sorts of things to control the speed and character of growth. This is the basis for most of the pruning practices used in bonsai.

The Age and Density of the Roots

New roots growing in fresh medium easily absorb water and nutrients and increase their mass very quickly, upsetting the balance in favor of larger leaves and longer internodes due to the excess food stored.
Roots confined in a space tend to get woody and begin to lose their ability to store food readily. One of the first symptoms of a root bound plant is chlorosis resulting from the inability of the aged root system to take up essential nutrients. As the plant stores less and less food relative to the amount of top growth that accumulates, the leaves get smaller and the internodes shorter. This is one reason why these trees are in tiny pots, aside from the aesthetic value.

The Level of Fertility

The level of fertility is somewhat obvious. Plants with good nutrition have normal size leaves and internodes. Virtually no one recommends not feeding bonsai to reduce the size of the leaves and the internodes. However, it is sometimes done to plants in training, particularly seedlings in the first year or two to get a series of close internodes low on the trunk.
Keeping a seedling a little on the hungry side and a little root bound can dramatically shorten the first internodes. This becomes valuable later on in the training process when the plant is trunk chopped to introduce a low curve on the trunk and attain taper. The places where the internodes formed will be dense with adventitious buds which will break easily on most deciduous plants. This is particularly important for the Maple genus, Acer. Most strongly affected by this phenomenon is Japanese Maple, Acer palmatum.
Of all the nutrients, the one affecting leaf and internode size the most dramatically is nitrogen, so it is best to keep the level of nitrogen balanced in the feeding program.

Presence of Absence of hormones

Some hormones can affect leaf size and, particularly, internode length. The most important of these hormones is probably gibberellic acid, which can dramatically increase internode length. These affects have little importance for bonsai.

Light Levels

Plants with good nutrition growing in the maximum of light that they can easily tolerate will have the smallest leaves and the shortest internodes.

And finally

Spend some time reviewing the first two growth principles, and thinking about their ramifications. The answers to most questions about the timing of pruning, and the correct procedure to achieve design objectives can be deduced from analysis of these two principles.
For more information about manipulation of growth in bonsai see the companion article "Using Principles of Growth to Manipulate Plants for Bonsai".

Spider Mites!

by Brent Walston

Introduction

Spider mites are the bane of bonsai growers and growers of ornamentals in gerneral. There are several approaches, incompassing prevention, treatment, and environmental changes. Whether you choose an organic approach or the chemical route, you should find this article helpful. Keep in mind the principles of Integrated Pest Management (IPM):

• Monitor your plants regularly.
• Practice prevention by creating a non conducive environment for pests.
• As soon as you find signs of an infestation, use the lowest toxic level of treatment.
• Move to more toxic chemical controls only if necessary and warranted.

Know The Enemy

First make sure that you have spider mites. Red spider mites are just visible to the human eye and should be easily visible with a five power hand lens. They look like little red spiders. If you look carefully you should also be able to see eggs that look like microscopic pearls. They also make a visible webbing that looks like debris on the underside of the leaf, not on top. If the mites are very small, translucent, and appear to have two dark spots on their backs, you probably have two spotted mites, or one of their relatives. Always look on the underside of the leaf, that is usually where you will find them. Badly infested plants will have yellow and red mottling of the lower leaves.
If you don't have a lens (and everyone should), use a piece of bright white paper under direct sunlight, or a strong lamp, shake the suspected leaves (or needled foliage) over the paper and watch for very tiny specks scurrying to get to the other side. Mites are programed to always go to the underside of the leaf. Mite damage will appear on the lower, older leaves first. Unlike aphids, mites are not interested in succulent new growth.
Mites by themselves are not aggressive movers. They pretty much stay on the same leaf or nearby leaves for their entire lives. They are moved (vectored) by bird feathers, dog and animal hair, and clothing. They are usually worst in dry dusty conditions, although two spotted mites have been known to thrive even under very wet conditions.
Mites have their favorite species, and by learning which plants your mites prefer, you can use these as indicator plants. You can also isolate the preferred plants for treatment if necessary. Plants with hairs on the underside of leaves seem to be a favorite, although not necessarily. Among the all time favorites I have found are: Roses (yum!), Daylilies, Flowering Quince (Chaenomeles), Apples, (Malus), Blackberry and other Rubus, Boxwood (Buxus), and Junipers, but there are many, many other species that are susceptible. Plants grown indoors are especially vulnerable.
Mites usually start becoming a problem in late spring and reach a peak by late summer or just at the peak heat of the season. They are definitely hot weather critters. In cold weather they move and multiply much more slowly. In summer their life cycle is about seven to ten days, that is, hatchlings are laying eggs after a week or two. Any treatment must take this into account. Just killing the adults does little good. Repeat treatments are almost always necessary to kill the emerging mites. In winter they begin moving off trees and shrubs to winter over on grasses.

Prevention

Mites, like aphids are easily dislodged from the leaf surface, at least before they have a chance to begin building webbing. A weekly hard blast of water can stop an infestation from occuring or slow it down once it starts. However, you must be able to spray the undersides of the leaves. Just hitting the top surface will do little or nothing. Concentrate your attention on the lower parts of the plant. Mites won't be found on the upper and succulent parts of the plant.
Introduce predators. Predator mites can be introduced in the spring just about the time the mites begin appearing and building their population. It is much better to use mites this way and have them grow with the mite population rather than to try to treat an infestation with predators. Predator mites are very expensive, so this is also a cost effective procedure.

Treatment

If you find more than an occasional mite, and most of the lower leaves have two or more mites and perhaps webbing, you are probably in trouble. Begin lower levels of control. First try blasting them off with a spray of water. Do this about every two or three days. It may or may not work. If the population continues to build, use an insecticidal soap designed for mites (it should be on the label), or introduce predators.
Safer brand miticide and other insecticidal soaps MUST be tested for phytotoxicity before you use them. Many plants are seriously damaged by these soaps, including most maples. Spray a leaf or two that you won't mind losing and wait three or four days to see if there is any damage. Insecticidal soaps work by contact so there must be thorough coverage. Dunking the foliage may be the best way to treat bonsai and containerized plants. Soaps do not kill the eggs, so they must be repeated every five to seven days. At least three treatments will be necessary. Treatment with predator mites is discussed below.
Once mite count reaches about 40 per leaf, the population will really explode and mites will begin moving to other leaves and plants. In the worst cases, they will even begin moving to other species that are usually resistant. Treatment with predator mites at this stage is possible, but difficult and expensive. At this stage you may want to take a more toxic route.
There are some really effective agricultural chemicals for mites that have a fairly low toxicity. Unfortunately, the over the counter chemicals are the absolute worst products. They are highly toxic and not very effective. I will give you some names below of products that do work, but you should not use them unless they are permitted for your area and situation. The best way to find out what to use in your area is to contact your local Agricultural Extension Agent. It's a simple call, they are in the phone book under county government, usually under Agriculture. They are PAID to do this, don't think that you are imposing on them.
Red spider mites are pretty easily dealt with. You can usually knock them out with water sprays, Safer's miticide (and other insecticidal soaps), Orthene, Kelthane or Isotox, in order of increasing toxicity. These are all nasty chemicals except for Safer's and Isotox may not be available any more. I don't recommend it. The big problem is that there are few effective ovicides for mites, so you must follow up in five to seven days with a repeat treatment to kill the hatchlings. Usually three treatments are necessary to end an infestation. There are one or two ovicides available now, but I believe they are all Ag products, I don't think any are available over the counter. Read and follow all label instructions carefully. Do not use more or less than the recommended amount or concentration. Using less can result in breeding mites with resistance to that chemical.
If you have two spotted mites, your job is even harder. These mites are very difficult to control and most are resistant to most miticides. Don't bother using typical over the counter insecticides, they will do nothing. If they are approved for your area and application, you can use a rotation of Pentac, Mavrik, and Avid. These mites can build a resistance to pesticides very quickly, so repeated use of the same one just breeds new problems for the rest of us. These two spotted mites can still be killed with Safer's miticide. It is highly unlikely that they will build a resistance to this, but you must have physical contact with the miticide, so be sure to dip your plants or thoroughly spray them. Follow up treatment twice, at five to seven days. Always use pesticides as recommended. Solutions more dilute than recommended will not work and promote resistance.

Predator Mites

I fought mites for years before I started using predator mites. It took almost two years for them to get back into balance with the mites, but since then, I haven't sprayed once. That was five years ago. Spraying took me all day and cost over a $1000 a year. Now I have that extra day to do meaningful work and save the money. Mite damage is zero. The key was to decide to stop spraying. Once you introduce predators, you must stop spraying to let the environment come back into balance. While this is happening, you just have to live with the damage until the predators gain control.
Critics have said that while predators may work in a nursery situation, it won't for bonsai or in a small yard as long as your neighbors are engaging in chemical warfare. I think it is worth a try as long as you have a yard that will provide a complete environment, which usually means some exposed soil, trees and shrubs. In fact predator mites are more useful to small scale operations, than to larger ones such as mine. They can be used to treat individual plants, but long term control means changing the environment, including establishing a population of predators.
You must choose the right predator mite for your situation. There are several species available that are adapted to a particular climate. They have a rather narrow range of humidity and temperature requirements. I needed the one that tolerates high temperatures and low humidity, which is M. longipes (M.l.).
Predator mites are available from several bio control companies. I got mine from my local farm supply, the company is Nature's Control, but I don't know if they are mail order or if there is a website.
The other company is Green Methods. These folks put out a fabulous descriptive catalog with just about everything you ever wanted to know about mites and their predators as well as dozens of other pests and controls. They sent me one free, but the catalog has an advertised price of $8.95 (worth it). Their phone number is 603 942 8925. As of this writing they expected to have a website up in February 2002:
http://www.ShopGreenMethods.com
Predator mites are expensive. In fact, on a weight basis, probably the most expensive thing I have ever bought, somewhere in the neighborhood of $500 a gram, or $50 to $80 per thousand mites.
Effective treatment is dependent on getting the proper predator mite. Green Methods lists about six, Nature's Control lists three. The most important parameters are temperature and humidity, but there are also other factors such as fast knockdown, early introduction, longevity, etc.
If you have ONE infested plant, I'd say forget it, the mites would cost as much as the plant, but if you have a good size collection and mites are a general problem, including your landscape, it might be a feasible method of control.
Additionally, yes the mites do stick around because bio controls do NOT eliminate the pest but simply set up a dynamic between the two species which keeps the pest from getting out of hand. If you want total control (read elimination) you must use chemicals. But this is also a panacea because the total elimination is short lived, which puts you in an endless cycle of spraying.

And finally

Again, let me emphasize, that pesticide spraying for mites is not the answer, it is a short term solution. If you are ever to gain control of a persistent problem, you will have to bring your local environment back into balance, which means spraying will have to stop. Give predator mites a try.

Root Heat in Containers

by Andy Walsh

Introduction

This was originally a post from the Internet Bonsai Club where Andy is a frequent contributor. Andy was asked if direct sunlight shining on black plastic nursery containers could heat up to the point of damaging the roots. In typical fashion, he replied with a most complete and thoroughly researched answer.

Trees in the Earth

High temperatures can seriously damage the roots of plants kept in containers.
As I'm sure you are aware, the roots of trees in nature normally experience a fair amount of temperature variation. As the feeder roots of trees tend to inhabit the upper 1 foot or so of the soil, they are affected by the increase in temperature that this layer of soil experiences from direct sun and ambient air temperatures. These effects rarely go below about 1 foot and the effects drop off with the depth.
In "Soils: An Introduction to Soils and Plant Growth" (Donahue, Miller, and Shickluna) Miller shows a chart of air temperature and soil temperatures at different depths throughout a day in July in Utah. At 12 noon the air temp was about 97F and fell to about 60F at midnight. By about 1pm the soil at a depth of 2 cm reached a peak of about 93F. At 10 cm deep a maximum of about 85F was reached at about 6pm. At 30 cm it only budged up to 75F at midnight. All the soil temps dropped off into the mid 60's to 70's overnight. This kind of temperature movement of the soil is fairly common in most areas. These authors offer a (not so accurate) rule of thumb to find the mean average soil temperature for your area: add 1 degree C to your mean average air temperature. This could be loosely applied to monthly averages also. This should give you an idea of what temperatures your local trees root's see in the soil in your area.
So it's obvious that some tree roots can see fairly high temperatures in nature. However, in a deep forest little sun reaches the forest floor and root temperatures are probably fairly low and more constant. This probably holds true for most lightly wooded areas such as my backyard also. (I'm sure all of us are aware of how much cooler the ground is when sitting in the shade of a tree). I would venture to say that many tree's roots are used to seeing moderate temperatures and are not used to high temperatures.

Trees in Containers

In the world of container culture of trees the situation is a bit different. The same wide temperature variations occur as described above but they can be much more exagerrated. The roots of trees in containers do not benefit from the buffering action of the surrounding soil. In most cases the roots are just on the inside surface of the pots and can be quickly and easily affected by direct sunlight and air temperatures.
Dr. Carl Whitcomb in his book, "Plant Production in Containers" cites some research showing that very high temperatures can be experienced by roots in containers. One researcher in So. California found that soil temperatures in black plastic containers reached a maximum of 115F and remained at or above 100F for 5 hours each day that they were observed (Harris, R.W. 1967 "Factors influencing root development of container grown trees" Proc. Int'l Shade Tree Conf. 43:304-314). Some researchers in Mississippi also measured the temperatures of black plastic containers in a bed of plants and found temperatures in excess of 120F near the sides of the containers and 100F in the center of the containers on one edge of the bed. Containers located in the middle of this bed, for instance, had temperatures less than 90F. In this study the containers were closely arranged providing a solid canopy of foliage which shaded the inner containers. (Rauch, Fred D. 1969 "Root zone temperature studies" Miss. Farm Research) Generally, this will be the case in nurseries that typically arrange plants in beds to maximize space. Bonsai on the other hand are normally spaced far apart to assure that all branches get sun. Therefore the roots of trees grown as Bonsai will normally see the higher temperatures.
Although it is generally accepted in the nursery business that high temperatures are responsible for poor growth, there is little documentation on the species specific effects of high temperatures. There are some studies available though; for instance, Loblolly pine (Pinus taeda) was found to show maximum root growth at temperatures between 70-80F with growth reduced as much as 90% at 95F. This same study found that a number of conifers were killed in a few hours at 117F (Barney, C.W. 1947 "A study of some factors affecting root growth of Loblolly pine. Pinus taeda" PhD dissertation. Duke University School of Forestry). Although there are only a few more studies to go on, it is not a tremendous leap of faith to assume that most temperate tree roots probably have growth optima in the 70-80F range also. Higher temperatures probably slow or stop their growth, and maybe kill them as well.

Shading the Containers

There is also some information on the effects of shading containers on root growth. A study was done where containers were shaded at levels of 0, 30, 46, 64, and 100%. Four woody species were used: seedlings of Austrian Pine and Mugo Pine, and rooted cuttings of Japanese Garden Juniper and Chinese Holly. Roots were examined, counted, and graded before the study and after 6, 12, and 18 days. The study found that the higher the % of exposure the higher the root damage, and, that the most damage occurred during the first 6 days. The Junipers were the most affected losing 88% of their roots after the first 6 days. The Hollys were at 72%, the Austrian Pines at 48% and the Mugos at 40% after 6 days. The author did not indicate what % exposure these numbers came from. (Whitcomb, Carl E. and George W. A. Mahoney 1984. "Effects of temperature in containers on plant root growth" Okla. Agri. Exp. Sta. Res. Rept. P-855:46-49). Whitcomb shows some stark photos of the effects on roots from this type of exposure. On the exposed sides of containers there are no roots at all. On the shaded side there are plenty of roots.
Whitcomb states that "This study shows that heat stress on plant roots in containers is a serious problem. The rapid loss of roots following exposure correlates with the abrupt plant stress frequently observed when container-grown plants are spaced during the summer. Roots killed by heat are prime sites for the entrance of root-rot disease organisms. Root death from high temperatures may be a major factor in providing an easy entrance to root diseases".

Color of the Containers

There have been some studies on replacing black plastic with white plastic but while white containers do reduce the soil temperature, the white polyethylene becomes brittle on UV exposure and falls apart. But in general, the lighter the color of the containers the less the effect from sunlight. Something to consider.

Heat Damage

I have thought about this issue many times over the years as I have noticed that some trees that I have kept up on my growing benches seem to languish in the hot summer sun where ones of the same species that I have crowded together on the (cooler) ground "seem" healthier. I have often suspected that summer heat damage might have been responsible for the loss of some of my stock plants in the winter.
Root rot usually occurs in the summer and is invariably blamed on poor drainage and overwatering. I wonder how much root death from overheating may also contribute to the summer root-rot phenomenon. (It's almost ironic that it's recommended to place Bonsai affected by root-rot in the shade after treatment - part of the cure?) Even some of the winter occurrences of root-rot may have had their origin in summer heat killed or damaged roots. (Now, there's some interesting studies to be performed).

And finally

I think it's fair to say that high summer temperatures and placing Bonsai in full sun throughout the growing season probably have some negative effect on a Bonsai's roots. Precautions such as midday shading and watering to cool down the containers might be in the best interest of a Bonsai, and I have even seen these things mentioned in some Bonsai books. (I may even rethink the layout of my growing area and move some trees to more shade in the deep summer).

Root Grafts for Bonsai

by Brent Walston

Introduction

Grafted plants for bonsai often present problems in the training stages, or later as the plants get older due to differing rates of growth between the root stock and scion and because of differing bark characteristics. This can be overcome by using cutting grown material whenever possible, or by using special types of grafts that will minimize the problems.

Avoiding Grafts

I try to avoid grafts for bonsai whenever possible. It is almost always better to have a plant on its own roots than grafted to a rootstock. Cutting grown material is becoming much more common for bonsai suitable species and you should look for it to avoid the problems of suckering and rootstock scion mismatch.
Suckering problems occur in such genera as Liquidambar, Malus (apple), Pyrus (pear), and Prunus ( cherry, plum, apricot), Crataegus (hawthorn), and others deciduous woody plants. Profuse suckering leads to endless pruning and bud rubbing to keep the suckers from overrunning your cultivar. The problem is particularly bad after major pruning, for example, after a trunk chop to get a low curve and taper to the trunk. Sometimes the scion will actually die and the understock will take over the plant after such drastic pruning.
In addition, there is often an unsightly graft union in these plants. The differing bark characteristics can make the union stand out dramatically and detract from the trunk, and the illusion of an ancient rugged tree. Growth rate mismatches can often lead to a 'necked down' appearance for smaller dwarf cultivars on standard rootstocks, exactly the kind of plants we are looking for in bonsai. Even worse is the problem of the scion growing faster, resulting in REVERSE taper. Prunus species often form a burl at the graft union that is prone to insect damage and completely unusable for bonsai purposes.
Most of these species can be grown from cuttings without too much difficulty. Some are extremely difficult, such as cultivars of Crataegus (hawthorn). Crataegus laevigata 'Paul's Scarlet' cuttings will sometimes take three years to root. It is also possible to air layer many of these species to get them on their own roots.
Conifers present the larger challenge. While most Juniperus, Chamaecyparis, and the broad leaf evergreens can be grown from cuttings, it is the pines that pose the greatest problems. Some pines can be grown from cuttings, but it is almost always easier to graft them.

Root Grafting Pines

Japanese White Pine, Pinus parviflora, make particularly bad grafts, especially the dwarf cultivars since the understock soon outgrows the scion portion and necks down abruptly. Sometimes they are grafted onto Japanese Black Pine, P. thunbergii which of course has totally different bark. If this is done for effect it is usually grafted about four inches up and the trunk bent at the union. It gives the appearance of great age but the abrupt transition of bark types has always bothered me.
Other than this style, the grafts should always be low. It is very difficult to obtain low grafts. 99% of the pine grafts are made for landscape and not bonsai, so it takes a nursery dedicated to bonsai or one which is sensitive to the needs of bonsai enthusiasts to produce good bonsai grafts. A few large nurseries that produce the bulk of grafted pines in this country have been persuaded to produce some grafts for bonsai, so things are beginning to change.
The very best grafts are 'root grafts'. The scion is not actually grafted to the roots, but rather to the stem tissue below the 'crown' that forms when the seed emerges from the shell. This is a small ring of tissue on the stem that clearly marks the division of root type tissue (was the radicle of the seed) and the true stem which is capable of producing foliage. On pines and cedars this 'root' portion of the stem can be very long, as much as six inches or more before actual roots appear.
For bonsai the seedling understock is potted up high so that the root portion of the stem stands several inches above the pot. This makes is easy to do a low graft. The graft can be placed just below the crown ring and after the graft takes, about a year later, the whole thing buried so that the graft sits right at the soil line. Since the buried stem portion is root tissue it can stand this procedure and has the possibility of forming roots. Grafted in this fashion the union will blend perfectly into the nebari (crown and surface roots). Also, since there is usually a bulge for dwarf cultivars, what was once a liability now becomes an asset since the swelling will be right at the crown.
If your graft is below this ring of tissue, you may bury it up to the graft. If it is above the crown ring you can still bury it, but you must be much more careful. It is akin to air layering. Bury the stem section in sand after making some vertical slices in the stem where you want roots and treating with hormone. This will work for all pines that are 'low grafted', that is have a graft only an inch or so above the crown ring. If the pine is 'high grafted' it will have to be air layered.
I recently went to a local bonsai nursery and checked out the potted up White pines and the grafts were hideous. Very nice little styled trees, a dwarf cultivar, grafted onto white pine with the understock about twice the diameter of the scion with no effort to conceal the graft.
This procedure also applies to Japanese Black Pine cultivars, Pinus thunbergii, as well, and is especially important for the rough bark ones. There is nothing more ludicrous than a nicely styled Nishiki Kuromatsu with two inch bark wings floating above a relatively smooth lower understock section. To get really picky, the very best rough or cork bark black pines will be grown from cuttings so even the surface roots will show the corking. I have a rough bark Japanese Maple, Acer palmatum 'Arakawa' that has such corked surface roots (cutting grown). It is quite amazing.

The photo to the right is a root graft of Pinus thunbergii 'Kyokko', a cork barked Black Pine (Nishiki Matsu). A graft this low will allow the corky wings of this cultivar to blend perfectly into the nebari. The arrow indicates the ring of tissue dividing root from stem. The graft has not yet been tied. Click on photo to enlarge.

A little more information on identifying the crown ring. Look low on the stem, or uncover the stem by removing some soil and look for a point where the bark changes texture. For pines and cedars the root portion usually is smooth except for little bumps. Above the ring, which is usually a slight swelling, the bark is usually ring like. Try looking at cedars first, since it is unmistakable on them, and then on a pine. This feature usually disappears after a few years as the root portion attains mature bark if it is above ground.

Factors that Influence Watering

by Brent Walston

Introduction

I like to check for dryness by lifting the pot. It takes some experience to develop the 'feel' of a dry bonsai, but it works quite well. It is amazing how much an adequate amount of water will increase the weight of the pot. Of course this is only possible for smaller plants. I don't go around lifting 5 gallon cans to see if they are dry, or the monster bonsai. But since about 25% of the volume of a proper soil mix is water at the saturation point, this is a significant increase in weight, and one needs only to pick up a pot when wet, and then when dry, to tell the marked difference. Dryness can also be tested with a chopstick inserted into the bonsai pot as a sort of dipstick. When the chopstick is pulled out and it is nearly dry, it is time to water. This is a method advocated by Michael Persiano. A third method, perhaps used by most people, is to dig half an inch under the soil surface. If it is dry down to this point, it is time to water.
There are several factors that affect 'drying time' and they are all interrelated. For example, Malus and Prunus can tolerate denser soils under optimum conditions because they grow so quickly that the roots soon colonize it. This rapid top growth quickly pulls the water out. I have to prune all the time of course, so when I cut them back to form a new trunk section, they are now too wet until the top grows back.
Here are some of the factors I have found that influence the drying time:

Soil Mixture

The primary components holding water are: organic and inorganic fines (very small particles), peat moss, vermiculite, and clay. If you increase the amount of any of these amendments to your soil mix, you will decrease drainage, and increase the water holding capacity of your soil, which will increase the interval between watering.
Increasing the percentage of these elements to the point that the soil will hold more than 25% of its volume as water is not recommended. Beyond this point you may begin having root rot problems form decreased aeration (poor drainage).
The components that increase drainage (aeration) and reduce water holding capacity are: inorganic and some organic (bark) large particles (greater than 1/8 inch). These include lava rock, coarse sand, perlite, turface and other stable fired clay products.

Plant Size and Pruning

Fast growing leafy species colonize rapidly, drying out the soil. Root bound or even properly root colonized plants will dry a pot very rapidly. This rapid drying of the soil is very healthy for the plant, if you manage to water often enough. Each time the plant dries out it pulls a fresh charge of air into the root zone. Likewise, each time the plant is watered and the excess water drains, another fresh charge of air follows the water to through the root zone. I consider the ideal watering interval during the growing season for outdoor plants to be one day. This makes watering easy to remember or schedule, and will almost assuredly prevent root rot problems. Cycles shorter than one day inevitably lead to dry or wilted plants on occasion.
Plants that are well root colonized in the pot shorten the watering interval as the top grows and demands more water. After a plant is top pruned, transpiration is decreased and the watering interval is again increased. For plants that are very susceptible to root rot, it is important to pay close attention to this factor.

Fertilizer

By affecting how fast the plant will grow, fertilizer can accelerate the drying time. It can also speed the decomposition of the organic portions of the soil, causing premature soil collapse which increases drying time and slows growth. Soil collapse due to decomposition is a much overlooked factor in plant growth, and water intervals. It can be avoided by using a higher percentage of stable inorganic material and high quality organic material such as fir or pine bark. Decomposed wood fiber products other than bark decompose very quickly and are generally unsuitable for bonsai. The same is true of garden or other compost.

Disease

Root rot will decrease the ability of the plant to take up water and slow the drying time. The symptoms of root damage can be very misleading. There are several diseases that cause the blockage of the plant's vascular system, preventing it from taking up water. The outward symptom is the wilting of the leaves. The natural inclination is to water the plant, but the problem is not a lack of water, it is the inability of the roots to take it up. This leads to overwatering which severely exacerbates the fungal problem. The solution is to let the plant dry out, not to water it. Whenever a plant wilts, first make sure that the soil is dry before watering it. If it is not dry, this can be a symptom of a fungal infection of the roots.

Wind

Wind will increase transpiration and decrease the watering interval. Strong winds, under even moderate temperatures, can very quickly dry out a plant. Some plants are much more vulnerable than others. In general you should not place bonsai in an area that receives prevailing winds. This can even be a problem in winter when the soil is frozen around the plant's roots. The roots cannot absorb water under these conditions, but the foliage and stems continue to lose water. It is very important to protect plants from wind under these conditions, and to make sure your plants are thoroughly watered before the onset of cold drying winds.

Sunlight

Sunlight will heat the plant and the pot, increasing transpiration and evaporation, decreasing the watering interval.
Bonsai grown in the hottest and driest areas of the country need to be located where they will get morning sun and afternoon shade. The fastest growth will occur where there is bright light and optimum (moderate) temperatures, so there is little growth loss for most plants by placing them in the shade in the heat of the afternoon.
Optimum light levels will result in the fastest growth which will also decrease drying time by promoting increased foliage.

High Temperature

High temperature will increase transpiration even in the absence of sunlight and decrease drying time. Temperatures above 80F, with morning to full sun, and moderate to low humidity, will usually mean watering every day for most established container plants (and bonsai).

High Humidity

High humidity will decrease transpiration, and moderate high temperature, which will increase drying time. Increasing humidity can be a valuable part of extending the watering cycle in hot dry climates. In our area, I can avoid watering twice a day by giving the plants one or two short (several minute) bursts of fine spray during the heat of the afternoon when the temperature exceeds 100F.

Pot Size

An extra volume of soil increases the reservoir of water and increases the drying time. For very fast growing, water thirsty species such as Salix (Willow), this is a must.

And finally

Many of these factors may be manipulated to control the drying to suit our conditions. I feel that the ideal drying time is one to two days while the plants are actively growing.

Root Pruning

by Brent Walston

Introduction

Root pruning is an integral part of bonsai. No plant can stay in a container indefinitely without some sort of root work. In this article I will discuss the mechanics and timing of root pruning for bonsai.

Why Root Prune?

Plants are constantly in search of new water rich, nutrient rich material to grow their roots. In the earth this is no problem, roots can travel many tens of feet from the plant stem in search of nutrients and water. In a container the situation is totally different. Roots tend to 'colonize' an area or container. That is, they saturate the container with roots. In some cases they even will push the plant upward from the container by the sheer volume of new roots. When this happens the plant is said to be root bound.
If root bound plants are not top pruned they will quickly dry out on a hot day, requiring more than one watering per day. Top pruning the plant will help with the water storage problem by reducing transpiration, but there will be additional problems if the plant is not also root pruned.
Plants seem to need fresh new root growth in order to adequately absorb major and minor elements from the soil solution. In fact one the first symptoms of a root bound plant is a general chlorosis despite the fact that it is adequately fertilized. Root pruning and repotting a root bound plant will invigorate it and cause a flush of new growth.
Another symptom of a root bound condition is a loss of vigor, even under ideal conditions and adequate fertilization. The leaves will be very small and the internodes very short. Of course this is exactly the type of growth that we desire in bonsai, and we achieve it by keeping roots constrained in these tiny pots. However, growth is not a static condition, and if plants begin to generally decline it is probably time to root prune and repot.
The object in bonsai is to keep trees dwarf and approximately the same size once they are finished. This means that they must be root pruned and repotted back into the same pot with new soil periodically. Of course another important aspect of bonsai is creating them from collected material or nursery stock. Here, the roots must be substantially reduced as part of the training process to get them into the final desired bonsai pot.

How Often to Root Prune

The frequency of root pruning is related to a) the species, b) the container size, and c) the environment. The bottom line is that a bonsai should be root pruned and repotted when it shows symptoms of decline and/or chlorosis as described above, or when it begins to push out of the pot.
Some species are simply just slow growing and will require root pruning and repotting less often. Other species grow at a phenomenal rate and may require root pruning and repotting more than once a year, such Salix (Willow). Many flowering species are quite vigorous and require yearly repotting to maintain vigor with profuse flower and fruit production. These include Malus and Prunus, apples and plum, cherry.
In small containers most plants will colonize the pot within a single growing season. This is especially true of mame (very small bonsai). Nearly all mame should be repotted every year. Shohin (under ten inch bonsai) should be repotted every year to two years depending on the species and the growing conditions.
Large potted specimen plants may be root pruned and repotted every other year to as long as ten years depending on the species. Many large pines are comfortable with five to ten year root pruning programs. Cedars and Spruce may be similarly treated.
Plants grown under less than ideal conditions will of course grow more slowly and require root pruning and repotting less often.

What Time of the Year to do It

Root pruning damages a plant, restricting its ability to take up water and nutrients. Therefore it must be done at times of the year that the stresses on the plant are minimal. For temperate climate plants there are two times of the year that these conditions are optimal, late fall and early spring. Tropical plants can usually be root pruned and repotted during periods of 'quiescence' or slow growth.
In late fall, deciduous plants have stopped supplying leaves with moisture, evergreens are slipping into dormancy, ambient temperatures are cooling, heat stresses are gone. Contrary to this cessation in activity to the top portions of the plant, the roots are once again becoming alive with activity. They have stored an entire season's supply of food and the upper tissues are still moving food down to the roots. Growth of roots is not dependent on light, only on the supply of food and soil temperatures. Eventhough air temperatures are slipping in the fall, soil temperatures remain higher since the days are still warm and the warm earth is still radiating heat. This is especially true for plants that are in the ground, or in contact with the earth.
As long as the daytime temperatures are above about 55F during the day the roots are in a flurry of activity. If you root prune during this period, there will be a new flush of root growth before temperatures fall into the winter range. This is especially true of mild climate areas of the West Coast and the South. This means that cut ends will heal over quickly and that new root growth will proceed until the temperatures dip.
In the spring the temperature stresses are also low so that root pruning will not cause excessive transpirational losses. In deciduous trees the leaves have not yet formed so there are no losses there. In evergreens the foliage is intact but the temperatures are low enough that there is no heat stress. Spring is a time of rampant plant activity. The dormancy requirements have been met and the increasing air and soil temperatures insure that both top and root growth are soon to follow. At this time the roots reverse the Fall process of storing food and begin to pump food and water up to the buds and stems.
The buds already contain enough food to expand into leaves if the roots can pump up enough water to open them. This phenomenon allows for a unique period of root manipulation. If a plant is heavily root pruned during this period the buds will open but new shoots will not expand. This will limit transpiration and the following photosynthesis from the opened leaves will restore the food lost from the root pruning. I have used this principle to root prune bare rooted field grown seedlings (seeRoot Pruning Bare Root Seedlings). This removes the tap root and starts the shallow root system so desired in bonsai.
Plants can also be root pruned and repotted at times of the year other than the foliage dormant periods. In these cases particular attention must be paid to the transpiration/ root capacity equation. That is, the roots are responsible for supplying the plant with moisture and minerals, not carbohydrates during the growing season. Any root loss results in consequential loss of moisture to the upper parts of the plant. Put simply, they will wilt. Pruning during the growing season must also be accompanied by a commensurate amount of top growth to balance the water equation. If you remove too many roots and not enough top growth, wilt and death can result. A good general rule of thumb is to remove the same percentage of top growth as root growth.
I have used this principle to collect California native oaks out of season (June) and apples as well. With experience one may root prune and repot at any time of the year under the right conditions by manipulating the environment. But beginners should stick to the safe periods of fall and spring.

Manipulation of Growth Through Root Pruning

Root pruning can a very valuable tool in the bonsai training process. By carefully timing the root pruning and the top pruning of a plant, growth may be either slowed down or speeded up. The character of the growth can also be manipulated. Dormant root pruning without top pruning will result in food storage losses and the resultant top growth will be weaker with small leaves and close internodes. Dormant top pruning without root pruning gives the opposite effect. This will reduce the number of buds and sites for growth and will result in larger leaves, long intenodes and rampant coarse growth. For more information on this topic see Growth Principles.

How to do It

Root pruning a container plant is a relatively simple process. Simply unpot the plant and proceed to comb out the roots in a radial pattern. There is one superior tool for this process, the root hook. This is a single tined tool similar to a hay or meat hook. It will untangle and straighten roots with a minimum of damage. They can be purchased or easily made at home. Small plants may only require chopsticks to do the job.
The larger thick roots should be sacrificed at the expense of the smaller fine and hair roots. These smaller roots are much more efficient at absorbing water, the immediate necessary factor following root pruning. In the case of pruning nursery container plants in order to move them into bonsai pots, a substantial amount of roots must be removed. Bonsai plants require a substantially shallower root system than nursery plants. This means that the lower portions of the one gallon or five gallon can must be totally removed.
Very often it will not be possible to move from the nursery container to the bonsai pot in one step. In this case remove as much of the root ball as safely possible and repot to a smaller, shallower training pot. After a year or two it should be safe to further root prune and shift to the final bonsai pot.
When severe root pruning is required to get a nursery plant into a bonsai pot, I use tools such as an axe or sometimes even a chainsaw to remove the lower portion of the roots. To be on the safe side do not remove more than two thirds of the roots of a container plant if root pruning during the dormant season. Severe root pruning should only be done during dormancy. There is no substitute for experience in guiding you here. Start root pruning conservatively and only progress to more severe pruning as you gain confidence.
If the plant was in a fairly good nursery mix with coarse materials, it is not necessary to completely remove all of the old soil, although most of it should be removed. When plants are collected from native earth during the dormant season it is probably best to remove as much of the heavier material as possible to make the transition to container mixes. This heavy clay material will hold far too much water in container culture ( see Soils for Containers and Bonsai) . It is tempting to blast the root ball with water to remove the old soil, and for some species this is perfectly acceptable, however it does cause more damage to the fine root hairs than combing out the soil.
Remove the circling roots, the thick tap root remnants under the crown and shorten larger storage roots. Try to keep as many of the fine roots as possible. The roots should be trimmed all around so that the root ball will fit into its new container with having to fold or tuck long roots into it. This is also a good time to start looking at the nebari and deciding if any of the surface roots need to be removed for aesthetic reasons. Place the root ball on a shallow pad of new soil in the pot and proceed to dibble more soil into all the spaces between the roots with a chopstick. Keep poking holes until there is a slight resistance, this means the voids have been filled with soil. Lightly tamp the soil surface and water thoroughly. This first watering should saturate and flush the soil. Water two or three times longer than you normally would to settle the soil and wash out the fine material.
You can finish by placing a layer of heavier gravel or decomposed granite on top, applying moss, or both. Then water again.

And finally

Root pruning can be the scariest aspect of bonsai culture for beginners. It is very difficult to explain how to do it with words. The above guidelines should help, but the best thing to do is watch someone do it before attempting to do it yourself. This is where a bonsai club can really help. If you cannot locate a club in your area, see if you find someone with experience who can help you the first time. After this, take small steps to gain confidence and you will be soon have the craft mastered.

Olive for Bonsai

by Marco Favero

Introduction

Olea europea sativa or Olea europea oleaster are outdoor trees. The name olea derives from the Greek word Elaila. Olive has been here in Europe from the tertiary period and the Phoenicians were the first farmers of this tree.
In the Bible, Noah, after the Deluge, saw a dove with an olive branch in its mouth like the symbol of peace between God and men. Olive is present in many books of Hebrew, Phoenician, Egyptian, Greek, and Roman authors. Pliny the elder in his Natural history (Naturalis historia-37 volumes-died in 79 A.D. because he approached too closely to the Vesuvius eruption at Pompeii) distinguished 15 varieties of olive. In the parable, Judges book (9: 8-9) one reads: As the trees set out to consecrate one tree as their king, they said to the Olive, "Reign thou over us" and the Olive answered, "Should I leave my [oil], wherewith by me they honour God and man, and go to be promoted over the trees?"

Native Habitat

Olive is endemic to the Mediterranean, from the center of Italy and south, but also in the great lakes of the pre alps. Acid and alkaline soils are not a problem for it. It can tolerate hot, dry weather and also hot and cold winds. It grows slowly, but strong; and can achieve great age, as it can resprout from its trunk, even if you cut or burn it. Olea europea can live in favorable conditions even to 1500 m. (4,926 feet about). There are some specimen in the Algerian Sahara, and in the Hoggar mountain area, Olea Laperrini occurs at 2500 m. (8,107 feet) as a magnificent example of adaptation to foreign a environment.

For Bonsai

For bonsai, the weak point of olive is cold tolerance, because it produces many fine roots that do not withstand protracted frosts. Leaves bear temperatures between 6 or 8C (43 or 46F), in colder zones it is better to cover soil with mulch or put it in an unheated garage. For soil, use 1 part Akadama, 1 part sand, 1 part peat. Also acceptable is 1 part sand, 1 part leave mold, 1 part peat. It is also desireable to add some form of limestone (Dolomite for example). The soil must be porous and be able to retain moisture.

Growth Habit

There are three growth stages in the life of olive: childhood, youth and maturity. In childhood, olive grows only by a taproot, dedicating most of its vigor to form a trunk. Where there are cotyledons, this stage lasts 7 years and some callusing on the trunk can develop.
In youth, olive sprouts a second generation of roots that increase in proportion to the number of trunks. The crown is often unpleasantly enlarged with one or many great roots, while fine roots are deeper.This stage can occur in only one year with an air-layer of the trunk.
In maturity, olive stops to sprout deep roots and also grows out many fine superficial roots. The trunk loses its cylindrical shape, while bark becomes smooth to rugose and cracked. From this point it can live 800 to 1,000 years with a stately appearance.

Propagation

Propagation from seeds is very difficult, with a 30% germination rate at the end of winter. It can be grown from cuttings with a diameter of 3cm (about 1 inch). The best time is the third waning moon, i.e. when olive gets ready to reawaken from winter. If the cutting is from 3 cm to 7 cm (2 to 3 inches) in diameter, a better time is two waning moons of fall with branches without leaves and with at least 5 nodes.

Pruning and Shaping

Olive has a bad reputation with regard to pruning. When a substantial stem is cut back the new growth is coarse and vigorous at the cut. The best time for pruning to shape is the fall, when there is waning moon, especially if the branches have a diameter larger than 3cm(1 inch). If one prunes in the spring or summer, there is a risk of inverse taper in this area due to the resultant coarse, congested growth. Eliminate buds in this part to minimize this effect. The second pruning to shape is accomplished after the spring and fall growth before a new vegetative cycle begins. Eliminate buds that grow up or down, in order to have alternate ramification to right and left of the principal branches.
Pinching differs according bud colors and age of the tree and the cycle of growth. The new buds and stems are usually green, violet or tan. In young trees, one cuts to the first or third set of leaves, according to the direction of the buds. When stems turn from violet to tan it will grow only a few more buds. With young and old trees, you pinch when the branch is still green or is almost violet, eliminating last couple of leaves. Also pinch out leaves and buds that grow downward . Stop pinching if the temperature is down to 10C (50F) or up 40C (104F). By pinching in this fashion you will have smaller leaves and shorter internodes. Generally, almost all the leaves that are on green stems ramify less than half as much as those on the violet stems.
Wire young trees and stems that are only 2-3 years old. Wire carefully from late fall to spring, and only as necessary to control the branches, olive wood is soft and easily damaged. In aged trees, wire is applied to older branches, but it is good idea to use raffia during dormancy.

Culture

Repot in the spring when buds sprout, removing 1/3 of the roots and eliminating old leaves by 1/3 every 2-3 years.
Water thoroughly, but to let it go dry after each watering, but not too much. My olive is watered a lot, but in each case, this depends on light, wind, humidity, and exposure. Olive prefers to be in full sun.
Feed with organic food with slow transfer, but use a normal feeding like others trees. It is also important to add trace elements at least once a year. This can be done with the use of a complete fertilizer with trace elements, or trace elements by themselves in time release form.
All styles, except formal upright and exposed roots, may be used. But employ no jin or shari because the wood cracks and decays quickly.
Pests and diseases include green aphids (especially if you have ants), red spiders mites, anthracnose, and Pseudomonas savastanoi.