Crabapples for Bonsai

by Brent Walston

Introduction

Flowering Crabapples, Malus species, and cultivars are one of the best flowering trees for bonsai. They are covered with beautiful flowers in early Spring before the foliage appears and little green apples appear in Summer, ripening to all different colors in the Fall when the foliage begins to turn to shades of yellow, orange and red. Winter brings a nice twiggy skeletal outline punctuated by the persistent fruit. New cultivars are constantly being developed giving us an ever increasing selection of flower color, fruit color and size. They are easy to grow and quite pest and disease resistant.

Cuttings versus Grafts

The problem of using Crabs for bonsai up to now has been the difficulty in obtaining good low grafts. This has been solved by growing Crabs for bonsai from rooted cuttings. There are only a few people doing it, but cutting grown crabs can be obtained from several mail order nurseries now. Grafted crabs suffer from unattractive and often mismatched unions making an imperfect trunk line. You can try burying the understock an inch at a time by making vertical slices in the bark and applying hormone, then covering the area with good bonsai soil to try to move the root zone upward. You may also try air layering. Budded crabs have about eight inches of straight understock trunk with the scion making a right turn at the union.
Additionally there is the problem of understock suckering. Whenever the top of the plant is pruned, the understock is very often stimulated more than the scion resulting in an explosion of sucker growth. This makes large trunk crabs very difficult to train.

Cutting Propagation of Cultivars

Most of the cultivars are quite easy to propagate, but the conditions are very specific. Unlike other members of the Malus genus, Crabs do not usually root from hardwood cuttings. They must be propagated from semi-hardwood cuttings taken from June through about early August. For some reason talc based hormones work better than solution formulations. The usual hormone strength (IBA ) is 0.8%. If you have a place at home that stays shady, cool, and damp you might try some. Take 6 inch cuttings, remove most of the leaves by cutting off about 3/4 of each one, dip in hormone and place in a clean flat of 4 parts perlite to one part peat and loosely cover with plastic. Do not let them dry out. They will root in about 4 weeks.
Unfortunately the cultivars of Malus coronaria do not easily root from cuttings. They callous nicely, but I have never rooted a single cutting. I particularly like this species because the flowers are very fragrant. One cultivar, 'Klehm's Bechtel Improved' is extremely fragrant, the sweet but not cloying perfume can travel many feet from the tree itself. This is my personal test for fragrance, if I have to stick my nose in to smell it, I don't consider it to be very fragrant. 'Bechtel' is also one of the few truly double flowered Crabs. The pink buds look like little roses. It also blooms much later than other Crabs, waiting until May when the foliage has already covered the tree. I am currently low grafting this cultivar.
Another interesting aspect of growing Crabs from cuttings is that the plants are much more vigorous. This isn't really noticed until you put them into the ground to fatten them up. I find that the cutting grown specimen grow 2 or 3 times as fast as the grafted ones.

Training Young Material

Once you have the trunk development you desire, then it is time to put them in bonsai pots.
If you put a pencil thick cutting in a bonsai pot you, you will have to wait many years to get a one inch trunk tree. I begin training cuttings immediately. They grow very fast in training pots, and require pruning only weeks after being potted up. As soon as the roots fill the little plastic pots, I cut back the leader to about three inches, leaving a section of close internodes if possible. This facilitates growing and choosing low branches later on. Multiple trunk cuts will also make nice soft, or sometimes radical bends in the trunk. This process is repeated, adding a few inches of trunk each time. Some taper will result from this, but not a lot. You do get nice crooked trunks without sacrificing much growth. The wind blows that pots over anyhow if I don't prune them down.
By the time I get them in four inch pots I have some pretty nice looking plants suitable for shohin, but the leaves are really a little large for Shohin with the exception of perhaps M. sargentii or M. x zumi cvs. This takes only two to three years. Next they go into one gallon cans for more development. One inch trunks can be obtained in about three to four years from the original cutting. The trunks will have nice little crooks and bends in them, and the plants should be flowering regularly, with little fruits following.

Developing Trunk and Taper

It is difficult to get good taper on Crabs despite the fact that they are relatively fast growing. They always want to be cylinders, albeit fat cylinders as they get older. The way around this problem is to reduce the whips to within about 6 inches after letting them grow completely wild for 2 or 3 years. This can be in large containers or in the ground. The plant will respond by throwing many branches below the cut in all directions that eventually bend back upward. Let all these grow wild until winter. Then head them all back to within several inches of the trunk, but preserve a new leader from the top of the plant.
Repeat this process as long as you like. What happens is that the multitude of low branches will form an enormous lower trunk. These lower branches can be removed (they will be too large for bonsai ) when the tree is dug up and new scaffolding branches trained once it is placed in a smaller training pot. Trees in the ground will develop 4 to 6 inch trunks in 5 years with this method.
For an in depth discussion on growing larger trunks go to the article Developing Large Trunks for Bonsai.
Once potted for bonsai it is time for branch development. Branches should already be in place before potting except for possibly the small branches in the apex. I let them grow wild after potting up. After they begin to fill the pot, which only takes a few months, I cut back the long extensions that have grown on my selected branches and begin pinching them regularly to get nice close internodes the rest of the way out the branch. If a branch needs more caliper you can let it grow longer for a while. Branches in the top of the tree have to be watched very closely because most of the growth is directed there and they will soon be larger than the lower branches if you don't pinch them back regularly.
Most crabs will need repotting every year due to their fast growth rate. Larger bonsai may need it every other year or so. If they begin to push out of the pot or decline, it is time to repot. You can repot all season long if you are careful and an experienced bonsai enthusiast. Beginners should stick to spring and fall.
It is never possible to get very much ramification on crabs so don't worry about it, if you can get four or five sets of forked joints on a branch you will have a very nice tree. They can be defoliated in spring for smaller leaves and tighter internodes.

Pests and Diseases

Crown gall is sometimes a 'problem'. This is a parasite that makes warty nodules on the surface roots and crown of the plant. It seems to cause no adverse symptoms, and some of my trees have lived with it for years. The wonderful thing about it is that it creates spectacular nebari. I have one plant in training that has about a two inch trunk, but the gall covers about ten inches of root surface, which will nearly fill the pot when it is finished.
All sorts of bugs and critters love to eat apple leaves so you will have to deal with all of them, including deer. Snails and slugs put big holes in the leaves. Caterpillars of various sorts will roll up in the leaves. They are the first plant in the spring to get aphids. Mites will move from their favorite (Quince) to crabs when the pressure gets heavy. Woolly aphids are serious pests and hard to eradicate since they will live underground on the roots as well as the upper portions of the plant. They can be controlled with a good systemic insecticide.
Diseases are less of a problem, the most common being powdery mildew which is easily controlled with Funginex or simply giving them more sun and keeping the foliage dry at night. Cedar Apple Rust is a serious problem in many areas of the country. It can be mitigated by the use of fungicides and by keeping junipers out of the immediately vicinity of your apples.

Culture

Crabs are greedy little plants and require regular feeding and high calcium levels for lots of flowers and fruit. Stop the nitrogen in about August or September for better flowers. Regular, thorough watering is a must. They suffer little from root rot and can be placed in a somewhat denser soil mix to ease the watering requirement in summer. Full sun in most areas is best. In the very hottest, driest areas, full morning sun and afternoon shade may be necessary to keep them from drying out. They require a period of winter chill to set flowers, but this is easily obtained in most areas, other than perhaps the deep south.

Cultivars for Bonsai

The best cultivars for bonsai are the smaller leafed ones that develop some degree of taper on their own and are inclined to produce low twiggy branching no matter what the top of the tree is doing. These include 'Hopa', 'Hime Ringo', 'Mary Potter', sargentii and zumi cvs. Good plants for fruit are 'Snowdrift' which has a profusion of small yellow persistent fruit, and 'Sugar Tyme'. These are some of my favorites, but virtually any crab can be used.
A cultivar new to us is 'Louisa', a true weeper, the branches hang practically straight down. The buds are deep pink, opening to a beautiful true pink. The fruits are gold yellow with a blush of red and a little less than half an inch. It is a newer cultivar and very disease resistant. Father Fiala (Flowering Crabapples) proclaims it to be "An outstanding crabapple". I don't know if it will be possible to propagate it from cuttings, this will have to wait until next year. This one is quite exciting. The arc of the weeping branches is naturally about six to eight inches so that in a larger bonsai wiring the branches down would not even be necessary.
Another new cultivar for us this year is 'Weeping Candied Apple', it has reddish leaves and good red new growth with dark pink-purple flowers and small red fruit. It is an aggressive grower and very easy to propagate. It's weeping character will not be evident in bonsai, although it's branches could be wired down.
'Hime Ringo' has double light pink flowers, but there is some trouble with the name. I have not been able to trace the name or lineage to a species, and I am afraid that this is another example of Japanese naming by 'group' or 'type' rather than species. I have my doubts as to whether all the plants being sold in this country as 'Hime Ringo' are in fact the same cultivar. The clone we are producing is an excellent subject for bonsai. It produces many low angular branches with ease.
Really good red forms are 'Lizet' and 'Royalty'. Unfortunately both of these have been really difficult for me to propagate from cuttings. I may have to get this one from tissue culture.
The smallest leaf form that I have been able to find is M. sargentii. These have really small lobed leaves, almost like oak leaves. They reduce nicely to about an inch. The species grows to about ten feet and is very wide spreading rather than upright, it has tremendous bonsai potential. The buds are pink, opening to almost pure white. The cultivar M. s. 'Tina' is a superior selection that has very dark pink buds at the same time as other buds have opened to pure white flowers for a thrilling display of color in the spring. This should be one of the finest cultivars of all crabs for bonsai, although it will be rather slow growing.
'Sugar Tyme' has the most fantastic small fruit. They are red and persistant. Here they usually last until after the first of the new year. As the fruit ages, it takes on a reddish fluorescence that is an incredible sight on a cloudy day with the backdrop of dark wet branches. Not only that, but it sets fruit in huge clusters of fifty in a spur. I have taken several hundred fruit from a single small tree. It has pinkish white flowers in the spring, medium sized leaves and is not overly aggressive.

And finally

I recommend that any of the standard apples be considered for bonsai, although most will have to be used for three to four foot bonsai to make them work. I love the 'Moon through the branches' style where one apple is left on the small bonsai. In fact the sight of such a pear specimen many years ago was instrumental in my voyage toward bonsai from landscape work.