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Maples for Bonsai
American Bonsai Society
Maples for bonsai
By Randy Davis
Well, it is spring and the trees are beginning to leaf out, bringing with them the excitement of another bonsai season. One of the very first trees to leaf out is the Red Maple (Acer rubrum) which made me think it’s time to finally do an article on Maples that are used for bonsai. I say “finally” because the Maple family is so huge, with approximately 150 species, it has been plaguing me on how to formulate an article without making it confusing. Of course, when one looks at the number of Maple species that are used for bonsai by American artists they can be counted on one hand and, even then you wouldn’t have to use all of your fingers. American bonsai is almost exclusively limited to the Trident (Acer burgerianum), Japanese (Acer palmatum) and Amur (Acer ginnala) maples. While these three species are all excellent for bonsai they are not the only species that should be considered when selecting deciduous plant material. Maples present some problems to the average enthusiast due to the huge number of species and even the variability within the cultivars of a single species to select the right one for the correct application. Let me explain a little, I knew this was going to be difficult but here we go anyway. We’re all familiar with the horticultural terms of “Genus,” “species” and “cultivar”. If you’re not familiar, here’s an example - Acer palmatum “Arakawa” – “Acer” is the Genus, “palmatum” is the species and “Arakawa” is the cultivar. From a taxonomic level what makes the maple family difficult is that it also includes terms such as “Series,” which is used to group similar species together such as the “Palmata” series which includes Acer palmatum and Acer japonicum and others which are closely related; and “sub-species” such as Acer palmatum ssp: (subspecies) amoenum and ssp: matsumurae which are very closely related but not sufficiently different to warrant their own species classification. Suffice it to say, the maples are confusing. For our purposes we can leave it at that!
As I mention earlier, the Maple family is extremely large some 150 species and when one considers cultivars variability abounds for the bonsai enthusiast to choose from. The species are distributed fairly evenly around the world. I have included below a list of the species that are and should be considered for use as bonsai. Those identified with an “*” have been used as bonsai and while not often seen, there are excellent examples of them. The others are species that while difficult to find should be tried as they do have excellent characteristics that can be used to full advantage as bonsai.
More important to the bonsai enthusiast, the selection of a maple species should include consideration leaf size and internode length characteristics first. This will allow you to match them to the style and size of the bonsai that you intend to execute. For the smaller bonsai one should select those species which have excellent leaf-reduction characteristics as well as short internodes. For larger bonsai there is much more flexibility in species selection. Another consideration is that some species such as Shantung maple (Acer truncatum) which have horrible leaf size and large internodes which normally would not be selected for use as a bonsai can be made into bonsai for winter viewing to enjoy the spectacular furrowed white bark. Individual species features such as flowers can also be taken advantage of in early spring before the leaves emerge. These can lengthen your bonsai experience to year round rather than just the spring and summer months.
The design styles used for maples, in my mind, should represent how they appear in nature as a general guideline. These can be found in the following forms; informal upright, slanting, literati, natural, double-trunk, multi-tree, forest, root-over-rock, exposed root and windswept. For some reason, almost all bonsai Maples that I have seen in shows over the years are represented as “perfect” trees or groupings. What I mean by “perfect” is that the artists have neglected to use features such as jin or shari which are so common in maples in nature. When one is designing a tree of age and you have the luxury of having a tree with a large trunk with character, the lack of these design features is in my mind a sinful mistake. The lack of use of jin is reasonably understandable in that the dead wood of maple is soft and will rot off in a number of years but that should not inhibit one from using it as a purposeful design feature. Use of wood preservatives can greatly extend the life of jins on a tree. Shari should be used as it is one of the more commonly seen attributes of an ancient tree in nature. Maples by their nature are surface rooted trees and don’t go deeply into the ground but rather spread out on the surface of the ground and develop vigorous feeder root systems. It is for this reason that a good Maple bonsai will always have nebari as a prominent feature in their design. While difficult to develop on a young tree, nebari can be enhanced with early attention to their development during repotting. The larger roots which are close to the surface of the soil will grow in girth faster when they are exposed to sunlight. Take the time to enhance your tree with these simple features that will add character and individuality to your Maple bonsai.
We’ve all heard the term “size is important.” In Maple bonsai it is extremely important! When you’re thinking about working with maples it is essential to have an understanding of the characteristics of the species and match that appropriately to the size of the finished bonsai. This is important when you’re out at a nursery, a bonsai show or in the woods selecting a tree. We can make this a relatively easy task by organizing the species into groups for appropriate use as either small, medium or large bonsai. The driving force in this grouping is the ability to reduce leaf size and shorten internode length of the species. Of particular note are the dwarf cultivars that will influence your selection.
Small bonsai – (Under 12 inches in total height)
burgerianum campestre ginnala monspessulanum palmatum
Medium bonsai – (13 to 24 inches in total height)
burgerianum campestre carpinifolium
cercinatum cissifolium ginnala
Japonicum monspessulanum oliverianum
palmatum rubrum truncatum
Large bonsai (25 to 48 inches in total height)
burgerianum campestre carpinifolium cercinatum cissifolium davidii ginnala japonicum monspessulanum
palmatum pennsylvanicum pseudoplatanus rubrum saccharum truncatum
All of the maples are vigorous growing trees both in canopy as well as the root systems and as such are well suited to the constant pruning put on them as bonsai subjects. Pruning of the tops can be aggressive as maples have what seems a limitless abundance of dormant buds which is advantageous for both canopy ramification of the semi-finished bonsai as well as ground-grown trunk stock. In general, leaf reduction is accomplished by constant pruning of container grown material as well as the occasional leaf pruning technique. The experienced grower knows however, that the repotting and root pruning of a maple will often result in large ungainly leaves and longer than normal internodes that immediately follow in the spring. This is the result of vigorous root growth once a tree is root pruned and is just one of those things that must be dealt with on a regular basis. The remedy is to provide adequate direct sunlight to limit the leaf size and strong pinching of the new growth back to the first set of leaves to force smaller internode growth. Another helpful technique done in combination with pinching and sunlight is to limit the amount of available fertilizer to newly repotted trees until the spring flush of growth has finished and you’re heading into the early summer months. In subsequent years the trees will respond with the smaller leaves and internodes as the root system begins to be bound again by the container until its next repotting. Trees which are in good health at the time of repotting can withstand aggressive root pruning to encourage feeder roots rather than the large structural roots which for the most part are not necessary in bonsai other than for the design aspects of good nebari formation.
The cultural aspects of maples are relatively easy but there are a few things that should be addressed to keep them in good physical shape. Watering in general is not a large concern other than making sure that they don’t get overly dry. Most maples love water and fertilizer and will respond to them quite well. Many of the American native species are often found in the lower wetlands and will take flooding for moderate periods of time. Some, on the other hand, like Acer monspessulanum, are found on the drier slopes of southern Europe and are better off with better water regulation. If you find yourself in a situation where you have a tree that has dried out and the leaves have become significantly desiccated immediate action should be taken in the form of drenching the soil in a bucket of water and then placing the tree in a protected shady position. Most maples will respond by putting out a fresh set of leaves in about three weeks. In addition it is wise to eliminate fertilizer on trees that are in a recovery mode as well.
Wiring of maples is one of the things the artist should take very seriously. While wiring can be done at anytime of the year on older mature wood, at least one season old, you should keep in mind that the spring flush of growth is when girdling and scarring of the branches will most often occur. Maples, as with other fast growing deciduous trees, put out all of their trunk and branch girth from early spring until Mid-summer. If you wire at this time of the year keeping an eye on your trees is essential. I prefer to wire Maples at the end of fall just as the trees begin to take on their fall coloration. The new growth has matured and older wood is still pliable as it still contains summer water. Wiring at this time will enable you to place the branches in their new positions with less potential for damage. This timing is important, most deciduous trees at the onset of the colder fall weather begin to expel water from their branches to brace themselves for the cold winter extremes. It is this natural process that you want to take advantage of which will harden the newly wired branch into place over the winter months.
The types and number of pests and diseases will greatly depend upon your location and the spraying program that you have established for your trees. In general, the pests most commonly seen are Mites, Aphids, and Scale. Mites and Aphids can be controlled with commonly available insecticidal sprays using the recommended methods that come with the product. For those who don’t like to use insecticidal sprays these pests can be kept under reasonable control by using a strong spray of water late in the day just before dark. Aphids tend to locate themselves on the soft new growth. Mites tend to be on the underside of the leaves at the leaf veins. Scale can appear both during the summer and winter months and appear at branch junctions and are sometimes difficult to notice but look for ant’s as they tend to appear on trees at the same time as scale to gather the dew that the scale produce. The best recommendation that can be made is to develop a relationship with your local Department of Agriculture or Entomology agents to get familiar with the pests in your particular area.
Japanese Maples (Acer palmatum) are extremely sensitive to verticillium wilt for which there is no control other than cutting out the affected branches well below the affected area to healthy wood. It is extremely important to remember to sterilize your tools between cuts. The most effective control for verticillium wilt is the control of the soil you use as it is where the verticillium spores live. Taking measures to sterilize your soil or ensure that it does not become infected will go a long way to help make sure you are not plagued with this devastating disease.
Anthracnose can be effectively controlled with a chemical mixture of hydrated lime, copper sulfate, and water, known as Bordeaux mixture. This is registered for use against anthracnose on Maple and Elm. Anthracnose is encouraged by wet spring weather as the tree begins to leaf out. Spraying at least three times during the winter months will eliminate the problem. If you store your trees in an area that has protection from rain, then one spraying in the fall as you put them away, one in mid-winter, and the most important spraying when you see the buds begin to swell in the spring will be sufficient. If your trees get rain during the winter months it is wise to add a few extra sprayings after heavy rainfall. Good air circulation in your growing area will also greatly help.
burgerianum (Trident maple) – The trident maple is one of the stalwart maples for bonsai. It has been used for many years and conforms to all of the needed requirements to make an outstanding specimen or group bonsai. It is easily found at bonsai shows and getting more available in the commercial nursery trade. When trees grown are from seed they will usually conform to one of two types. Type I is a tree with smaller leaves and very good internode length that is the preferred form for the smaller bonsai, under 12 inches. Type II is a tree with somewhat larger leaves and longer internodes with a flaking bark that forms on younger trees. The buds form on the branches in an alternating pattern with one set of buds in the horizontal position on the branch and then the next pair of buds will form in the vertical position. You can use this to your advantage when you are pruning for shape. There a number of cultivars including a variegated leaf form.
campestre (English Hedge Maple) – Not often found in the American bonsai community, this is used extensively in Europe. This is an excellent bonsai subject with very deeply lobed leaves apple green in color. Hedge maple has the habit of longer internodes than one would like but with diligent pinching it can be kept under control. It is a fast growing tree and will form a very nice crinkled bark rather quickly on a tree at five years or so. If you enjoy working with maples this would be a fine addition to your collection. Acer campestre is somewhat difficult to find but well worth looking for at bonsai shows.
carpinifolium (Hornbeam Maple) – This species is not often found in bonsai outside of its native Japan but will make a wonderful larger-size bonsai. The leaves are oval in shape and have deep veins making it very reminiscent of Hornbeam (Carpinus). The internodes are large and the wood is very straight grained which is the reason it will not perform well for bonsai under 18 inches or so. The leaves are vivid green during the growing season without any significant coloration in the fall other than the typical yellow and brown.
cercinatum (Vine Maple) – The vine maple is used for bonsai far more on the West coast of the United States, in particular in the North West where it is native to the woodlands of Oregon and Washington state. To the untrained eye it is often mistaken for Acer japonicum because of the similar leaf structure. It is differentiated from japonicum by its very long inter-nodes which are very long with branches often weeping to the ground from which its common name is derived. Leaf reduction is moderate but because of its long inter-nodes it is better suited to the larger size of bonsai. The leaves are apple green in color during the summer months becoming a lovely butter yellow in the fall.
cissifolium - One of the only trifoliate maples that will work well for bonsai due to good leaf reduction characteristics not found in our American native Acer negundo. Native to the mountain forests from southern Hokkiado to central Kyushu in Japan. The internodes are moderate and can be controlled well with adequate pinching. The leaves will maintain a very small size in bonsai culture for a trifoliate maple. The emerging leaves are pinkish red in color in the early spring and the bark is a light cinnamon color making for a lovely display. Rather difficult to find but if you’ve ever been enticed to try a trifoliate maple this is the one to use. No fall coloration.
davidii (David’s Maple) – David’s maple is a native of central and western China. The leaves are generally oval (lanceolate) in shape five to six inches in length and will reduce moderately. The leaves are a rich dark green with the leaf petiole and leaf veins red in coloration making for a very nice contrast. A small multi-trunked, this is a natural for the double or triple-trunk design of bonsai. The most interesting part of this tree is the striped bark. Even from a young age the bark is dark green with pinkish striping and when mature it is dark green with white stripes. This is one of those trees that would make a wonderful winter-viewing bonsai because of the unique bark. It is one of those trees that you should start out as a young tree for development and avoid trunk chopping.
ginnala (Amur Maple) – This is one of the more commonly used Maples for bonsai. It has excellent leaf reduction and inter-node characteristics. The leaves are three to five inches with three lobes and serrated leaf edges. Leaves are a nice rich green and are often spotted with small pink spots in early spring. The bark of older, established trees is a wonderful bright grey coloration. They can be field grown, trunk chopped and then grown out to large caliper trunks in five to seven years. They are impervious to root pruning. Amur Maple is very cold tolerant making them excellent candidates for the northern climates with little or no winter protection needed.
japonicum (Full Moon Maple) – I only include this tree in the list because it is one of the favorite trees of people who collect Maples. The leaves are round five to seven inches in diameter with seven to nine lobes of an apple green color. There are upwards of 75 cultivars known of which only a handful are available through the specialist nurseries. The internodes are rather large as well as the dormant buds of this tree. While I have seen some small examples (under 12 inches) as a bonsai they are often without much visual interest. This is one of those trees that would be far better suited to bonsai in the larger format. Cultivars are often grafted so care should be taken in selecting a tree for bonsai that has a low cleft graft so it is not quite so noticeable.
monspessulanum (Montpellier Maple) – A small shrub type maple native to southern Europe. Not often seen in the United States other than in horticultural collections of university’s or enthusiasts. This tree has a small three to five inch leaf that is three lobed with a smooth edge. It leaf reduces quite nicely. Internodes are moderate in length but the branches seem to be quite stiff and straight so frequent pinching is required to make them into nice bonsai. The bark of the tree is nicely furrowed with age adding to its visual interest as a single tree specimen. The tree is fairly difficult to find but worth it as a welcome addition to your broadleaf tree collection. Propagated exclusively by seed of which only 10 percent are viable.
palmatum (Japanese Maple) - The Japanese maple has been in formal cultivation in Japan since the 17th and 18th centuries. For bonsai, it makes sense that its use has also been long and fruitful. Over the years there have been many hundreds of cultivars developed, many still in cultivation and many that have probably been lost. From a care perspective, treatment of the cultivars is the same as the species with the exception of pruning. The dwarf forms requiring little to no pruning (other than design considerations) at all because of their short internodes. The bark of the species when young is bright green and turns to a beautiful grey with age. The cultivars may vary from the normal green bark when young to brilliant red as is the case with Sango Kaku, or dark purple with those in the Bloodgood (ssp: amoenum) group which will all turn the typical grey with age. Leaf size will also differ between the sub-species (a smaller leaf) for the palmatum group (ssp: palmatum) and the Bloodgood group (usually larger by half) which will have an impact on the size of the bonsai to keep it in perspective. Because of the number of variables in this species it is an excellent choice for bonsai and will provide the enthusiast much to consider in selection and use. Of particular interest is the cultivar “arakawa” which has a wonderful cork bark which is so unusual in the Maple family.
pennsylvanicum (Striped Maple) - An American tree native to the east coast from the north facing slopes of the Appalachians north to Nova Scotia and west to Minnesota. Pennsylvanicum is a tree with good potential as a larger bonsai specimen at 24 inches and larger. Leaves are three lobed and rather large at six to eight inches, but can be reduced by half with good growing and pinching techniques. The tree is one of the few “snake-bark” forms with conspicuously striped branches and trunks with wide white stripes. This tree should be used as a winter-interest tree as the bark will turn reddish with wide, distinctive white stripes. As with the other trees used for this purpose, trunk chopping should be avoided. For those interested in collected trees it is usually found as an understory tree and frequently found with A. saccharanum and A. rubrum in their native habitats.
pseudoplatanus (Sycamore Maple) - This tree is used far more in Europe for bonsai because it is native to that part of the world. The leaves are medium in size five to seven inches with three to five sharp-pointed lobes reminiscent of our native American Sycamore. I have seen some smaller examples of the tree in bonsai but in my opinion would be much better suited to the larger size of bonsai not less than 24 inches. Bark will peel in small scales with fissuring in large vertical strips on the trunk.
rubrum (Red Maple) – This is the predominant maple in the Mid-Western United States and not used for bonsai nearly enough. Leaves are three to five lobed and four to six inches on a mature tree but are very good at reducing to three to four inches or smaller under bonsai cultivation. Internodes will vary from large on a vigorous new shoot to very small on a tightly ramified branch. Vigorous pinching is required to maintain good branch structure on a smaller tree. I think that a tree in the 24-36 inch range is optimum for this species. This tree is dioecious meaning that there are male and female trees of which the males are better for use as bonsai. The male trees are vigorous growers where as the females are rather spindly and weak. Red Maple will not only make a wonderful tree during the summer months with bright green leaves but will also put on a lovely display of fall coloration in the yellow to red-orange range. From my perspective, the best time for this tree is the early spring when it puts on a wonderful flower display of bright red flower bundles before the leaves emerge.
Saccharum (Sugar Maple) – This is another American native tree that should be used for bonsai far more than it is. It is best suited as a medium to large size bonsai and will reward its owner with that lovely fall coloration for which it is so well known. The leaves are three to five lobed and four to six inches in size and will reduce moderately. Internodes are rather straight and should be pinched often to give the tree a more interesting looking format. The wood is also very tight grained and hard which requires mid-fall wiring otherwise they are known to break readily.
tuncatum (Shantung Maple) – This tree is a native of China and fairly difficult to find but well worth the effort. While the leaves are rather large on this tree with some pruning they can be reduced to an acceptable level. The leaves are five lobed and four to six inches across and can be reduced to half their normal size. In the early spring the leaves emerge a bright apple green with a purple cast over the leaf edges and leaf veins making for a lovely sight. The largest problem with this tree is the inter-node length, so pinching on a regular basis is required. As a medium size bonsai in the 16-24 inch size it will make a wonderful tree. The bark of this tree is its best asset and will give you many wonderful hours of winter enjoyment. The bark is very rough and fissured, more so than any of the other maple species and is a lovely white-cinnamon coloration. With the bark coloration and fissuring, from a distance it looks as though it is white with black stripes and really catches your eye. Well worth the effort if you can find it.