by Randy Davis 

Due to its length, this will be a two-part article. The second part will appear in the June newsletter - ED

Well, it is spring and the trees are beginning to leaf out, bringing with them the excitement of another bonsai season.  In our part of the country, 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 1 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 use as bonsai, they are not the only species that should be considered when selecting 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; and, for our purposes, we can leave it at that!

As I mentioned 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 specific maple species should consider leaf size and inter-node length characteristics first and make sure to match them to the style and size of the bonsai that you are intending to execute.  For the smaller bonsai, one should select those species which have excellent leaf reduction characteristics as well as short inter-nodes.  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 that 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 for early spring affect before the leaves emerge which will lengthen your bonsai experience to year round rather than just the summer months.

The design styles used for maples in my mind should represent how they appear in nature as a general guideline and can be found in the following forms;  Informal upright, Slanting, Literati, Natural, Double trunk, Multi-tree,  Forest, Root-over-Rock and Exposed Root.  For some reason, it has been my experience that 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 its 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 leaf reduce and shorten inter-node length of the species. Cultivar selection is also important in this, as there are many of them  and, of particular note, are the dwarf cultivars that will influence your selection.

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 advantages 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 inter-nodes 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. When confronted with this, 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 inter-node 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 flush spring growth has finished and you're heading into the early summer months.  In subsequent years, the trees will respond with the smaller leaves and inter-nodes, as the root system begins to be bound again by the container until its next repotting comes due.  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 3 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 that 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 during the spring flush of growth is when girdling of the branches will most often happen.  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.   Personally, I tend 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 since it still contains summer water.  Wiring at this time will enable you to place the branches in their new positions with less potential on breaking them.  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 hardens 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 at 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. However, look for ants, 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. It 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 3 times during the winter months will eliminate the problem. If you store your trees in an area that has protection from rain, then 1 spraying in the fall as you put them away, 1 in mid-winter, and the most important spraying, is 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.