Maple (Acer) Theory

Being as this is the perfect time to begin applying certain necessary techniques to Maples (Japanese, Trident, and Shishigashira in particular), I thought I’d take the opportunity to post an abridged version of my previously published articles regarding the subject (ABS Journal and Bonsai Actual Spain).

Late Spring/Early Summer Trimming
           This is perhaps the most important section of this article as the following techniques are of complete necessity, though little known or at least little practiced outside of Japan.  In the bonsai community, when one is asked what the most important feature of a bonsai is, the typical response usually involves some stylistic element, i.e. trunk movement, surface roots (nebari), etc.  Although these components are important to bonsai design, they are not the most important feature of a bonsai.
What is then?  The answer lies deeper within the branches, literally – the inner buds and branches, those found beneath the outer layer of foliage, those closest to the trunk.  Without these inner branches there will be nothing to cut back to, creating long-term problems, as the bonsai will simply grow larger and larger until there is no choice but to plant it in the landscape.  Of course there are numerous grafting techniques for artificially creating back buds, but why make unnecessary work for one’s self?  It is much more beneficial and less time consuming to take a preventative stance rather than a reactionary one.  The cause of inner bud and branch dieback is, more often than not, lack of proper light and air circulation in these areas.  The following techniques, if implemented at the correct time in late spring/early summer, can prevent this unnecessary dieback.

Japanese Maples
As mentioned previously (in the unabridged version), Japanese Maples, Acer palmatum, have an opposite growth pattern.  As the leaves harden in May, one leaf in each pair should be removed to allow light and air to the inner branches of the tree.  Use sharp scissors to cut the stem holding the leaf in half.  This is not a form of defoliation (in its usual sense) as removing only one leaf per pair will not induce a second flush of growth in those areas during the same season.  Therefore, this technique presents absolutely NO health risks (i.e. weakening of branches or dieback) to Japanese Maples.  It should also be noted that this single-leaf removal technique should only be applied to the outer foliage mass, leaving the inner, weaker pairs of leaves untouched.

If, for some reason, the removal of one leaf per pair does not allow sufficient light and air to reach the inner portions of the tree, the remaining single maple leaves themselves should be cut in half.  Grab the individual leaf in one hand, lightly folding it along its central axis of symmetry.  Use sharp scissors, making a swift, angled cut.  When the leaf is released, it will unfold and still appear to have a rounded, Japanese Maple leaf shape.  If it is cut perpendicularly rather than angularly, the leaf will have an unnatural, box-like shape.  Again, this technique will in no way weaken Japanese Maple bonsai and should be performed sometime in May, optimally speaking.

Trident Maples
Trident Maples are trimmed rather differently than Acer palmatum.  As the leaves harden off in late April through May, elongated shoots should be trimmed back to the first pair of leaves using scissors.  In late May through July (depending on one’s geographic location), defoliation should be performed, in many cases more than once per tree per growing season.  This, in contrast to the previously mentioned techniques for Japanese Maples, can potentially weaken the tree, so only perform defoliation on healthy plant material.
There are several approaches to defoliating Trident Maple bonsai – complete defoliation, individual branch defoliation, partial outer canopy defoliation, etc.  The least detrimental, and in fact most beneficial, approach is the latter – partial outer canopy defoliation.  This particular method involves removing the outer layer of foliage while leaving the inner, more delicate leaves untouched.  This not only allows light and air to the inner buds, but it also creates smaller secondary growth and shorter nodes, which aids in quicker overall ramification of branches.

This defoliation technique can be performed either with sharp scissors or, more efficiently, with fingertips.  If using scissors, as with Japanese Maples, cut the leaf stems in half.  When using the finger method, simply grab the leaves with the padded fingertips and gently pull away the outer foliage layer.  This will often completely remove the stems from their bases but does not harm the tree whatsoever.  Again, only perform this technique on healthy material.
If done properly, a new set of smaller leaves will emerge within two to three weeks.  Once those have hardened off, depending on the health of the tree, this technique can be performed again and up to five times in a single growing season.  As a general rule, the older the tree, the less times per single growing season should this technique be employed.  Partial defoliation really is a necessity in maintaining the health of back buds and inner branches, so please do not be afraid to apply it to your personal Trident Maple bonsai.  Be forewarned, however, that if defoliation is performed during the rainy season, one must watch closely and spray for fungus as the new leaves are highly susceptible to rot and other such problems.

Shishigashira Maples 
Shishigashira Maples are unique, both in growth habits and the trimming techniques necessary for their maintenance.  Like all maples, Shishigashira have the trademark opposite leave growth pattern; however, the node length between each pair of leaves is considerably shorter than most.  In fact, the nodes are so short that if not properly trimmed, Shishigashira Maples develop unsightly, bulbous branch tips.  In order to prevent such a problem, a specialized and extremely time-consuming trimming technique must be employed.
After the leaves have hardened in May, cut back to the second pair of leaves rather than to the first as with standard Acer palmatum.  Use tweezers to pinch off the first pair of leaves on the entire tree.  By allowing only the second pair of leaves to remain, this slightly extends the shoots and thus prevents the bunching of branches caused by nodes that are too short.  Because the leaves on Shishigashira maples are already relatively small, it should not be necessary to remove one in each pair, nor to cut individual leaves in half.  Sufficient light should naturally enter the depths of the inner branches.

In Closing
            The techniques and practices mentioned above are necessary in developing and maintaining healthy, beautiful maple bonsai.  Please keep in mind that the timing of the trimming techniques will vary depending on one’s geographic location and the climate found therein.  In addition, the timeframes mentioned above are general guidelines for optimal results.  If one waits until June or even into July, it is still okay to perform leaf removal or leaf cutting; however, the later one procrastinates, the more likely the inner buds and branches will weaken or dieback.
Although these techniques are somewhat tedious and time-consuming, they are necessary for the long-term health and maintenance of maple bonsai.  These very basics are the building blocks in the foundation of bonsai understanding and will ultimately aid in the future progression and development of the art as a whole.  I encourage you to apply the above-mentioned techniques to your personal maple bonsai, and I guarantee the long-term results will be well worth the time and effort.