Not All Maples Require the Same Leaf Management

I know that this article should wait until the spring when you can immediately put this information into practice but I’ve been watching video clips called the Bonsai Art of Japan with Owen Reich, Dmos by Ryan Neil and Bjorn Bjornholm.   From these I learned that it is important to trim your maples to allow light in to the trunk of the tree to encourage buds that will add to the ramification of your maples.  At our show in July 2012, Ken Huth mentioned that he removes the larger leaves on maples so that the tree develops more small ones.  When Linda and I were in Japan, we saw workers cutting the better part of maple leaves off, leaving a small portion of the leaf and petiole.  I assumed this was to allow light in.  This cutting allows inner buds to develop and prevents branch dieback.  It also improves air circulation and prevents mildew.  (It did seem humid in Omiya Village.) I recently learned  from these videos that Japanese maples and Trident maples require different techniques of leaf management.  And within the group that we call Japanese maples, the cultivars of Shishigashira require slightly different care.  Owen and Ryan noted it in their videos; Ryan’s was a critique of the Midwest Bonsai show in Chicago.  A great deal has been written about the care of maple bonsai.  This article only presents leaf management.  There is an article on Trident maple care on our club website.  They are also candidates for air layering and trunk chop.

As with all maples, Japanese maple (Acer palmatum) leaves grow in pairs.  One leaf in each pair should be removed.  Use sharp scissors to cut the stem holding the leaf in half.  This method does not weaken the tree like total defoliation does.  Ryan Neil said you should never defoliate a tree as it weakens them too much.  Leaf removal should be confined to the leaves growing on the outer edges of the foliage mass, not the leaves growing in the interior of the tree.  If removing a single leaf of a pair does not allow the light to reach the interior, then half of the remaining leaf may need to be removed with sharp scissors.  Fold these leaves in half along the vein in the middle and cut at an angle, the results should look more like a normal maple leaf.  Special scissors are sold for just this purpose. This pruning of Japanese Maples is usually done sometime in May, depending on how early the buds opened in the spring.  Remember that you will get die back if you prune at the wrong time and you will get die back to the first healthy bud behind where you cut.  Ryan Neil also stated that he is a big fan of cut paste use on maples to prevent die back from moisture loss.  It also prevents fungus from developing at the wound.  When you select the leaf from the pair and remove it, your next bud and hence the direction of branch growth will be on the side with the leaf as the leaf is feeding the bud at its base.

Shishigashira Japanese maples actually consist of two cultivars, Acer palmatum 'Mejishi' and Acer palmatum 'Ojishi', whose names are based on the mythological female and male lions in Japanese drama.  Shishigashira Maples have the typical paired leaf growth pattern; however, their internode lengths are shorter than other Japanese maple cultivars.  If the branches are not properly trimmed they will develop unsightly bulbous branch tips.  So cut the branch tips back to the second set of leaves rather than the first set as recommended for other Acer palmatum cultivars.  Use tweezers to pinch off the first set of leaves so that only the second set of leaves remain.  It is not necessary to remove one of the leaves from the pair, or to cut individual leaves in half as Shirigashira leaves are naturally smaller.  The small leaves and limited availability usually mean that these cultivars are quite expensive.

Acer buergerianum (Trident maples) leaves harden off in late April through May.  The new elongated growth should be trimmed back to the first pair of leaves, unless you’re developing length in that area.  From late May until July, depending on the weather, you can defoliate a healthy Trident maple. Defoliation can very from complete, to outer canopy, or individual branches. Leaves are removed by cutting the petioles in half.  Though plucking them all off with your fingers reportedly doesn’t hurt the tree.  (We did not see the finger plucking method used in Japan.) This defoliation and pruning allows light and air in to the inner buds and creates shorter nodes and smaller new leaves.  I understand that there is a fine science to the timing, so that the new leaves will be in place by our show in July.  New leaves reportedly sprout in 2-3 weeks; this means the end of June should work this year.  If it is rainy after your new leaves sprout, watch for fungus.  While it wasn’t mentioned, I suspect that the same direction of growth by leaving a leaf on would occur with Trident maples as for Japanese maples.  It was mentioned that complete defoliation should only be done once in any year, and not in consecutive years on the same tree to allow it to rebuild its energy. 

Do not remove leaves on any maple varieties once it gets really hot, in 2012 this was late June or July, as it may cause dieback.  Failure to cut new growth back to one set of new leaves will result in longer internode distances, less ramification and less taper in the branches or trunk.  Healthy properly fertilized maples may need to be trimmed as described three or four times each growing season to maximize ramification and refinement.  

Above article found on ColumbusBonsai.org