Part 22 of a series by Eugene Howell
This is a continuation of an article on bonsai leaf reduction by defoliating. In the previous article we learned that if a bonsai loses all its leaves during the growing season, it will replace them with new ones, but that the new leaves will be smaller than the original ones. Thus we have one technique for reducing leaf size; complete defoliation of the tree.
When the leaves are removed the tree maintains life by using its stored food, so completely defoliating a tree too frequently is not recommended unless you happen to live in a subtropical area like South Florida. In temperate parts of the country it’s recommended that defoliating a bonsai be done only once each year because the tree must be given enough time (with leaves) to store up food to get through the winter. In Florida our evergreen trees do not go completely dormant and deciduous trees are dormant for only a few weeks. So a large store of food isn’t necessary. Thus, here in Florida defoliating bonsai can be done in late Spring, and again in late Summer.
Although some bonsai hobbyists defoliate by plucking the leaves from the plant (by far the fastest way to do it), if you want the most number of leaves to grow back, you should use bonsai scissors and cut each leaf stem. When the leaves are plucked, many of the buds at the bases of the petioles are damaged and do not develop into a new leaf. When the petioles are cut with scissors, the dormant buds are not damaged and a maximum number of leaves are replaced with new, smaller ones.
The next method of bonsai leaf reduction is a good bit less labor intensive than the one just described. In this second method we once again take advantage of our knowledge of botany.
From the discussion in the first part of the previous article you know that the meristem cells at the tip of a small branch are dominant. When the tip of the branch is removed the dormant buds come out of their dormancy. A second thing that happens as a result of cutting of the branch tip, is that the leaves remaining on the branch will stop growing in size and will remain the size they were at the time the branch tip was removed. This means that you halt the growth of each leaf on a bonsai at just about any size you wish. The trick, however, is to examine the tree often enough to stop each leaf before it grows too large, and this is tough to do because it requires daily, detailed observation. If, like most bonsai enthusiasts, you have several bonsai trees, this task could be very time consuming.
However, there’s a catch to this process. We’ve halted the growth and size of the leaves by removing the dominant meristem cells after cutting off the branch tip, but once removed, dormant buds further down the branch come out of dormancy and some begin to develop into new branches, thus reestablishing new dominant meristem cells. As the new branches grow, any leaves further down the old branch will have a tendency to start growing again in size as the new branch grows. So what do you do about this? You must do the same thing, branch tip removal, before the leaves on the older branches get too large. So you can easily see why this requires such close observation on a daily basis.
The third method of leaf reduction is the easiest of all. First you pinch the tip of each branch and then simply cut off the largest leaves and keep the smaller ones. As new leaves grow, continue doing the same thing. This cycle never ends, but after a few weeks the tree will be covered with smaller leaves and any that get too large will be readily apparent. To make this technique successful you obviously must be observant and look carefully at your bonsai each day. What you don’t want to do is ignore the tree after having spent so much time developing smaller leaves. If you did, then when you finally get around to inspecting it you’ll find that, once again, it’s covered with large leaves.
There are three good methods of accomplishing leaf reduction on your bonsai. One is labor intensive but does not require constant vigilance, one requires much less labor, but does require daily inspection, and the final one requires only moderate labor and attention. Of these three methods, you’re likely to find one that works best for you.
Photo credit: flickr Creative Commons, My Bonsai Tree by Qorize