When to Take Off Japanese Maple Leaves in the Fall?
This is a tangly question…there’s what’s best for the tree, and there’s what we might want to do because fall leaves are rather nice looking.
For Japanese Maple, the fall color is often the most eye-catching thing in the yard. We want to see it for a while. But, if we wait until the leaves dry and fall off, we won’t be able to do any fall canopy pruning. The reason is that the tree will bleed for a long time if we cut after the leaves have fallen off naturally. For most Japanese Maples the window of time after leaf fall that you can safely prune is less than a week, much less than the 10 days often reported.
There’s two solutions to this…take the leaves off when at the height of color or just after, and do a careful fall shoot shortening immediately, or wait until spring to do this pruning. The first option shortens the time you get to see your tree in full color, the second will offer a possibly rougher looking tree during the winter silhouette time. Maybe the solution is ask yourself if you’re a color person or a shape person…either way, it’s a decision partly based on the tree’s needs, partly based on bonsai technique, and partly on personal preference. (And if you like to keep a tidy yard, pulling leaves off a tad early will greatly reduce picking up leaves off the ground).
One final point. If leaves are taken off while they are still green the tree loses resources. In the fall the chlorophyll is broken down to salvage amino acids and nitrogen, which is then brought back into the tree before leaf abscission. This helps strengthen the tree though the winter. (Anyone still convinced of the 0-10-10 fertilizer regimen in the fall for temperate trees should give this a long think…)
17 Comments
Beautiful! Any chance of before and after leaf removal shots?
Will take a few-
Are we saying that we should do our pruning before the tree has gone fully dormant? I was under the impression that it was best to wait for the tree to be dormant before doing any pruning. As for leaves I’ve been taking them off only after they are ready to come off on their own. That is to say that I give the leaf a little tug, and if it hangs on it’s not ready to come off.
That’s about right. If the leaf comes off without much persuasion, that’s a good time. Japanese maple is different from other trees in that they bleed if cut too late, this is not true of Trident maple, however. And most other deciduous trees.
In general the bigger the cut, the more we would want to do it while the tree is active. Even during the growing season. That way the tree can heal fast, rather than wait for months to do that, and likely die back a bit in the process. This is a rather large topic, really!
Michael, wonderful insights! I wish you would say more about this subject, as you opened up so many questions in my mind — about fall fertilizer, timing of leaf removal, ways to defoliate, etc. Please expand!
Best.
Felix
Unfortunately I’ve opened a pandora’s box, doesn’t it seem when we make one statement it’s connected to a thousand others? The bugbear of blogging..
Well, it’s fun to talk about Japanese maple as it’s different from most other deciduous. A Trident maple, for instance, may be trimmed all winter long.
As for cutting off a green leaf, if we do that during the growing season, like in June, then we’re expecting some sort of response in the plant to recover the sugar loss. It regrows. Hopefully that regrowth is of some benefit we’re after, more twigs, thinner twigs, something. If we cut off a green leaf very late, like in October, then the tree has no time to respond and the nutrients in the leaf are then wasted. Wait a bit longer when the leaf has color and then we waste less and still achieve our fall goals of shape maintenance.
Hope that clarifies a bit-
MIchael, thanks for another great and timely post!
Does this also apply to tridents?
Tridents, and most other deciduous, are different in that they don’t tend to bleed much or at all from a cut in the dormant season. (On any tree, if you see a lot of bleeding, do a light repot and it will stop).
I saw the resemblance instantly. You will do well with age.
Without potassium no transport of amino acids and nitrogen in your tree.So how about fertilizing 0-10-10 at the right time?
The point I meant to make is that continuing with a balanced fertilizer, the same as we use during the growing season, is best for the fall as well. It may have use on trees for blooming, etc, which is what it was originally designed for. But not much need for it on bonsai in temperate regions.
Thanks, Michael! Very helpful! Could you please elaborate on the mechanism behind your recommendation not to take off leaves while they are still green?
I tried to with my response to Felix’s question-
Hi. Would there be any particular reason (besides personal preference in esthetics or preparing for a fall or winter show) why fall (shoot)pruning would be better for a tree (that’s allready good develeppod) than a pruning in lets say january? I personally cannot say that this is the case. Even when (shoot)pruning a little late in february, some bleeding off the tops of tiny shoots does not really harm the tree nor the shoots (if winter protection is ok), unless we would be talking about very small trees perhaps. Trees like the one on your picture are good developed and allready produce shoots with short internodes for the first couple of centimeter. So am I wrong to say that this shootpruning in fall is not really a technique for developement of such a developed tree? Even trees in development do not really benefit from that, rather on the contrary since they don’t yet need refinement. But, I understand you were mainly talking about esthetics, like you said ‘do you prefer colour or do you not mind a bit of a rougher look in wintertime. Rough, as in ‘the canopy pruning of small shoots’ just has to wait a bit but can be carried out at other moments, for development
If the bleeding is minor then there is maybe no problem. But consider that bleeding is sugar loss, you can taste the sap and it’s like maple syrup. If we trim too much, or worse do actual pruning and lose a lot of sap, the tree could be weakened. Could. That is my only point. Bonsai are small. I had to do quite a bit of small cuts on that Japanese maple featured. The tips get very strong even on a developed Japanese maple, and they must be cut to a thinner twig. That cutting alone can bleed quite a bit of sap. But yes, a tree as developed as this does need this trimming or it will soon become rank, although it could be done in early spring just as well, and an undeveloped tree you would not want to do this refined cutting on as you want the strong tip buds to develop the tree…two very different techniques, as you suggest. I’m not sure I’m answering your question, though-
HI Michael,
I second Felix’s request to expand! A specific question. You say that if we wait til the leaves fall off naturally the tree will bleed for a long time. I’ve heard this before but don’t understand the botany. My intuition would say that after the leaves fall off the sap flow would be less and the tree would bleed less (as it is closer to winter dormancy). Could you elucidate? Thanks
Frankly I don’t understand the botany either, why Japanese maple is different from other trees is mystifying. Vine maples are similar, they bleed. So do some roses. Most deciduous trees don’t seem to bleed much from winter wounds, or they do for a short time and then they stop. Maybe some arborist could chime in here and educate all of us?