If you don't prune it now, it'll only get worse.

Thanks... Bummer... I was afraid that was what you'd say...

Sorry to deliver bad news. The tree does have a great shape, but that branch is only going to cause problems for the trunk if not removed.

Prune the branch just above the collar (the "swell" at the base of the branch where the two branches join). If you have them, I've been told by an "old timer"/semi famous in these parts Japanese Maple propogater (is that a word?), the concave pruners make a cut that is easier for the tree to heal on larger branches/older wood.

Blake

Thanks for the advice, Peapod. I do have a concave pruner, and was actually wise enough to use it!

TG - you should AGGRESSIVELY prune the top back or your tree is going to shed the lower branches. Prune everything in the top 1/3 of the tree back to 1 set of 2 buds, and remove heavy branches. Notice how unnatural it looks when branches at the top of the tree are heavier than those at the bottom. You need to help the tree along. Also, you should correct any areas where 3 or more branches converge. Only 2 branches should form Ys, not Ys + an extra branch. It is the tree's natural tendency to grow this way, but allowing the habit quickly spoils the look of containerized trees.

Al

Al, I'm delighted that you took the time to offer your expertise here. I'm a real novice at knowing how to properly prune these containerized maples. I want to make sure I understand your advice. Are you suggesting that I cut off about 1/3 of each branch to the nearest set of two buds, or are you telling me I should cut every branch back to the most proximal set of 2 buds on each branch? As for eliminating any branches that are forming Y+1's, is the decision on which of the +1's I should eliminate purely aesthetic, or are there some general rules to follow for that, too? Finally, can you explain to me what you mean by remove "heavy" branches? (Please let me know if more photos would be helpful and thanks again for sharing your expertise!)

Let's see some more pictures.

I JUST got done pruning 2 Japanese maples in the landscape for a customer, less than an hour ago.

You can see how the branches near the top are growing more robustly than those at the bottom because they are becoming heavier. You're going to have to restrain the tree if you want to keep the lower branches. If you don't, shedding is inevitable as the tree tries its best to grow tall/wide.

I'd remove the crossing branch w/o hesitation, then I'd start looking for ways to restrain the top with an eye toward increasing ramification (branch density). It's really difficult to try to explain how to prune containerized Acers without being able to point & explain, but I'll try.

In your 'Y + 1' way of describing the growth habit, you should be concentrating on removing either a leg of the Y or the central branch extension. Your eye will tell you which is the best to remove, and your eye will decide by the direction the tree will be growing after you make the cut. IOW, you want the branches to be headed in a favorable direction instead of into trouble, where they interfere with other branches or the natural path of other branches.

Cut back the top 1/3 of the plant very hard. You will, in most cases, want to remove the central leader back to a fine pair of branches, then remove the central leaders from those branches, and even do it again, if required. All branches in the top 1/3 of the tree should have only 1 pair of buds on it, and as the tree back-buds in inopportune places, you should rub the unwanted buds off.

Be a little less aggressive in the middle 1/3 of the tree, and prune only enough to keep the tree in bounds on the bottom 1/3. It's best to start this type of pruning & pinching when the tree is very young, but you can do it now with no problem. I can't be more specific because I'm not getting a good look at the tree, but that's how experienced bonsai practitioners keep branching well ramified yet delicate, instead of heavy.

Honestly, that tree could easily have 60% of the canopy removed, most of it near the top, and still be a very attractive tree by mid summer. The important consideration is that as you build branch density, you decrease internode length and provide yourself with myriad pruning opportunities that virtually ensure your ability to build an attractive framework.

Notice how hard I'm working to keep the top restrained while bottom branches develop:
{{gwi:10867}}
{{gwi:828}}

Al

Al, thanks for the detailed help. The tree now has leafed out fully, so it's more difficult to judge its branching. I want to make sure I understand your instructions. When you say "All branches in the top 1/3 of the tree should have only 1 pair of buds on it" are you suggesting that I cut each branch from the top of the tree back to the first (i.e most proximal) pair of leaves on each stem, or am I supposed to go even shorter than that? Sorry to be dense here, as I'm sure this is easy to grasp if you see it demonstrated once, but not so easy when relying on words to describe the process. The problem is I have not found any printed source of material that describes these pruning tips as well as you do!

I would remove a LOT of the branches at the top of the tree to prevent the top from getting coarse, heavy branches; then, reduce all the fine branches you kept to 1 pair of buds (in this case - 1 pair of forming branches, since the tree has flushed). The top will grow MUCH faster than the lower part of the tree. By restraining the top, you keep it in proportion, and more importantly, you force the tree to expend energy on the lower branches it would otherwise shed.

Al