I am NOT an expert on pruning...but I see nothing wrong with just leaving it ...it may be more bushy than upright but in zone 5a it likely won't get huge anyway and I personally like all types of Jm growth patterns ... I would think chopping off half your tree at anytime would not be a great idea but I really don't know how big it is.. a smaller diameter branch chopped off when totally dormant mid winter would probably be ok but not necessary and the tree may look like it is unaturally listing for many years IMHO...If it is a fairly large diameter established tree 4 or more years old I would give that thought some pause ...I am sure the male and female sizzorhands in this group may have differnt opinions .David

I'm going along with David on this one. While a perfectly symmetrical Y-shaped crotch is not exactly ideal, it is far less of a concern on a Japanese maple than it can be on other trees. In fact, less than ideal branch crotches are often SOP on J. maples - it's part of the growth habit of the trees and a feature that often provides much of their sculptural interest as they mature.

I wouldn't prune at all. Just make sure the tree doesn't experience any heavy snow (or ice, if that's common) loads that would put unnecessary stress on the branches and by translation, the joint. And that's really something you want to watch out for regardless of the branching position anyway.

I'd agree with these folks as well unless you intend on training the tree in a specific manner. Since maples in general are opposite rather than alternate, Y shaped splits are fairly common when the terminal buds are trimmed or snipped back. In fact some of the most attractive maples I've seen have had Y shaped splits near the base before broadening to a vase shaped small tree.

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Dax

Thanks for your replies everyone. After reading what you all had to say and looking around town at other people's trees, I'm happy to be able to just leave the tree alone. Bloodgoods, which are what most folks seem to have out here, seem to shape themselves quite nicely.

A few years ago I would have agreed with the above posters and let it be. Since than I have learned otherwise. Narrow crotches, down low, can spell almost certain disaster....eventually. Wet snow or ice buildup is what will take them down. Here is an example from my garden.
I have more.

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