That is occluded wood from the two branches growing so close together......they have actually sort of fused together. Very narrow joints like this are not uncommon with Asian maples and are usually not of major concern. However, they can be a collection point for debris and even water under some circumstances and you should take care to make sure the area is clean and as dry as possible (good luck with that in this climate!!). Sometimes areas that are subject to a high and consistent moisture level in these situations will encourage some fungal issues.

Check to make sure the area is still very firm and not soft or squishy. That would indicate a serious problem.

Thanks so much for the Informative response. I have checked it out, and the wood is solid underneath the weeping. I’ll keep an eye on it. Glad that I don ‘t have to amputate at the moment!

Even though there is a bark ridge of sorts the surface gap and weeping makes me think there is an interior gap, rather than a continuous, secure joining. I'd have a tree guy look at it, in case it needs to be wired together. If it split apart later a large section of the tree would be lost suddenly.

Also the tree seems to lack the usual foliage density of normal habit Japanese maples, and there seems to be smaller, paler leaves over on the right side of the view shown. So I am not sure the specimen actually is in peak health.

Embothrium-

I don't believe it's a Japanese maple. It was about 10' high when I moved here 12 years ago and it's about 25' high now. I have thinned out the limbs over the years, because the density of the foliage and the spreading crown prevented much light from getting through to my courtyard. Also, you shouldn't judge the leaf density and health from the photo as the fall weather has caused it and its similar mate to drop the majority of their foliage.

However, I will reinspect it, and will also see if my arborist guy can come check it out. Thanks.

It looks like it could split away during the next good snowfall.

It could......but I doubt it will :-) There is really nothing there to catch a heavy snow load. And if it hasn't experienced a lot of snow in 15 years without issue, I doubt it is going to be a major concern now.

Kudzu, are those red leaves attached to that tree? Any chance of a close up of the foliage? We could perhaps nail down a better identification. I see what looks to be Japanese maple foliage in that photo.......

gardengal-

I think you're right that it's a Japanese Maple. I have quite a few maples that were planted before I bought the house and a number of them are not Japanese...but on reflection, I think this one is. Here is a photo of the leaves:

Excellent leaf color.

What to do is the question. Most yard trees I would never cable. These stay relatively small so it does not seem life threatening to me.

Until it started growing mushrooms or feeling soft would you all really DO anything?