That sucks. Somehow it did not damage the house. I can relate to an ash splitting...someplace around here I got a pic of one across my driveway near the El Camino.

I am thinking your tree had a spot in the crotch water got into a year or so back and started some rot. It would have just continued down and rotted out more until it fell. Thankfully it happened this year and not when the tree was larger.

If you cleaned and dried out that mushy spot one sealer is as good a guess as any. For something which would be encapsulated in a short time what to do is nothing. The current authority in the tree world, Dr Shigo says use nothing, the inactive structural wood of the tree would handle itself.....somehow.....like my deck does I guess. (I'm just special and don't understand I suppose) That split is going to take a decade to be encapsulated minimum so I support your action.

More to the point and away from wound sealing theory and where I suspect I will agree with most.

That tree has some issues. One is the structural problem and almost certain rot that wound will invite in sealed or not. Two is Emerald Ash Borer. Unless you plan on treating the damaged tree with some terrible insecticide which no one guarantees will stop the bug it seems all true ash trees east of the Rockies are going to succumb to the bug.

My vote is to remove the tree before it gets larger and becomes more of a hazard. Sucks. I love ash. Just plant something else.

I wonder what role, if any, the rotted untreated beam resting in the crotch might have played. It looks like it might have been interfering with the proper upward growth of the bark ridge in the crotch.

This post was edited by tenacre on Tue, Jul 29, 14 at 9:31

Thanks for the replies. That dark spot is actually under-exposed and is mostly bark, but I get your points. The remaining part of the tree seems healthy, so I guess I'll just wait and see what happens.