Here's another photo!

Fungus was growing in tight branch crotch, branch came off because it was a weak crotch - does not mean there is a problem with rest of tree. Except in the second picture it looks like green "tree" may be cherry plum rootstock sprouts coming from beneath a purple-leaved plum to the right - in which case all the green-leaved stems should be cut to the ground and kept cut down.

Thanks so much for your answer! I don't know if the green is part of the purple tree; the purple is on our neighbor's property and the green on ours. It's hard to tell what's trunk and what's branch as multiple ones come up out of the ground. The tree is probably 25 feet tall or more and is over 20 years old. I hope the whole thing doesn't have to be cut down as it's beautiful and gives us some privacy (not to mention cherries!).

Thanks again for your help!
cheers -
Denise

If you're getting cherries, then it wouldn't be a cherry plum. Cherry plums produce small, red plums, often not that interesting in flavor or texture, and definitely not cherries. Otherwise the thicket of stems near a purple-leaved plum tree is a typical situation resulting from grafting of purple-leaved plums onto cherry plums. I've got a clump of cherry plum in my yard I have to keep cutting off, it came from a grafted purple-leaved plum on the other side of the fence, now cut down - but still providing The Gift That Keeps On Giving.

I've always avoided cherries and plums in my garden. For the most part, they're more trouble than they're worth.
mike