Black knot fungus on ornamental plum

Asked July 12, 2019, 3:45 PM EDT

Hello, I just identified the problem with the tree in front of my house: black knot fungus. But the tree has had it for a few years. Perhaps even 10. This is the first year it finally looks bad overall. There are quite a few bare branches for the first time. I assume this tree is beyond treatment and wonder if it should come down. I'd rather not do that. I am not even certain that it is my responsibility since it is between the curb and the sidewalk, nor can I really afford to do it right now. Also, it still provides a lot of shade. Is it a danger to other trees? (During recent bad storms, it did not drop branches.)

Baltimore County Maryland disease issues black knot trees ornamental plum

3 Responses

You are correct with your Black Knot diagnosis. Here is our page on it:
https://extension.umd.edu/hgic/topics/black-knot-trees
It will eventually kill the tree but you will likely want to remove it long before as it loses it's attractiveness over time, but it could take years.
Right now would be a fine time to check with your county to see who is responsible for the tree. Dead wood can be pruned out at any time.

Here is our pruning page: https://extension.umd.edu/hgic/topics/pruning

It is not a danger to other trees other than the related prunus species listed in the first link above (plum, cherry, flowering almond, apricot, and blackthorn).

This page helps homeowners decide when it is time to remove a tree:
https://extension.umd.edu/hgic/topics/how-do-you-decide-when-remove-tree


Christine


Thank you very much. This is helpful information.
Best,
Laurie