What’s causing Japanese maple’s defoliation?

Q: The mature Japanese maple in my yard was just starting to leaf out when the April freeze hit. At that time, it dropped about half its leaves, and they do not appear to be re-budding.

Previously, it has appeared very healthy and had a nice thick canopy. I water it about once a month during the summer, and watered especially deeply and more frequently during last year’s heat dome. I do notice that the tree has a fair amount of lichen growing on it. It also has a lot of dead twigs on the branches that lost leaves. The main small branches are green under the bark though.

Is the tree in danger of dying? Should we fertilize it this spring or summer to help compensate for the missing photosynthetic ability? If so, what should we use and how much?

A: There are at least two possibilities to explain why your maple has defoliation. One is the late, unexpected freeze, just as foliage was emerging. The foliage won’t be replaced this year.

A second, more serious possibility would be a soil disease called verticillium wilt, a fungus that causes defoliation. It is not treatable and is always fatal to the tree. This can be diagnosed only in a lab by examining a branch and soil testing.

It’s your call whether to do testing now or wait to see if the tree loses more leaves, giving it another year and hoping for a warmer spring.

This entry was posted in Gardening and tagged , , , , , , , , , , . Bookmark the permalink.

Please Leave Your Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s