Tree affecting soil and shrubs?

Asked October 7, 2018, 12:15 PM EDT

For the last 4 years, our skip laurels have died in this area. Two skip laurels on the other end of the row from the tree are fine. I have noticed the tree started leaking a black substance in the last 4 years. Does the tree have a disease affecting the shrubs? I believe it is a black walnut tree. Should I cut down the tree and will that eliminate the problem? I am afraid to plant anything else in this area since I feel I am throwing away money every year. Thanks for any suggestions

Anne Arundel County Maryland

3 Responses

We are glad you asked!
If that is indeed a black walnut, that is your problem.
All parts of black walnut, including the roots that can extend far from the tree, exude a chemical called juglone. It is poisonous to many types of plants, including laurel shrubs.
Skip laurels, a type of Cherry Laurel (Prunus laurocerasus) is susceptible. Here is our page that discusses the matter in more detail, and includes a list of plants that are resistant to the juglone:


Thank you so much for your response. Since the tree has this wilt and is emitting a dark sap, is it best to take it down? If so, should I do anything to treat the soil before replanting shrubs ?

The walnut is fine. Walnut "wilt" merely means it make other plants wilt (and die.)

The black substance you see is probably slime flux, which doesn't hurt the tree. Here's the scoop on that:

If you decide to remove the tree, the juglone will remain in the roots in the soil until they break down and decompose. Can't say how long that will take. If you have the stump and larger roots removed, it will be faster because the smaller roots decompose faster. There is no way to "treat" the soil to remove juglone.

You may want to replant with plants that are in the list of plant not susceptible to juglone (at the bottom of the Walnut Wilt webpage we gave you above.)