allelopayhy

Asked July 22, 2019, 12:31 PM EDT

can a black walnut growing up through my blue spruce affect it ? i have this situation and the spruce is starting to discolor at the top. that is ten feet of a twentyfive foot tall tree.

Washington County Minnesota blue spruce black walnut horticulture

1 Response

Spruce are on the lists of plants susceptible to juglone, the toxin in all parts of a black walnut. So it is possible. However, I'd expect the tree to appear generally stressed, not just the top 10 feet of it. Read here:
https://hort.extension.wisc.edu/articles/black-walnut-toxicity/

I'll also add that a mature blue spruce (25 feet) will probably start to show signs of the cluster of diseases that make blue spruce a poor choice for a landscape plant. These include Rhizosphaera needle cast and Cytospora canker. Read here:
https://extension.umn.edu/trees-and-shrubs/choosing-evergreens-your-landscape
https://hort.extension.wisc.edu/articles/rhizosphaera-needle-cast/
https://extension.illinois.edu/focus/index.cfm?problem=cytospora-canker-of-spruce