Spiky growths on my Linden tree leaves - Ask Extension
Many of the leaves on my 40 year old Linden tree have spiky, red growths protruding from the top of the leaves. I think I first noticed it in early J...
Knowledgebase
Spiky growths on my Linden tree leaves #659425
Asked July 03, 2020, 2:29 PM EDT
Many of the leaves on my 40 year old Linden tree have spiky, red growths protruding from the top of the leaves. I think I first noticed it in early June. I have Japanese beetles in my yard and know that they eat the leaf tissue, but I believe this something different. What is it? Is it harmful to the tree? What, if anything, should I do about it? (I'm already brushing Japanese beetles into soapy water from my rhubarb and zinnia leaves. I have attached a picture of one of the affected leaves.
Thanks for your help. ( I am a faithful listener of the Saturday morning WCCO garden show.)
Hennepin County Minnesota
Expert Response
Those are spindle galls. They are the trees reaction to insects laying eggs on the leaves. There is nothing that you could have done and they are cosmetic but not harmful to the tree. Make sure to clean up leaves as they fall and dispose of them in case there are still unhatched eggs on the leaves. It will not cause the leaves to fall now. https://extension.umn.edu/yard-and-garden-insects/insect-and-mite-galls#eriophyid-mites-1346961
