Bumps on tree

Asked May 27, 2018, 2:24 PM EDT

What are these? They are on a mature Linden (Lime or Basswood) tree. About 80 percent of the tree. They are growths on the leaves.

Deschutes County Oregon linden tree leaf galls horticulture

1 Response

The leaves on your linden have spindle galls caused by feeding of eriophyid mites from the undersides of the leaves. Eriophyid mites are very small and slightly elongated; they are a much different kind of mites than the spider mites you may be familiar with.

The leaf galls won’t damage the tree’s health or well-being. No sprays or other treatments are needed.

If you prefer to try treatment, consider hiring a Certified Arborist to spray the tree in spring, at bud break. You can locate local Certified Arborists by using your zip code at https://www.treesaregood.org/findanarborist/findanarborist.