Q: I saw these weird things hanging off a tree sapling while walking in Mason Mill park in early May. They don’t seem to belong to the tree. Can you tell me what they are?
A: They are oak apple galls. The galls are caused by a tiny wasp who lays her eggs on a developing leaf bud. Hormones in the developing eggs cause the tree tissue to form a spongy mass with a thin papery shell.
The galls don’t hurt the tree. If you had one in your yard you could pick them off if they are objectionable.
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