Oak Insect Galls: Benign Wasp Nurseries on Mature Tree

Suzanne: Northern California mature oak with clustered nodules/pods on branches. Green when small, brown tennis-ball size when mature, fall off. Tree flowering, otherwise healthy.

Expert Assessment

Steve: likely insect galls (small wasps). Usually no significant health impact. Photo requested for confirmation. Asks: soft/thin-walled or hard/solid?

Key Insight

Oak galls are incredibly diverse. Texture (soft vs. hard) helps distinguish gall types. Most are harmless curiosities on mature oaks.