Oak Leaf Galls: Harmless Annual Phenomenon

Tiny balls on oak leaf undersides falling like rain are leaf galls—caused by tiny wasps or mites. They're cosmetic only, not a health threat.

Gall Biology

• Insect lays eggs, secretes chemical causing leaf tissue to form protective chamber
• Larvae develop inside, emerge as adults
• Galls detach, fall to ground (hence "raining" sound)
• Populations cycle wildly—abundant one year, absent the next

Management Reality

• No practical control needed or effective
• May cause slightly earlier leaf drop
• Zero long-term tree health impact
• Raking galls doesn't reduce next year's population

Your 8 oaks are fine. This is normal oak-insect ecology. Enjoy the seasonal curiosity without intervention.