Every year I receive numerous questions about strange, misshapen growths on the leaves or stems of trees.  These growths, called galls, are often the result of insect egg-laying or feeding. Galls themselves are tumor-like growths produced by the plant in response to chemicals injected into the plant by the adult or larval gall-making insect.  The shape, size and form of the gall is determined by the precise chemicals chemicals used by each species of gall-maker. The mechanisms of gall formation, and how these chemicals result in very distinctive… Read More →