Crown gall is a tumorous growth of tissue up to several inches or more in diameter.
It is generally found at the soil line or on roots and usually has a rough surface. Crown galls differ from natural burls. The crown gall bacterium lives in the soil and enters the plant at the site of a wound, perhaps from a shovel or a lawn mower. Once inside the plant, the bacteria stimulates gall formation. Infected plants often grow very slowly and continue to decline in vigor year after year.