The place to identify and learn about galls on plants in the US and Canada.
What the heck is a gall?!
Plant galls are abnormal growths of plant tissues, similar to tumors or warts in animals, that have an external cause--such as an insect, mite, nematode, virus, fungus, bacterium, or even another plant species. Growths caused by genetic mutations are not galls. Nor are lerps and other constructions on a plant that do not contain plant tissue. Plant galls are often complex structures that allow the insect or mite that caused the gall to be identified even if that insect or mite is not visible.