GALLS - These are swollen, mis-forMEd LEAVES caused by a VARIETY of pests of fungi.GALLS - These are swollen, mis-forMEd LEAVES caused by a VARIETY of pests of fungi.

Some are specific to tree types e.g. oak apple or aZAlea gall.

They are generally harmless in themselves and should be removed and burned.

See also "Yew tree gall"