Wildflowers Found in Oregon

Mossy Rose Gall

Plant galls come in a fascinating variety of strange forms, textures and colors. Some are irregular, bumpy, or warty; others are smooth and spherical. Some galls sport thick growths of fuzz, hair or spines. One of my favorites is the aptly named mossy rose gall - it occurs on rose and looks like moss. It never ceases to amaze me that a rose plant can produce a growth that looks like moss just because of a tiny wasp larva. Galls result from an intricate interaction between two living organisms. The gall-maker (insect disease, mite) causes the plant to change the course of normal growth and modifies growing tissue into a special swelling that surrounds the gall-maker. In the case of mossy rose galls it is a small cynipid wasp. Despite their unsightly appearance, most insect galls do not seriously affect the vigor of healthy plants. Mossy rose galls formed on the leaves of the rose are harmless.