Triphragmium ulmariae

Triphragmium ulmariae is a species of rust fungus in the family Phragmidiaceae. It causes meadowsweet rust gall, which develops as a chemically induced swelling, arising from the lower surface of the meadowsweet leaves.

Life cycle

The fungus grows in the petioles and midribs of the perennial plant meadowsweet, a member of the rose family, causing swelling and distortion. Sori develop with bright orange spores. The rust's spores reach the new meadowsweet plants via air movements.
The rust has a severe effect on the survival of meadowsweet seedlings.