Marsh Pea is a tall climbing perennial. The flowers are a lilac blue. The leaflets are narrow and grow in pairs; the leaves end in branched tendrils.
The plant is rare and grows in boggy meadows and fens. It was once growing freely round Lough Neagh, but may not be found there now. Look for it around Lough Erne and the Westmeath lakes. The flowers appear in June.
Marsh Pea is a northern plant. It occurs in the east of England, in Europe to northern Norway, Arctic Russia and Siberia, and east to Japan. It is also found in eastern North America.