Great St. Johnswort is a tall perennial with large yellow flowers much like false sunflower in effect. Grows 3-5' tall. Flowers from July-August. Prefers full sun in moist sandy to clayey soil. Wet meadows and floodplains. Attracts many pollinators but especially bumble bees. Spreads to form a loose colony. Seed-heads remain attractive in winter. Zone 3-6. Ecotype unknown.