menyanthes trifoliata

bogbean \bogbean\ n. a perennial plant of Europe and America (Menyanthes trifoliata) having racemes of white or purplish flowers and intensely bitter trifoliate leaves; often rooting at the water margin and spreading across the surface; -- called also bog myrtle, water shamrock and marsh trefoil.

buckbean \buckbean\, Buck bean \Buck" bean`\(b[=e]n`). (Bot.) A perennial plant (Menyanthes trifoliata) of Europe and America which grows in moist and boggy places, having racemes of white, reddish, or purplish flowers and intensely bitter trifoliate leaves, sometimes used in medicine; marsh trefoil; -- called also bog bean. It often roots at the water margin and spreads across the surface.