Lobelia siphilitica

Lobelia siphilitica, or Great Blue Lobelia is an eastern US native perennial which typically grows in moist to wet locations along streams, sloughs, springs, swamps, meadows and in low wooded areas.  It is a clump-forming perennial which features light to dark blue, tubular, 2-lipped flowers with the three lobes of the lower lip appearing more prominent than the two lobes of the upper lip. Flowers arise from the upper leaf axils forming a dense terminal raceme atop stiff, unbranched, leafy stalks typically rising 2'-3' tall. Finely-toothed, lance-shaped, light green leaves (to 5" long). Late summer bloom period. The species name of siphilitica arose from the mistaken belief that the plant was of use in the treatment of venereal disease. It is sometimes commonly called blue cardinal flower.

It's easily grown in rich, humusy, medium to wet soils in full sun to part shade and needs fairly constant moisture. Will tolerate full sun if soils are moist, but otherwise appreciates part shade. Divide clumps in spring as needed. May self-seed in optimum growing conditions, forming attractive colonies.