Great Blue Lobelia, Lobelia siphilitica

Great Blue Lobelia

Lobelia siphilitica

Sun Shade:
Bloom Time: Summer
Zones: 3, 4, 5
Soil Conditions: Clay, Loam, Sand
Soil Moisture: Moist, Medium
Color: Blue
Fragrance: No
Height: 1 - 4 feet
Spacing: 1 foot


Great Blue Lobelia (Lobelia siphilitica) or Blue Cardinal Flower, Lobelia siphilitica, typically grows in moist to wet locations along streams, sloughs, springs, swamps, meadows and in low wooded areas. 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 feet tall. Finely-toothed, lance-shaped, light green leaves (to 5 inches long).

The blooming period occurs from late summer into fall, lasting about 2 months. Afterwards, the flowers are replaced by capsules containing small seeds. These seeds are probably distributed by wind or water to some extent. The root system consists of a central taproot, from which occasional basal offshoots are produced.

Typical habitats include moist black soil prairies, soggy meadows near rivers, low areas along rivers and ponds, floodplain and bottomland woodlands, woodland borders, bottoms of sandstone canyons along streams, swamps, fens, gravelly seeps and springs, ditches, and moist areas of pastures. Great Blue Lobelia can be found in both disturbed areas and high quality habitats.

Easily grown in rich, humusy, medium to wet soils in full sun to part shade. Will tolerate full sun in cool, northern climates, but otherwise appreciates part shade.

Plant Notes and Herbal Uses
  Divide clumps in spring as needed.
  May self-seed in optimum growing conditions, forming attractive colonies.
  Needs constant moisture.
Further Information

Wild Ones of the Fox Valley Area
Prairie Nursery
Wisconsin DNR
Wisconsin Native Plant Nurseries