Blue cardinal flower, also called great blue lobelia, is a perennial wildflower with unbranched stalks or branching toward the tip, often slightly winged. Flowers in leaf axils of upper stem leaves, having the typical lobelia shape with a 2-parted upper lip and 3-divided lower lip, to 1 inch long; color light or dark violet, light or dark blue or lavender, rarely white. Blooms August–October. Leaves alternate, light green, narrowly lance-shaped, 2–6 inches long, sometimes with a few irregularly spaced teeth.
Similar species: Missouri has 5 species of Lobelia, 4 of which are common: Cardinal flower (L. cardinalis) has bright red flowers. Spiked lobelia (L. spicata) has pale blue or white flowers; Indian tobacco (L. inflata) is similar, but its ovaries become inflated as the seeds ripen.
Height: to 3 feet
Habitat and Conservation
Found in wet places: banks of streams, rivers, and spring branches, margins of ponds and lakes, bottomland forests, moist depressions of upland prairies, sloughs, swamps, fens, and moist ledges of bluffs; also pastures, ditches, and roadsides. This is a popular late-blooming native wildflower for home gardening; it requires moist locations.
An alkaloid, lobeline, is extracted from several types of lobelias. It's similar to nicotine and has been used in antismoking medications. In large does, lobelia extracts can cause death. In the 18th century extracts of L. siphilitica were used to treat venereal disease, hence the species name.
Bumblebees are the primary pollinator. Because of the toxic alkaloids in its foliage, this plant is rarely eaten by mammals. Plants that grow along streams and in other wet places play in important role in preventing soil from washing away.