Blue Wild Indigo
Bean family (Fabaceae)
Description: This native perennial plant forms a branched bush about 3-5' tall, although it is herbaceous. The compound leaves are trifoliate and can be green, bluish green, or greyish green. They are devoid of hairs and their margins are smooth. Each leaflet is oblanceolate, although bluntly pointed toward the tip. The flowering stalks are erect and organized as racemes. The showy flowers are varying shades of blue, about ¾-1" long, and have a typical structure for a large pea flower. They bloom during the late spring for about 3 weeks. There is no scent to the flowers. Blue Wild Indigo continues to grow after the blooming period. The root system consists of a central taproot, with short rhizomes that help this plant to spread. This plant can be very long-lived, and remains attractive throughout most of the growing season. The rather large seeds fall to the ground only a short distance from the mother plant.
Cultivation: The preference is full sun, average moisture levels, and rocky soil that isn't too alkaline. Blue Wild Indigo grows well in deep loamy soil, but it will have greater difficulty competing against other kinds of plants in a naturalistic setting. Considerable variations in moisture are tolerated. Like other wild indigos, this plant is somewhat slow in becoming established, but not particularly difficult. It will add nitrogren to the soil.
Range & Habitat: Blue Wild Indigo may be native to NE Illinois in the Chicago area, or it could be a horticultural escape (see Distribution Map). In either case, this plant is extremely rare, and perhaps extirpated from the state as wild populations have not been observed in many years. It has been observed in rocky open woodlands, mesic black soil prairies, and gravel prairies. In other states, such as Indiana, it has been observed along the rocky banks of rivers.
Faunal Associations: Little information is available in Illinois, but it is likely that Queen bumblebees are important pollinators of the flowers. Other long-tongued bees may visit the flowers occasionally, such as Miner bees. Like other wild indigos, the foliage of this plant may be consumed by the caterpillars of a few species of skippers and related insects, including Erynnis baptisiae (Wild Indigo Duskywing), Achelerus lyciades (Hoary Edge), Dasylophia anguina (Black-Spotted Prominent), and Colias cesonia (Southern Dogface). The adults of Apion rostrum (Wild Indigo Weevil) feed on the flowers and leaves, while the grubs of this insect feed on seeds. Generally, mammalian herbivores avoid this wild indigo and others because the leaves are somewhat poisonous.
Photographic Location: The above photographs were taken from the webmaster's wildflower garden in Urbana, Illinois.
Comments: This is a favorite garden plant because of its showy flowers and attractive foliage. There is a subspecies of this plant, Baptisia australis nana, that occurs in prairies to the west of Illinois. It is smaller in overall size, but has larger, more fragrant flowers, and prefers drier conditions than the typical species. Blue Wild Indigo is more common in the southeastern US.