What’s in Bloom | Wild Indigo
June 1, 2020
Blue wild indigo (Baptisia australis) is a bushy perennial herb native to the eastern and central United States. Its asparagus-like shoots, showy racemes of deep blue to purple flowers, and inflated black seed pods give the plant ornamental interest through its growing season. Yellow wild indigo (Baptisia tinctoria), with its bright yellow flowers and purple seed pods, is similar in shape and habit but is smaller in size.
In Virginia, Baptisia australis is rare but can be found in rocky or gravely outcrops along streams in the Piedmont and mountains. Batptisia tinctoria is much more common and grows in rocky, nutrient-poor soils in forests, barrens, and roadsides across the state. Their common names “wild indigo” and “false indigo” refer to their sap, which turns dark blue when exposed to air and was used by Native Americans and early American colonists as a dye for clothing.
These Baptisia species have clover-like trifoliate leaves and grow in bushy clumps. B. australis reaches a height and spread of 3 to 4 feet and B. tinctoria remains smaller with a height and spread of 2 to 3 feet. Both species produce tall racemes of showy pea-like flowers. These racemes are up to a foot long with one-inch flowers in B. australis, while B. tinctoria bears smaller flowers in shorter racemes. In the fall, the spent stems of the plant may break away from its roots to form a tumbleweed-like mass that blows around to distribute its seeds.
Bumblebees are especially well-adapted to feeding from and pollinating Baptisia flowers, as they are large enough to grip and open the keel of the flower to access its nectar. The shape of the flower ensures that the bumblebee is brushed with pollen while it feeds. The more mature flowers positioned lower on the raceme provide the most nectar, encouraging the bumblebees to start at the bottom of the raceme and work their way up to the pollen-filled immature flowers at the top. The pollen-covered bumblebees then fly to the next raceme and pollinate the nectar-filled mature flowers, starting the feeding-and-pollinating cycle again.
Both B. australis and B. tinctoria are excellent native choices for gardens and meadows. Though they can be difficult to establish from seed due to high rates of weevil depredation, they are available as bare-root and potted plant from nurseries and are easily grown in full sun or partial shade. Once their deep root systems are established, they are durable, long-lived, tolerant of droughts and poor soil, and are deer resistant.