Baptisia is a genus in the legume family, Fabaceae. They are flowering herbaceous perennial plants with pea-like flowers, followed by pods, which are sometimes inflated. They are native to woodland and grassland in eastern and southern North America.
There are two plants of the genus Baptisia common to North America, blue false indigo (B. australis) and wild white indigo (B. alba). These 5-petaled flowers feature a broad upper petal (known as a banner), two lower petals spread out to the side (wings) and two more petals fused together and curled around the flower’s reproductive parts (the keel). Most thrive in full sun and will form a large clump over time. Choose your location well as they have a deep tap root and are not easily transplanted once established. Besides the lovely blooms which attract pollinators, I like that they are deer resistant and have attractive foliage throughout the summer, even in drought. Photo below shows two clumps initially planted as only a few spikes each but growing to cover about 4 feet across each over ~7 years. Plant where they'll have space to spread.
The common name for Baptisia australis, false indigo, refers to the fact that flowers were used to create a blue dye. In my garden the blue Baptisia bloom first, in May, followed by the yellow in June. They will tolerate some shade but bloom best in sun.
Due to their size and strength bumble bees are well adapted to access the nectar and pollen within these uniquely shaped flowers. Bumble bees grip the keel with their mid and hind legs, using the leverage produced to propel them forward into the heart of the flower where they can access nectar. This has the benefit (from the flowers’ perspective) of lowering the keel and exposing the bumble bees’ fuzzy abdomen to the pollen-covered anthers.
According to Justin Wheller of the Xerces Society, Baptisia plants produce their blooms on long stalks (known as racemes). Blooms mature from the bottom up. As the blooms mature, older flowers are more pistillate (female), producing more nectar than pollen. Bumble bees will approach the stalk and land on the lower flowers first — seeking higher nectar rewards. They will then work their way up, ending with the more pollen-rich staminate (male) flowers at the top. As they move to the next stalk, pollen attached from the staminate flowers of the previous stalk is then transferred to the pistillate flowers of the current stalk.