This plant is practically indestructible—it will remain vigorous long after the gardener has thrown in the trowel. In fact, once it is well established you almost need a backhoe to move it; with this in mind, plant false indigo in well-drained soil in a spot where you want it to stay. In full sun, false indigo blooms profusely and needs no staking.
It will do almost as well in 3 to 4 hours of light shade, with bloom only slightly diminished, though plants may require staking. Start new plants from seeds. If you allow the seeds to ripen and fall, you may find seedlings close to the base of the parent plants; keep your eyes open for telltale gray-green leaves.
False indigo has brilliant blue, pealike blossoms on 10- to 12-inch flower spikes that appear around the time peonies bloom. Flowers are followed by attractive seedpods that start out green but gradually turn black and persist until fall. The grayish green foliage has a cool, pleasant, shrublike appearance and remains appealing until frost cuts it down. Its long-lasting foliage makes false indigo a useful background for plants that are later blooming.
Shrublike false indigo makes its presence known in any mixed border. It can be surprisingly effective as a seasonal hedge or foundation planting, serving the visual function of a shrub in three seasons and disappearing in winter. Try it where ice sliding off a roof prevents you from growing shrubs.
ZONES: 3–9
BLOOM TIME: Midspring to early summer
LIGHT: Full or part sun (tolerates 3 to 4 hours of light shade each day)
HEIGHT: 36–48 inches
INTEREST: Brilliant blue flowers; attractive gray-green foliage; black seedpods