This erect, multi-stemmed, deciduous shrub has spikes of fragrant, purplish flowers and is perfect for areas where other plants struggle to take hold, establishing itself in a wide range of moist to dry soils in full to part sun. Typical growth is 8 to 10 feet tall and wide, although it can be pruned heavily in late winter or early spring to encourage a more-compact size and habit. It’s well suited for underplanting with shorter shrubs that will help contain it and hide its bare lower stems, such as snowberry (Symphoricarpos albus), New Jersey tea (Ceanothus americanus) or dwarf bush honeysuckle (Diervilla lonicera). Though native throughout much of the US and northern Mexico, it’s an unusual and unique shrub in domestic landscapes. It reportedly has a limited range in Ohio, including land along Lake Erie and the Ohio River and other isolated areas, such as Killdeer Plains.
 
While it’s considered aggressive in the northeast and northwest US, it’s better behaved in the Midwest. The oval-shaped leaflets clustered on the upper third of the stems resemble those of the black locust tree and give the plant a feathery, tropical appearance that contrasts beautifully with surrounding vegetation. In early summer, small, nectar-rich flowers with yellow-orange anthers are borne in racemes far above the fine-textured leaves, which are similar in appearance to those of leadplant (Amorpha canascens). The legume pods mature in the fall to add cold-season appeal.
 
Indigo bush has great wildlife value, attracting bees and butterflies, hosting several Lepidopteran species, and providing a fall food source with its seeds-- all while fending off deer!  Indigo bush has no serious pest or disease issues. With all of these attributes, it’s almost criminal not to substitute Japanese barberry and other invasives with indigo bush to create a fast-growing native hedge or windbreak.
 
Like other members of the Pea family, the roots of indigo bush associate with nitrogen-fixing bacteria to improve poor soils. The genus name is Greek for “formless” and refers to the single-petalled flowers, which are different than other flowers of the Pea family. The species name comes from the Latin word frutex, meaning “shrub,” in reference to its shrubby form. The plants do contain indigo pigment, but the quantity is too small for commercial use - another common name is false indigo (different from the false blue indigo plant in the Baptisia genus).
 
Ohio botanist Jim McCormac shares adventurous tales of searching for the rare indigo specialist, the Amorpha Borer (pictured here), a beetle that poses as a yellow jacket and lays its eggs only on indigo bush.
https://jimmccormac.blogspot.com/search?q=amorpha+borer+strikes+again
 
The developing beetle larvae feed on the pulp inside the stems, with adults emerging August through September when they seek floral nourishment, heavily favoring late boneset (Eupatorium serotinum), common boneset (Eupatorium perfoliatum), white snake root (Ageratina altimssima) and plants in the Solidago genus (goldenrod) that are in bloom in these months
 
Cheryl Harner’s favorite Amorpha specialist is the golden-colored southern dogface butterfly, which bears the silhouette of a poodle.
(https://cherylharner.blogspot.com/2010/08/amorpha-made-beetle.html)
 
Native habitats include stream and pond edges, open woods, roadsides, and canyons. Plant as a screen, hedge, or background plant; in rain or woodland gardens; and along the banks of waterways. Looks best when massed.
 
Plant Characteristics:
Grows 6-12’ tall and wide.
 
Prefers full sun but tolerates part shade.
 
Grows in a wide range of moist to dry soils; tolerates wet, dry, and poor soils. Spreads easily in moist areas.
 
Single-petalled, ¼” flowers have 10 protruding stamens with orange-yellow anthers. Flowers bloom in spike-like clusters April-June. Flowers are followed by fruits in ½” pods with 1-2 seeds that mature July-August.
 
Pinnately compound leaves are 4-12” long with 13-25 smooth-edged, spiny-tipped leaflets in a feather-like pattern. Individual leaflets are up to 2” long and hairy.
 
Multiple stems are covered with gray to brown bark.
 
Wildlife Value:
Larval host to the clouded sulphur, gray hairstreak, hoary edge, Io moth, marine blue, silver-spotted skipper, and southern dogface. The plentiful seeds are a food source for bobwhite quail. Attracts bees, butterflies, and beetles. Highly deer resistant.
 
Medicinal, Edible, and Other Uses:
The fruits contain properties that have shown promise in treating diabetes.