Photo: Eric Hunt, CC BY-SA 4.0 · Wikimedia Commons

Shining Indigobush

Amorpha nitens

Also called shining false indigo, dark indigobush.

A rare indigobush of southern stream banks and wooded slopes, with glossy leaflets and dark purple spikes lit by orange anthers in spring.

RareShowy flowersTolerates wet soilNitrogen fixing

Type: Shrub
Mature height: 3–10 ft
USDA zones: 7–9
Growth rate: Fast
Sun: Full, Part
Soil moisture: Dry, Average, Wet
Grows wild in: Stream banks, floodplain forests, rocky ground and rich moist slopes
Native range: 10 states, north to Illinois, south to Louisiana and west to Oklahoma
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Alabama, Arkansas, Georgia, Illinois, Kentucky, Louisiana, Missouri, Oklahoma, South Carolina and Tennessee
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Shining indigobush is a shrub of the Southeast, from southern Illinois and western Kentucky to South Carolina and west to eastern Oklahoma. It grows along creeks and rivers, on wooded slopes and bluffs, and at the edges of glades. Its leaflets are glossy above and turn black when dried, while those of our indigobush are dull. It is common only in Arkansas. Illinois lists it as endangered, and NatureServe ranks it critically imperiled in Missouri and South Carolina. Mass it along a stream bank or at the edge of a wooded slope, where its dark spikes show in spring.

Size, growth and what to expect

No source rates its growth, so our growth estimator uses the fast rate of our indigobush, about 2.75 feet a year while young. It makes an erect or sprawling shrub 3 to 10 feet tall. Its leaves run 4 to 8 inches long, with 7 to 19 glossy leaflets up to nearly 3 inches long.

Erect spikes 2 to 10 inches long open from April into June. Each small flower has one purple-black petal and ten long stamens tipped in orange. The smooth pods, about a quarter inch long with a single seed, ripen from June into August.

It grows wild from southern Illinois and western Kentucky south to Georgia and South Carolina, and west to eastern Oklahoma and Louisiana, where it may be gone. Its home is moist woods along creeks and rivers, bottomlands, ravines, bluffs, rocky slopes and glade edges, often over limestone. Dams, clearing and invasive plants such as Japanese honeysuckle threaten it.

How to grow Shining Indigobush

Shining indigobush grows in part shade or sun, in an average to moist soil. It takes the wet ground of stream banks and bottomlands, and it also grows on rocky limestone slopes. Set plants 5 feet apart and 5 feet from a wall. At its size it can go within 15 feet of overhead wires.

Saplings ship bare-root or potted. Plant them dormant, in a hole wider than the roots and no deeper. Set the crown at the soil line, put the native soil back in, and keep the mulch clear of the stems. Other amorphas have a hard seed coat that a winter outdoors helps to soften. Sow the seed outdoors in fall, about a quarter inch deep.

Water weekly through the first summer, then only in long droughts. Deer browse it, so cage young plants where deer are many.

Each flower carries both male and female parts, so there are no male and female plants to pair. Like other amorphas, it fixes its own nitrogen, so skip fertilizer.

Heights and zones are typical ranges for the species in cultivation; local conditions and seed source shift them.

Sources (11)