Ouachita Indigobush

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 upright shrub 3 to 6 feet tall and as wide, and a few reach about 9 feet. Each leaf runs 3 to 9 inches long, with 9 to 13 grayish green leaflets.

Slender spikes 4 to 8 inches long, alone or in clusters of two to four, open from April into June. The tiny flowers are purple with yellow anthers, and butterflies visit them. Like other amorphas, it bears small pods that ripen light brown in mid to late summer. Each is about a third of an inch long and holds a single seed.

It grows wild only in the Ouachita Mountains of west-central Arkansas and southeastern Oklahoma. Its home is rocky clearings along creeks, stream banks, rocky ridges and glades, and dry sandstone slopes. NatureServe counts about 56 populations, most of them small, and logging, grazing and road building threaten them.

How to grow Ouachita Indigobush

Ouachita indigobush takes full sun or part shade, in a well-drained soil that is average to dry. It does well in poor, sandy ground, and it takes drought and holds a bank against erosion. Set plants 3 feet apart and 3 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. It needs little care once rooted, and it can seed itself around the garden.

Each flower carries both male and female parts, so there are no male and female plants to pair. Leaf spots, rust, powdery mildew and canker can turn up, though none is serious.