Amorpha nana

Native

Uncommon

Moist. Prairies. Full sun.

Early June to late July

Violet to purple

12″ to 40″

This is an erect, compact, bushy, perennial shrub that rises on one or a few stems from a woody root crown. It is usually 12″ to 24″tall, though tall individuals may reach 40″ in height. It reproduces by suckers.

The bark is gray to brown and more or less smooth.

First-year twigs are sparsely hairy to almost hairless. Second-year twigs are hairless.

The leaves are alternate, deciduous, and 13 ⁄16″ to 3½″ long. They are pinnately divided into 9 to 27 leaflets. They are on ⅛″ to 5 ⁄16″ long, sparsely hairy leaf stalks.

The leaflets are oblong to elliptical or inversely egg-shaped, ¼″ to ⅜″ long , and ⅛″ to 3 ⁄16″ wide. They are rounded or tapered at the base and blunt to rounded at the tip. The leaf tip is sometimes notched and has a short, sharp, abrupt point. The upper surface is dark green and hairless. The lower surface is pale green and is usually hairy along the midvein and at the margins. The underside is also conspicuously dotted with sunken glands. The margins are untoothed.

The inflorescence is a single, erect, spike-like raceme at the end of the stem and branches. The racemes are erect, densely flowered, 13 ⁄16″ to 3⅛″ long, and ⅛″ to ⅝″ wide.

The individual flowers are on 1 ⁄32″ to 1 ⁄16″ long, moderately to densely hairy stalks. There are 5 green sepals fused for most of their length into a bell-shaped, ⅛″ long tube (calyx), then separated into 5 narrowly triangular lobes. The calyx lobes are at least half as long as the calyx tube. The corolla is a single 3 ⁄16″ to ¼″ long, violet to purple petal. The petal is tubular near the base, unfolded near the tip to form a protective covering over the stamens and pistil. There are 10 stamens with purple filaments united near the base and yellow to orange anthers protruding well beyond the corolla.

The fruit is a brown, hairless, ⅛″ to 3 ⁄16″ long pod with a single seed. The pod matures late July to mid-September.