Amorpha ouachitensis

Amorpha ouachitensis is a charming deciduous bush on the verge of extinction in the Ouachita Mountains where it was born on the outskirts of Arkansas USA. This cousin of peas and alfalfa has the amiable appearance of a not very large, somewhat spreading bush. Dressed in a lovely bluish-green foliage, it adorns itself in spring or early summer with unusual flowering that seems to sparkle. Carried on long upright spikes at the end of the stems, as surprising up close as from afar, the small purple flowers release orange stamens powdered with gold. It is not a spectacular plant, but a rare and precious species that will be welcomed in a large rock garden or in a raised bed to ensure the necessary drainage for successful cultivation.

Amorpha ouachitensis is sometimes called Ouachita false indigo, due to its origins but also to the blue dye that American settlers extracted from the flowers of this type of plant from the legume family. It is native to North America, specifically the open forests covering the mountainous massifs of Ouachita in Oklahoma and Arkansas. It is a loosely spreading bush, of quite rapid growth. It will reach about 1.8 m (6 ft) in height, a bit more in width. The foliage is composed of 10 to 19 small ovate leaflets, ranging in colour from green-blue to glaucous. Flowering occurs between May and July depending on the climate, and lasts about 3 weeks. The flowers, grouped in thin spikes of 15 to 20 cm (6 to 8 in) long, are composed of a single rolled up violet petal, releasing orange stamens with golden yellow pollen. The fruits are pods that persist on the plant for a long time in winter. The roots of Amorpha ouachitensis require well-draining soil that dries quickly. It is not long-lived in constantly humid and poorly drained areas. Its drought tolerance is quite good, after flowering. In its natural habitat, this plant easily self-seeds.

Ouachita false indigo is a wild plant that thrives on moist to dry slopes, is hardy down to -15°C, and requires absolutely no maintenance. As such it will earn its place in a large sunny to semi-shaded rock garden or in a raised bed. Natural scenes can be created by associating it with e.g. echinaceas, coreopsis, evening primroses, gauras, and grasses such as Carex comans or Stipa tenuifolia. In light woodland it will accompany symphorines and periwinkles. Its strong roots also contribute to stabilising slopes, occasionally flooded banks, and sandy soils.