is a tree or shrub, with dense clusters of evergreen leaves, and short, stout, woody branches. Leaves are pinnate, divided into an even number (4 to 8) of short leaflets which are linear, or slightly wider towards the upper end. Leaflets are rounded at the tip and have a tiny spike at the apex. Surfaces are hairless, smooth and somewhat shiny. Opposite leaflets fold together in hot or dry conditions, and at night. Leaflets have a lengthwise midvein and branched side veins, all slightly raised.
Flowers are quite large in relation to the leaflets, up to one inch in diameter; they have five lance-shaped, spreading, purple or bluish petals separated by five shorter, wider, cupped sepals. At the center are ten stamens - white filaments and yellow anthers - and a green pistil of about the same length.