Plants perennial herbs, with deep, woody taproots or rhizomes. Stems erect or loosely ascending from a spreading base, usually branched (sometimes only at or near the base), unarmed, glabrous or hairy, sometimes minutely gland-dotted, the lowest nodes sometimes leafless or with small, scalelike outgrowths. Leaves alternate, pinnately trifoliate, the lower leaves occasionally appearing palmately trifoliate or simple, subsessile or short- to long-petiolate. Stipules mostly lanceolate-triangular to linear or the uppermost hairlike (those at the lowest, often leafless nodes sometimes broader and partly fused), attached at the base, mostly shed early; stipels absent. Leaflets elliptic to lanceolate, narrowly elliptic-lanceolate, or broadly ovate, the terminal leaflet usually somewhat longer than the lateral leaflets, all rounded at the base, bluntly to sharply pointed at the tip, the margins entire, short-hairy, the surfaces variously hairy, the undersurface sometimes also sparsely gland-dotted, the venation pinnate. Inflorescences axillary, dense spikelike racemes, variously elongate (at least at fruiting) to short and headlike, long-stalked, the bracts linear (sometimes above a short, expanded base) to lanceolate, hairy, shed early, the flower stalks 1–3 mm long; bractlets absent. Calyces 1.7–4.5 mm long, the tube bell-shaped, shorter than to longer than the lobes, 5-lobed, the lobes ascending at flowering, becoming slightly elongated and more spreading at fruiting, all similar or the lowermost lobe somewhat longer than the others. Corollas papilionaceous, usually blue to purple or lavender (the keel usually darker at the tip), rarely white, the banner with the expanded portion sometimes having white and yellowish green markings toward the base, ovate to obovate or nearly circular, tapered to a stalklike base, rounded to shallowly notched or broadly and bluntly pointed at the tip, the margins and tip curved or curled back, the wings slightly shorter than to as long as the banner, the expanded portion angled or curved over the keel, asymmetrically oblong to oblong-obovate, with a small auricle at the base, stalked, the keel shorter than the other petals, fused to the wings toward the base, short-stalked, boat-shaped, oblong to oblanceolate, only slightly curved upward, rounded at the tip. Stamens 10, the filaments all fused or 1 of the filaments more or less free above the midpoint, the free portion of alternating longer and shorter filaments, the anthers all similar and attached at the base (in O. pedunculatum) or in 2 alternating series (in O. onobrychis), those of the longer filaments attached at the base and those of the shorter series attached toward the midpoint, all yellow. Ovary short, asymmetrically ellipsoid to ovoid, very short-stalked, the style slender, often strongly curved, glabrous except for an inconspicuous ring of short hairs at the tip, the stigma small and terminal. Fruits modified legumes, asymmetrically ellipsoid or ovoid, slightly flattened, sessile or nearly so, short-tapered to a beaked tip, leathery or hardened, the surface glabrous, lacking gland-dots, strongly wrinkled, indehiscent (sometimes dehiscing irregularly with age after being shed), 1-seeded. Seeds oblong-elliptic to somewhat kidney-shaped in outline, somewhat flattened, smooth, somewhat shiny. Eight to 11 species, U.S., Mexico.

Traditionally, Orbexilum, Pediomelum, and Psoralidium were included in a broadly circumscribed Psoralea L. (Steyermark,1963), but they are now recognized as distinct genera, mainly following Grimes (1990). Psoralea in the strict sense is a genus of about 50 species restricted to southern and eastern Africa. The most important morphological characters within the complex of genera are found in details of the fruits. Orbexilum is distinguished from these other genera by the pinnately trifoliate leaves and wrinkled fruits exserted beyond the calyces.