Herbs acaulescent, to 20 cm, mostly glandular and pubes­cent throughout. Stems absent, leaves clustered; pseudoscapes 5–7 cm (when present); cata­phylls 7–9 mm, striate, clus­tered apically. Leaves pinnately 3-foliolate; stipules persistent, lan­ceolate to oblanceolate-oblong, 5–7(–12) × 2.5–3 mm, stramineous, eglandular, glabrous; petiole swollen prox­imally or not, not jointed, (30–)50–120 mm; petiolules 2 mm; leaflet blades orbiculate to obovate-trullate, lateral 2 usually asymmetrical, 1.5–2.5(–3.2) × 1–2.4 cm, base broadly cuneate or truncate, apex broadly acute, surfaces abaxially white-pubescent, adax­ially white-hirsute along veins and margins. Peduncles 2–10 cm, shorter than sub­tending petiole, glabrous proximally, pubescent dis­tally. Inflorescences disjointing in age at peduncle base, ovate to elliptic; rachis 1.4–1.6 cm, crowded, nodes 4–7, 3 flowers per node; bracts persistent, caudate-lanceolate, 5–8 × 2–3.5 mm, pubes­cent throughout or only at apex. Pedicels 1–3 mm. Flowers 12–20 mm; calyx gibbous-campanulate in fruit, 10–15(–17) mm, pubescent throughout or teeth only; tube 5–7 mm; lobes linear or linear-lanceolate, abaxial 8–8.5 × 1–1.5 mm, adaxial 6–7.5 × 0.5–1 mm; corolla white and blue-purple, ban­ner white to pale purple, oblanceolate, 15–17 × 6–7 mm with claw 4.5–5.5 mm, wings blue-purple, 12–14 × 2.5–3 mm with claw 5.5–6.5 mm, keel dark purple, 14–16 × 2.5–3 mm with claw 8.5 mm; filaments 16 mm; anthers elliptic, 0.7 mm; ovary glabrous, style glabrous. Legumes oblong-ellipsoid, 5–7 × 3.5–4 mm, eglandular, pubescent apically, beak 4–5 mm, about as long as calyx. Seed black, ellipsoid-reniform, 3.5–6 × 2.5–4 mm.

Phenology: Flowering spring.
Habitat: Shallow, rocky clay or limestone soils, shortgrass prairies, shrublands.
Elevation: 700–2000 m.

Distribution

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Tex., Mexico (Coahuila).

Discussion

Pediomelum humile, historically known from along the Rio Grande in Texas (Val Verde County) and Mexico, is very rare and on the verge of extinction. Several known populations have been destroyed by urban development in the recent past. The few populations in existence today are located near Del Rio and are all in danger of extirpation due to human influences. Pediomelum humile is in the Center for Plant Conservation’s National Collection of Endangered Plants.

Psoralea humilis (Rydberg) J. F. Macbride 1922, an illegitimate name (not Miller 1768), pertains here.

Selected References

None.

Lower Taxa

None.