Boechera pusilla

Perennials; long-lived; (cespitose); apomictic; caudex often woody. Stems usually 2–6 per caudex branch, arising from margin of rosette near ground surface, 0.5–2 dm, glabrous or sparsely pubescent proximally, trichomes simple and short-stalked, 2-rayed, to 0.2 mm, glabrous distally. Basal leaves: blade linear-oblanceolate, 1–2.5 mm wide, margins entire, ciliate along petiole, trichomes (simple), 0.4–0.7 mm, surfaces usually sparsely pubescent, rarely glabrous, trichomes short-stalked, 2- or 3-rayed, 0.1–0.4 mm. Cauline leaves: 3–5, not concealing stem; blade auricles 0–0.2 mm, surfaces of distalmost leaves usually glabrous or, rarely, margins sparsely ciliate. Racemes 6–13-flowered, unbranched. Fruiting pedicels horizontal to divaricate-descending, straight or slightly curved downward, 2–5 mm, glabrous. Flowers divaricate-ascending at anthesis; sepals glabrous or sparsely pubescent, trichomes spreading, 2-rayed; petals white to lavender, 4–5 × 1.5–1.8 mm, glabrous; pollen spheroid. Fruits horizontal or divaricate-descending, not appressed to rachis, secund, straight, edges parallel, 1.6–3.2 cm × 1.5–2 mm; valves glabrous; ovules 20–32 per ovary; style 0.1–0.4 mm. Seeds uniseriate, 1.2–1.5 × 0.8–0.9 mm; not winged or with distal wing 0.05–0.1 mm wide.

Phenology: Flowering May–Jun.
Habitat: Cracks and crevices of granitic rock outcrops
Elevation: 2400-2500 m

Wyo.

Discussion

Of conservation concern.

Morphological evidence suggests that Boechera pusilla is an apomictic species that arose through hybridization between B. lemmonii and B. pendulina; it is known only from the type locality in southwestern Wyoming.

Selected References

None.

Lower Taxa