Boechera atrorubens |
Boechera hastatula |
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black-flower rockcress, dark-red-flower rockcress, purple sickle-pod rock-cress, sicklepod rockcress |
Hells Canyon rock-cress |
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Habit | Perennials; usually short-lived; sexual; caudex not woody. | Perennials; short- to long-lived; apomictic or sexual; caudex often woody. |
Stems | usually 1 per caudex branch, arising from center of rosette near ground surface, 0.8–6 dm, sparsely pubescent proximally, trichomes short-stalked and simple, (scattered), 2-rayed, 0.1–0.15 mm, glabrous distally. |
1–4 per caudex branch, arising from margin of rosette near ground surface, 1–3 dm, glabrous throughout. |
Basal leaves | blade oblanceolate, 4–10 mm wide, margins usually dentate, not ciliate, surfaces densely pubescent, trichomes short-stalked, 3- or 4-rayed, 0.1–0.2 mm. |
blade linear-oblanceolate to oblanceolate, 1–3(–5) mm wide, margins entire or minutely toothed, rarely ciliate near petiole base, trichomes (simple), to 0.8 mm, surfaces pubescent or glabrous, trichomes short-stalked, 3–6-rayed, 0.07–0.2 mm. |
Cauline leaves | 7–25, concealing stem proximally; blade auricles 1–4 mm, surfaces of distalmost leaves glabrous. |
4–15, not concealing stem; blade auricles 0.5–2.5 mm, surfaces of distalmost leaves glabrous. |
Racemes | 6–20-flowered, usually unbranched. |
12–40-flowered, usually unbranched. |
Flowers | ascending at anthesis; sepals pubescent; petals dark reddish purple (drying indigo), 7–9 × 1.5–2 mm, glabrous; pollen ellipsoid. |
divaricate to pendent at anthesis; sepals pubescent; petals lavender, 5–6 × ca. 1 mm, glabrous; pollen ellipsoid or spheroid. |
Fruiting pedicels | ascending, usually straight, 5–10 mm, glabrous or pubescent, trichomes spreading, simple. |
reflexed, abruptly recurved near base, 4–8 mm, glabrous. |
Fruits | ascending, not appressed to rachis, not secund, curved or straight, edges parallel, (4–)6–12 cm × 1.7–2.2 mm; valves glabrous; ovules 80–100 per ovary; style 0.2–0.5 mm. |
reflexed to closely pendent, usually appressed to rachis, often secund, straight, edges parallel, 0.3–0.42 cm × 1–1.5 mm; valves glabrous; ovules 46–60 per ovary. |
Seeds | uniseriate, 1.2–1.7 × 0.9–1.2 mm; wing lateral and distal, 0.1–0.2 mm wide. |
uniseriate, 1–1.3 × 0.8–1 mm; wing continuous, 0.05–0.1 mm wide. |
Boechera atrorubens |
Boechera hastatula |
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Phenology | Flowering Apr–May. | Flowering Jun–Jul. |
Habitat | Rocky summits and sandy loam on sagebrush slopes | Igneous rock outcrops |
Elevation | ca. 600 m (ca. 2000 ft) | 1900-2100 m (6200-6900 ft) |
Distribution |
OR; WA
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OR |
Discussion | Boechera atrorubens is often treated as a variety of B. sparsiflora (e.g., R. C. Rollins 1993), it is readily separated from that species by having proximal stems sparsely (versus densely) pubescent with much smaller (0.15 versus 1.5 mm) trichomes. The two taxa rarely grow in proximity and, in areas where they are sympatric, B. atrorubens is further distinguished by its narrower (1.5–2 versus 2–5 mm) petals that are dark reddish purple to indigo (versus lavender or white). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Of conservation concern. Both sexual and apomictic collections of Boechera hastatula have been identified; further study is needed to determine whether they truly are conspecific. The species is known only from Baker and Wallowa counties. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 366. | FNA vol. 7, p. 383. |
Parent taxa | Brassicaceae > tribe Boechereae > Boechera | Brassicaceae > tribe Boechereae > Boechera |
Sibling taxa | ||
Synonyms | Arabis atrorubens, Arabis atriflora, Arabis sparsiflora var. atrorubens | Arabis hastatula |
Name authority | (Suksdorf ex Greene) Windham & Al-Shehbaz: Harvard Pap. Bot. 11: 64. (2006) | (Greene) Al-Shehbaz: Novon 13: 386. (2003) |
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