Boechera collinsii |
Boechera serotina |
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collin's suncress, Collins' rockcress |
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Habit | Perennials; usually short-lived; sexual; caudex not woody. | Biennials; short-lived; sexual; caudex not evident. |
Stems | usually 1 per caudex branch, arising from center of rosette near ground surface, (1.5–)2.5–8 dm, densely pubescent proximally, trichomes simple and short-stalked, 2-rayed, to 1 mm, sparsely pubescent or glabrous distally. |
usually 1 per plant, arising from center of rosette near ground surface, 4–10 dm, glabrous throughout. |
Basal leaves | blade oblanceolate, 1–7 mm wide, margins entire or dentate, ciliate along petiole, trichomes (simple), to 0.7 mm, surfaces moderately to densely pubescent, trichomes short-stalked, 5–8-rayed, 0.15–0.4 mm. |
blade obovate to oblanceolate, 5–20 mm wide, margins dentate, not ciliate, surfaces glabrous or subapically puberulent, trichomes simple, 0.1–0.2 mm. |
Cauline leaves | (8–)15–40, concealing stem proximally; blade auricles 1–3 mm, surfaces of distalmost leaves usually sparsely pubescent. |
30–80, not concealing stem; blade auricles absent, surfaces of distalmost leaves glabrous. |
Racemes | (15–)30–90-flowered, usually unbranched. |
70–150-flowered, multi-branched. |
Flowers | descending to pendent at anthesis; sepals pubescent; petals usually white, rarely lavender, 4–6 × 0.8–1.5 mm, glabrous; pollen ellipsoid. |
divaricate-ascending at anthesis; sepals glabrous; petals white, 2.8–4 × 0.6–1 mm, glabrous; pollen ellipsoid. |
Fruiting pedicels | reflexed, abruptly recurved at base, otherwise straight, 4–13 mm, glabrous or sparsely pubescent, trichomes usually simple. |
divaricate-ascending to horizontal, straight or gently recurved, 6–15 mm, glabrous. |
Fruits | strongly reflexed, usually appressed to rachis, rarely somewhat secund, straight, edges parallel, 3.5–6 cm × 0.9–1.5 mm; valves glabrous; ovules 70–126 per ovary; style 0.2–0.5 mm. |
divaricate-ascending to widely pendent, not appressed to rachis, not secund, straight or slightly curved, edges parallel, 4.3–7.9 cm × 1.5–1.8 mm; valves glabrous; ovules 30–42 per ovary; style 0.1–0.2 mm. |
Seeds | uniseriate, 1–1.4 × 0.8–1 mm; wing continuous (rarely absent), to 0.1 mm wide. |
uniseriate, 1.2–1.7 × 0.7–1 mm; wing continuous or, sometimes, distal (rarely absent), 0.1–0.2 mm wide. |
Flowering | Jul–Sep. |
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Shale | barrens and wooded slopes of crumbling shale; of conservation concern; 100–500 m; Va., W.Va. |
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2n | = 14. |
= 14. |
Boechera collinsii |
Boechera serotina |
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Phenology | Flowering May–Jun. | Flowering Jul–Sep. |
Habitat | Rocky and gravelly hillsides, prairies, open woods, floodplains | Shale barrens and wooded slopes of crumbling shale |
Elevation | 600-1400 m (2000-4600 ft) | 100-500 m (300-1600 ft) |
Distribution |
ID; MN; MT; ND; NE; SD; WY; AB; MB; QC; SK
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VA; WV |
Discussion | Though often treated as a variety of Arabis (Boechera) holboellii (e.g., R. C. Rollins 1993; G. A. Mulligan 1996), B. collinsii is easily distinguished from that species by having simple and 2-rayed (versus 4–8-rayed) trichomes proximally on stems, and narrower (0.9–1.5 versus 2–2.5 mm) usually non-secund fruits. The two taxa also show allopatric distributions, with B. collinsii found on the North American continent (usually east of the Rocky Mountains) and B. holboellii apparently confined to Greenland. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
boechera serotina is unique among members of the genus in its highly branched inflorescences and late (summer–fall) anthesis. it is in the center for plant conservation’s national collection of endangered plants of conservation concern (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 370. | FNA vol. 7, p. 405. |
Parent taxa | Brassicaceae > tribe Boechereae > Boechera | Brassicaceae > tribe Boechereae > Boechera |
Sibling taxa | ||
Synonyms | Arabis collinsii, Arabis holboellii var. collinsii, Arabis retrofracta var. collinsii | Arabis serotina |
Name authority | (Fernald) Á. Löve & D. Löve: Taxon 31: 125. (1982) | (E. S. Steele) Windham & Al-Shehbaz: Harvard Pap. Bot. 12: 249. (2007) |
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