Draba cana |
Draba viridis |
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Brewer's Draba, canescent Draba, canescent whitlow-mustard, cushion Draba, hoary Draba, hoary whitlow-grass, lance-leaf Draba, lance-leaf whitlow-grass |
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Habit | Perennials; caudex simple or branched (branches short); not scapose. | Perennials; (long-lived, cespitose); caudex simple or branched (densely covered with persistent petioles); not scapose. |
Stems | unbranched or branched distally, (0.6–)1–3(–3.8) dm, pubescent throughout, trichomes simple, 0.5–1mm, with 4–10-rayed ones, 0.05–0.2 mm (mostly branched on basal parts). |
unbranched or branched, 0.35–3 dm, pubescent throughout, trichomes simple, 0.2–0.8 mm, with short-stalked to subsessile, cruciform ones, 0.05–0.2 mm. |
Basal leaves | rosulate; petiolate; petiole ciliate throughout; blade linear to oblanceolate or oblong, (0.5–)0.8–2(–3.5) cm × 1.5–4(–11) mm, margins entire or dentate, (base and apex ciliate, trichomes simple, 0.3–0.8 mm), surfaces pubescent with short-stalked, 4–12-rayed trichomes, 0.1–0.3 mm. |
rosulate; petiolate; petiole ciliate, (trichomes simple, 0.4–1 mm); blade oblanceolate, 1–6 cm × 2–6 mm, margins usually entire, rarely denticulate, surfaces pubescent with stalked, cruciform trichomes, 0.1–0.5 mm. |
Cauline leaves | 3–10(–17), (not overlapping); sessile; blade lanceolate to ovate or oblong, margins entire or dentate, surfaces pubescent as basal (adaxially with simple and forked trichomes near blade base). |
5–16; sessile; blade ovate to lanceolate or oblong, margins entire or denticulate, surfaces pubescent as basal. |
Racemes | (10–)15–47(–63)-flowered, basally bracteate, often considerably elongated in fruit; rachis not flexuous, densely pubescent, trichomes 4–10-rayed (0.05–0.2 mm), and fewer simple ones. |
11–28-flowered, ebracteate, elongated in fruit; rachis not flexuous, pubescent as stem. |
Flowers | sepals (green or lavender), oblong to ovate, 1.5–2 mm, pubescent, (trichomes simple and few-rayed); petals white, oblanceolate to spatulate, 2.3–3.7(–4.5) × 0.7–1.7 mm; anthers ovate, 0.1–0.2 mm. |
sepals oblong, 2–3 mm, pubescent, (trichomes simple and 2-rayed); petals yellow, oblanceolate, 3.5–5 × 1–1.5 mm; anthers ovate, 0.5–0.6 mm. |
Fruiting pedicels | suberect or ascending, straight, 2–5(–10) mm, pubescent as rachis. |
divaricate, straight, 4–7 mm, pubescent throughout, trichomes simple (0.1–0.4 mm) and subsessile, 2–4-rayed (0.03–0.25 mm). |
Fruits | (subappressed to rachis), linear-lanceolate to linear or, rarely, ovate-oblong, slightly twisted or plane, flattened, (5–)6–11 × 1.5–2(–2.5) mm; valves pubescent, trichomes short-stalked, 3–7-rayed, 0.05–0.3 mm; ovules 28–48 per ovary; style 0.1–0.6 mm. |
lanceolate to ovate, often plane, flattened, 3.5–8 × 2–3 mm; valves pubescent, trichomes (vertical), simple and 2–4-rayed, (0.1–)0.3–0.8 mm; ovules 12–20 per ovary; style (1.5–)2–3 mm. |
Seeds | ovoid, 0.5–0.7(–0.9) × 0.3–0.5 mm. |
ovoid, 1.2–1.5 × 0.7–0.9 mm. |
2n | = 32. |
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Draba cana |
Draba viridis |
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Phenology | Flowering (May-)Jun–Aug. | Flowering Aug–Sep. |
Habitat | Rock outcrops and talus, open prairie benchlands, roadsides, meadows, alpine tundra | Open stands of pines |
Elevation | 0-4100 m (0-13500 ft) | ca. 2600 m (ca. 8500 ft) |
Distribution |
AK; CA; CO; ID; ME; MI; MT; NH; NM; NV; SD; UT; VT; WA; WI; WY; AB; BC; MB; NB; NF; NT; ON; QC; SK; YT; Greenland
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AZ; Mexico (Sonora) |
Discussion | The limits of Draba cana have long been confused, and the species was treated as a synonym of the Himalayan D. lanceolata Royle (M. L. Fernald 1934; C. L. Hitchcock 1941) or as a variety of the western North American D. breweri (R. C. Rollins 1993). However, G. A. Mulligan (1971) clearly demonstrated that all three are distinct and should be maintained. Some Utah plants corresponding to the type of D. valida have shorter and wider oblong-ovate fruits. In all other aspects, they are indistinguishable from D. cana. Additional studies are needed to establish whether such plants should be formally recognized. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Of conservation concern. Draba viridis has been reported from the Huachuca and Santa Catalina mountains in southern Arizona, and the adjacent San Jose Mountains in Sonora, Mexico. It was reduced to a variety of D. petrophila by Hitchcock and a form of D. helleriana by O. E. Schulz, but is easily separated from both (I. A. Al-Shehbaz and M. D. Windham 2007). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 298. | FNA vol. 7, p. 345. |
Parent taxa | Brassicaceae > tribe Arabideae > Draba | Brassicaceae > tribe Arabideae > Draba |
Sibling taxa | ||
Synonyms | D. breweri var. cana, D. valida | D. petrophila var. viridis |
Name authority | Rydberg: Bull. Torrey Bot. Club 29: 241. (1902) | A. Heller: Muhlenbergia 1: 27. (1901) |
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