Draba aurea |
Draba nemorosa |
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golden Draba, golden Draba whitlow-grass, golden whitlow-grass, twisted-pod Draba |
woodland Draba, woodland whitlow-grass, woods Draba, woods whitlow-grass, yellow whitlow-grass |
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Habit | Perennials; (not cespitose); caudex simple or branched; not scapose. | Annuals; not scapose. |
Stems | sometimes branched distally, (0.5–) 1–3.5(–5.2) dm, pubescent throughout, trichomes simple (non-crisped), 0.4–1.3 mm, and 3–6-rayed ones, 0.1–0.5 mm. |
unbranched or branched proximally, (0.3–)0.6–4.5(–6) dm, densely pubescent proximally, glabrous distally, trichomes simple, 0.5–1.3 mm, and stalked, 2–4-rayed, 0.1–0.5 mm. |
Basal leaves | rosulate; petiolate; petiole (distinct or obscure) ciliate, (trichomes simple, to 0.8 mm); blade oblanceolate to obovate, (0.4–)1–3.7(–5) cm × (1–)2–7(–10) mm, margins entire or denticulate, surfaces pubescent, trichomes stalked, (2–)4–7 (or 8)-rayed, 0.2–0.5(–0.6) mm. |
rosulate or not, petiolate; petiole ciliate throughout; blade oblong-obovate or oblanceolate, (0.4–)1–3.5(–5) cm × (2–)5–15(–20) mm, margins usually dentate to denticulate, rarely subentire, surfaces sparsely to densely pubescent with stalked, 2- or 3-rayed, and cruciform trichomes, 0.1–0.5 mm. |
Cauline leaves | 5–20(–26); sessile; blade oblong to lanceolate or ovate, margins entire or dentate, surfaces pubescent as basal, sometimes adaxially with simple trichomes. |
4–12(–15); sessile; blade broadly ovate to oblong, margins dentate or denticulate, surfaces pubescent, abaxially as basal, adaxially with primarily simple, and 2- or 3-rayed trichomes. |
Racemes | (10–)18–52(–72)-flowered, usually bracteate on proximalmost 1–12(–17) flowers, rarely ebracteate, elongated in fruit; rachis not flexuous, pubescent as stem. |
(10–)18–60(–92)-flowered, ebracteate, considerably elongated in fruit; rachis not flexuous (straight), glabrous. |
Flowers | sepals (green or yellowish), oblong, 2.2–3 mm, pubescent, (trichomes simple and branched); petals yellow, oblanceolate, 3.5–5 × 1.5–2.5 mm; anthers ovate, 0.4–0.5 mm. |
sepals ovate, (0.7–)0.9–1.6 mm, sparsely pubescent, (trichomes simple); petals yellow, spatulate to oblanceolate, (1.2–)1.7–2.2(–2.5) × (0.4–)0.6–1 mm, (deeply notched); anthers broadly ovate to subreniform, 0.1–0.2 mm. |
Fruiting pedicels | divaricate-ascending to ascending or suberect, straight, 3–13(–20) mm, pubescent as stem. |
divaricate, straight, 7–28(–35) mm [(1.5–)2–7 times longer than fruit], glabrous. |
Fruits | (often subappressed to rachis), lanceolate to linear-lanceolate or narrowly oblong, slightly twisted or plane, flattened, (6–)9–14(–17) × 2–3.5 mm; valves pubescent, trichomes simple and short-stalked, 2–4-rayed, 0.05–0.3 mm; ovules 28–38(–44) per ovary; style 0.5–1.2(–1.5) mm. |
oblong to elliptic or, rarely, oblong-oblanceolate, plane, slightly flattened, (3–)5–8 (–10) × 1.5–2.5 mm; valves glabrous or puberulent, trichomes simple, antrorse, 0.05–0.2 mm; ovules (30–)36–60(–72) per ovary; style 0.01–0.1 mm. |
Seeds | oblong, 0.9–1.3 × 0.5–0.7 mm. |
ovoid, 0.5–0.7(–0.8) × 0.3–0.4(–0.5) mm. |
2n | = 74. |
= 16. |
Draba aurea |
Draba nemorosa |
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Phenology | Flowering Jun–Aug. | Flowering Apr–Jul. |
Habitat | Rock outcrops, talus, damp gullies and meadows, subalpine conifer woodlands, alpine slopes and turf, tundra, road banks, river gravel | Rock outcrops, open wooded slopes, meadows and prairies, stream banks, roadsides, disturbed gravelly grounds, waste places |
Elevation | (0-)700-4200 m ((0-)2300-13800 ft) | 0-2700 m (0-8900 ft) |
Distribution |
AK; AZ; CO; ID; MT; NM; NV; SD; UT; WA; WY; AB; BC; MB; NF; NT; NU; ON; QC; SK; YT; Greenland
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AK; CA; CO; IA; ID; MI; MN; MT; ND; NE; NV; OR; SD; UT; WA; WI; WY; AB; BC; MB; NT; NU; ON; QC; SK; YT; Europe; Asia [Introduced in North America; introduced also in Australia]
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Discussion | Draba aurea is extremely variable in plant size, number of cauline leaves, number of bracteate flowers, style length, and fruit size, shape, orientation, twisting, and indumentum. Much of the variation in the number of bracts, style length, fruit twisting, and growth habit occurs in Greenland, where the type specimen was collected and where the species is found near sea level. The highly deviant chromosome counts (e.g., 2n = 40 + 1, 64, 82) listed by R. C. Rollins (1993) and S. I. Warwick and I. A. Al-Shehbaz (2006) are mostly unvouchered and have to be disregarded; counts of 2n = ca. 80 have been re-assigned to Draba glabella. Published (G. A. Mulligan 2002) and unpublished counts made by Mulligan and M. D. Windham from Alaska, British Columbia, Colorado, Quebec, Utah, and Yukon indicate that the most common chromosome number of D. aurea is 2n = 74 (or 72). This suggests that the species is an allopolyploid (hexaploid or higher), incorporating genomes from both euploid and aneuploid lineages (M. A. Beilstein and Windham 2003). Detailed cytological and molecular studies are much needed to fully understand this widely distributed and highly variable species. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Source | FNA vol. 7, p. 294. | FNA vol. 7, p. 321. |
Parent taxa | Brassicaceae > tribe Arabideae > Draba | Brassicaceae > tribe Arabideae > Draba |
Sibling taxa | ||
Synonyms | D. aurea var. aureiformis, D. aurea var. leiocarpa, D. aurea var. luteola, D. aureiformis, D. aureiformis var. leiocarpa, D. bakeri, D. decumbens, D. henneana var. maccallae, D. luteola, D. luteola var. minganensis, D. maccallae, D. minganensis, D. surculifera, D. uber | D. dictyota, D. nemoralis, D. nemorosa var. brevisilicula, D. nemorosa var. hebecarpa, D. nemorosa var. leiocarpa, Tomostima nemorosa |
Name authority | Vahl ex Hornemann: Fors. Oecon. Plantel. ed. 2, 599. (1806) | Linnaeus: Sp. Pl. 2: 643. (1753) |
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