Flora of North America species comparison

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Draba densifolia

Draba sibirica

dense-leaf Draba, dense-leaf whitlow-grass, Nuttall's Draba, Nuttall's whitlow-grass

Siberian whitlowgrass
Habit Perennials; (cespitose, pulvinate); caudex branched (dense with persistent leaf remains, branches sometimes terminating in sterile rosettes); scapose. Perennials; (stoloniferous); caudex branched (sparsely covered with persistent petiole remains, branches slender, creeping); scapose.
Stems

unbranched, (0.05–)0.2–1(–1.7) dm, usually glabrous, rarely pubescent, trichomes usually simple, 0.3–0.8 mm, and 2–4 (or 5)-rayed, 0.1–0.6 mm, (rarely predominantly simple ones).

(subdecumbent when sterile), unbranched, 0.5–2.5 dm, sparsely to densely hispid, trichomes malpighiaceous, (flowering scapes sparsely pilose proximally with simple trichomes, often glabrous on distal 1/2).
Basal leaves

rosulate;

sessile;

blade linear to oblong or oblanceolate-linear, 0.3–0.9(–1.4) cm × 0.5–1.5(–2) mm, margins entire, (ciliate, trichomes simple, 0.3–1.2 mm), surfaces glabrous or sparsely pubescent, abaxially with short-stalked, 2–4-rayed trichomes, 0.1–0.3 mm (midvein prominent), adaxially rarely with subapical, simple trichomes.

rosulate; petiolate;

blade oblong-lanceolate or oblanceolate, 0.4–2.2 cm × 1–5(–10) mm, margins entire, surfaces often pubescent, sometimes glabrous (except margins), with appressed, malpighiaceous trichomes (these sometimes with 1 or 2 shorter, lateral branches, appearing 3-fid or cross-shaped).
Cauline leaves

0.

0.
Racemes

2–10(–22)-flowered, ebracteate, not or slightly elongated in fruit;

rachis not or slightly flexuous, glabrous or pubescent as stem.

7–20-flowered, ebracteate, considerably elongated in fruit;

rachis not flexuous (straight), glabrous.
Flowers

sepals ovate, 2–3 mm, usually sparsely pubescent, rarely glabrous, (trichomes simple and short-stalked, 2–4-rayed);

petals pale yellow (sometimes fading white), oblanceolate to obovate, 2–5 × 1–1.7(–2) mm;

anthers ovate or oblong, 0.4–0.6 mm.

sepals (erect), oblong or ovate, 2–2.7 mm (lateral pair subsaccate basally), glabrous or abaxially sparsely pilose, (trichomes simple);

petals yellow, narrowly obovate, 4–6 × 2–3 mm, (apex emarginate);

anthers ovate-subcordate, 0.4–0.5 mm.
Fruiting pedicels

divaricate-ascending to ascending (not decurrent basally), straight, (0.7–)1.5–10(–25) mm, usually glabrous, rarely sparsely pubescent, trichomes predominantly simple (0.2–0.7 mm), sometimes 2–4 (or 5)-rayed, (0.1–0.5 mm).

divaricate, straight or curved, (often filiform), 5–18(–23) mm, glabrous.
Fruits

ovoid or ovate-lanceolate, plane (not curved), flattened, (2.5–)3–6(–8) × 2–3 mm;

valves pubescent or puberulent, trichomes simple and short-stalked, 2–5-rayed, 0.1–0.4 mm;

ovules 4–12 per ovary;

style 0.3–0.6(–1) mm.

usually oblong to elliptic, rarely sublinear, plane, flattened, 4–8 × 1.5–2.2 mm;

valves glabrous, (obscurely veined);

ovules 24–30 per ovary;

style 0.5–1 mm.
Seeds

oblong to ovoid, 1.2–2(–2.6) × 0.9–1.2(–1.4) mm.

(brown), ovoid, 0.9–1.2 × 0.5–0.6 mm.
2n

= 36.

= 16.

Draba densifolia

Draba sibirica
Phenology Flowering Jun–Aug. Flowering May–Jul.
Habitat Rock outcrops and talus, rocky knolls, alpine ridges Wet places on rocky slopes
Elevation 800-3700 m (2600-12100 ft) 0-300 m (0-1000 ft)
Distribution
from FNA
AK; CA; ID; NV; OR; UT; WA; WY; AB; BC
[WildflowerSearch map]
[BONAP county map]
from USDA
Greenland; Europe (Russia); Asia (Caucasus, Iran, Russian Far East, Siberia, Turkey, central republics)
[BONAP county map]
Discussion

Draba densifolia is one of the most highly variable North American members of the genus, as evidenced by the extensive synonymy. The species is an apomict (G. A. Mulligan 1976) and it occupies tremendous geographic, edaphic, and altitudinal ranges. In forms corresponding to the type of D. sphaerula, the flowering stems are 2-flowered, and the stems, leaves, and fruiting pedicels are to 5, 1.5, and 0.6 mm, respectively. By contrast, forms comparable to the type of D. caeruleomontana var. piperi have stems, leaves, and fruiting pedicels to 17, 1.3, and 2.5 cm, respectively. Between these remarkable extremes fall all of the other populations of the species.

Draba densifolia is sometimes confused with D. paysonii, which it resembles, in being a cespitose, scapose, and densely pulvinate perennial having narrowly linear or oblong to linear-oblanceolate leaf blades with strongly ciliate margins. It is easily distinguished from the latter by having glabrous adaxial leaf blade surfaces, only sparsely pubescent abaxial surfaces, and often glabrous fruiting pedicels and rachises.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Draba sibirica is one of three species of the genus in North America exhibiting malpighiaceous trichomes. It is easily distinguished from others (D. malpighiacea and some plants of D. spectabilis) by a complete absence of cauline leaves. It is found in the flora area in northeastern Greenland.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 7, p. 306. FNA vol. 7, p. 337.
Parent taxa Brassicaceae > tribe Arabideae > Draba Brassicaceae > tribe Arabideae > Draba
Sibling taxa
D. abajoensis, D. albertina, D. aleutica, D. alpina, D. aprica, D. arabisans, D. arctica, D. arctogena, D. argyrea, D. arida, D. asprella, D. asterophora, D. aurea, D. aureola, D. bifurcata, D. borealis, D. brachycarpa, D. brachystylis, D. breweri, D. burkei, D. californica, D. cana, D. carnosula, D. chamissonis, D. cinerea, D. corrugata, D. corymbosa, D. crassa, D. crassifolia, D. cruciata, D. cuneifolia, D. cusickii, D. cyclomorpha, D. daviesiae, D. exunguiculata, D. fladnizensis, D. glabella, D. globosa, D. graminea, D. grandis, D. grayana, D. heilii, D. helleriana, D. hitchcockii, D. howellii, D. incana, D. incerta, D. incrassata, D. inexpectata, D. jaegeri, D. juvenilis, D. kassii, D. kluanei, D. lactea, D. lemmonii, D. lonchocarpa, D. longisquamosa, D. macounii, D. maguirei, D. malpighiacea, D. micropetala, D. mogollonica, D. monoensis, D. mulliganii, D. murrayi, D. nemorosa, D. nivalis, D. norvegica, D. novolympica, D. oblongata, D. ogilviensis, D. oligosperma, D. oreibata, D. oxycarpa, D. palanderiana, D. pauciflora, D. paucifructa, D. paysonii, D. pectinipila, D. pedicellata, D. pennellii, D. petrophila, D. pilosa, D. platycarpa, D. porsildii, D. praealta, D. pterosperma, D. ramosissima, D. ramulosa, D. rectifructa, D. reptans, D. ruaxes, D. santaquinensis, D. saxosa, D. scotteri, D. serpentina, D. sharsmithii, D. sibirica, D. sierrae, D. simmonsii, D. smithii, D. sobolifera, D. spectabilis, D. sphaerocarpa, D. sphaeroides, D. standleyi, D. stenoloba, D. stenopetala, D. streptobrachia, D. streptocarpa, D. subalpina, D. subcapitata, D. subumbellata, D. trichocarpa, D. ventosa, D. verna, D. viridis, D. weberi, D. yukonensis, D. zionensis
D. abajoensis, D. albertina, D. aleutica, D. alpina, D. aprica, D. arabisans, D. arctica, D. arctogena, D. argyrea, D. arida, D. asprella, D. asterophora, D. aurea, D. aureola, D. bifurcata, D. borealis, D. brachycarpa, D. brachystylis, D. breweri, D. burkei, D. californica, D. cana, D. carnosula, D. chamissonis, D. cinerea, D. corrugata, D. corymbosa, D. crassa, D. crassifolia, D. cruciata, D. cuneifolia, D. cusickii, D. cyclomorpha, D. daviesiae, D. densifolia, D. exunguiculata, D. fladnizensis, D. glabella, D. globosa, D. graminea, D. grandis, D. grayana, D. heilii, D. helleriana, D. hitchcockii, D. howellii, D. incana, D. incerta, D. incrassata, D. inexpectata, D. jaegeri, D. juvenilis, D. kassii, D. kluanei, D. lactea, D. lemmonii, D. lonchocarpa, D. longisquamosa, D. macounii, D. maguirei, D. malpighiacea, D. micropetala, D. mogollonica, D. monoensis, D. mulliganii, D. murrayi, D. nemorosa, D. nivalis, D. norvegica, D. novolympica, D. oblongata, D. ogilviensis, D. oligosperma, D. oreibata, D. oxycarpa, D. palanderiana, D. pauciflora, D. paucifructa, D. paysonii, D. pectinipila, D. pedicellata, D. pennellii, D. petrophila, D. pilosa, D. platycarpa, D. porsildii, D. praealta, D. pterosperma, D. ramosissima, D. ramulosa, D. rectifructa, D. reptans, D. ruaxes, D. santaquinensis, D. saxosa, D. scotteri, D. serpentina, D. sharsmithii, D. sierrae, D. simmonsii, D. smithii, D. sobolifera, D. spectabilis, D. sphaerocarpa, D. sphaeroides, D. standleyi, D. stenoloba, D. stenopetala, D. streptobrachia, D. streptocarpa, D. subalpina, D. subcapitata, D. subumbellata, D. trichocarpa, D. ventosa, D. verna, D. viridis, D. weberi, D. yukonensis, D. zionensis
Synonyms D. caeruleomontana, D. caeruleomontana var. piperi, D. glacialis var. pectinata, D. globosa var. sphaerula, D. mulfordiae, D. nelsonii, D. oligosperma var. pectinata, D. pectinata, D. sphaerula Lepidium sibiricum, D. gmelinii, D. repens, D. sibirica subsp. arctica
Name authority Nuttall: in J. Torrey and A. Gray, Fl. N. Amer. 1: 104. (1838) (Pallas) Thellung: Neue Denkschr. Schweiz. Naturf. Ges. 41: 318. (1907)
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Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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