Flora of North America species comparison

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Draba stenoloba

Draba pilosa

Alaska Draba, Alaska whitlow-grass
Habit Biennials or perennials; (short-lived, not cespitose); caudex simple (not fleshy); scapose. Perennials; (not stoloniferous); caudex branched (covered with persistent, dry leaves and midveins); scapose.
Stems

often unbranched, (0.2–)0.4–3(–3.4) dm, pubescent proximally, usually glabrous distally, rarely sparsely pubescent, trichomes short-stalked, 2–4-rayed, 0.1–0.4(–0.5) mm.

unbranched, 0.4–1.7 dm, glabrous or pubescent, trichomes simple, 0.2–0.9 mm, and fewer, 2–4-rayed, 0.1–0.6 mm.
Basal leaves

rosulate;

petiole (obscure), margin ciliate, (trichomes simple, 0.2–0.4 mm);

blade oblanceolate to obovate, 0.4–2.6(–3.1) cm × 1.5–7(–10) mm, margins entire or denticulate, (ciliate as petiole), surfaces pubescent, abaxially with short-stalked, 3- or 4-rayed trichomes, 0.1–0.5 mm, adaxially with simple and stalked, 2–4-rayed trichomes, 0.1–0.5 mm.

(imbricate); rosulate; petiolate;

petiole (base thickened), ciliate throughout;

blade linear to linear-oblanceolate, 0.5–1.5(–2.2) cm × 1–2.5(–4) mm, margins entire (thickened, ciliate, trichomes simple and 2-rayed, to 1.1 mm), surfaces pubescent, abaxially with simple trichomes, 0.3–1 mm, and 2–4-rayed ones, 0.1–0.5 mm, adaxially similar, or with only simple trichomes, (midvein prominent, thickened).
Cauline leaves

(0 or) 1 or 2 (3 or 4);

sessile;

blade elliptic to lanceolate or ovate, margins toothed, surfaces pubescent, abaxially with short-stalked 3- or 4-rayed trichomes, adaxially with simple and short-stalked, 2–4-rayed trichomes.

0.
Racemes

(2–)4–10(–15)-flowered, ebracteate, elongated in fruit;

rachis not flexuous, usually glabrous, rarely sparsely pubescent.

(2–)4–12-flowered, ebracteate, usually elongated in fruit;

rachis not flexuous, glabrous or pubescent as stem.
Flowers

(chasmogamous, petaliferous);

sepals (green or purplish), oblong, 1.5–2.5 mm, glabrous or pubescent, (trichomes simple);

petals yellow, oblanceolate, 2.5–3.5 × 0.6–1 mm;

anthers ovate, 0.25–0.4 mm.

sepals ovate, 2–3.5 mm, pubescent, (trichomes simple and short-stalked, 2-rayed);

petals pale to bright yellow, obovate, 3.5–6 × 2–3.5 mm;

anthers ovate, 0.4–0.5 mm.
Fruiting pedicels

horizontal to divaricate-ascending, straight, 3–14(–19) mm (subequaling or shorter than fruit), usually glabrous, rarely pubescent, trichomes 2–4-rayed.

divaricate-ascending, usually straight, rarely curved upward, 6–13 mm, glabrous or pubescent as stem.
Fruits

linear or, rarely, linear-elliptic, plane, flattened, (8–)10–17(–20) × 1.5–2 mm;

valves usually glabrous, rarely sparsely puberulent, trichomes simple;

ovules 24–36 per ovary;

style 0.01–0.15 mm.

elliptic to lanceolate, 5–11 × 3–4 mm, plane, flattened;

valves glabrous or puberulent with simple and short-stalked, 2-rayed trichomes, 0.07–0.3 mm;

ovules 12–20 per ovary;

style 0.4–0.9 mm (stigma about as wide as style).
Seeds

ovoid, 0.9–1 × 0.5–0.6 mm.

ovoid, 1.2–1.4 × 0.8–1 mm.
2n

= 40.

Draba stenoloba

Draba pilosa
Phenology Flowering Jun–Jul. Flowering Jul–Aug.
Habitat Grassy knolls, glacial moraines and creek banks, mesic meadows, alpine thickets Dry gravelly slopes, sandy places, wet tundra
Elevation 600-2300 m (2000-7500 ft) 0-1300 m (0-4300 ft)
Distribution
from FNA
AK; OR; WA; AB; BC; YT
[WildflowerSearch map]
[BONAP county map]
from FNA
AK; NT; NU; YT; e Asia (ne Russian Far East, n Siberia)
[BONAP county map]
Discussion

Draba stenoloba is occasionally confused with D. albertina, but is easily recognized by having exclusively 2–4-rayed (versus mostly simple) trichomes on stems proximally. It is rarely encountered and apparently confined to the Pacific Northwest. In contrast, D. albertina is common and widespread in the mountains of western North America.

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

O. E. Schulz (1927) reduced Draba pilosa to a variety of the decaploid D. alpina and cited North American collections. The former species was not listed by C. L. Hitchcock (1941) or R. C. Rollins (1993). From D. alpina, D. pilosa is easily distinguished by having strongly thickened and persistent (versus not thickened) midveins and margins, and usually narrower leaf blades [1–2.5(–5) versus 2.5–6(–9) mm wide].

As recognized herein, Draba pilosa is broadly circumscribed to include perhaps two or three closely related taxa. All are scapose plants with large, yellow flowers and prominent, persistent midveins and petioles. Some Alaskan forms (e.g., Parker 7596, ALA), which grow in moist heath habitats, have leaves 3–5 mm wide, whereas the majority have narrower leaf blades rarely reaching 2.5 mm in width. Most plants assigned to this species have leaves with exclusively simple trichomes and often glabrous scapes. Others (e.g., Chesemore & Davies 13, Murray 3371, Parker & Batten 8954, all at ALA) have leaf blade surfaces and scapes with 2–4-rayed trichomes and blade margins ciliate with simple trichomes. One collection (Walker s.n., ALA) has a mixture of plants of both trichome types but no intermediates were found. Detailed molecular and cytological studies are needed on this complex to determine if more than one taxon is represented.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 7, p. 340. FNA vol. 7, p. 330.
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. 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. sibirica, D. sierrae, D. simmonsii, D. smithii, D. sobolifera, D. spectabilis, D. sphaerocarpa, D. sphaeroides, D. standleyi, 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. 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
Synonyms D. acinacis, D. hirta var. siliquosa, D. macouniana, D. nemorosa var. stenoloba, D. nitida var. praelonga, D. oligantha, D. stenoloba var. oligantha D. alpina var. pilosa, D. aspera
Name authority Ledebour: Fl. Ross. 1: 154. (1841) Adams ex de Candolle: in A. P. de Candolle, Syst. Nat. 2: 336. (1821)
Web links 
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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