Draba

Linnaeus
Sp. Pl. 2: 642. 1753.
Etymology: Greek drabe, acrid, for taste of mustard plant
Synonyms: Abdra Greene Erophila de Candolle Nesodraba Greene Tomostima Rafinesque
Treatment appears in FNA Volume 7. Treatment on page 269. Mentioned on page 234, 235, 236, 237, 238, 240, 241, 243, 270, 271, 290, 310, 312, 314.

Annuals, biennials, or perennials [subshrubs]; (caudex simple or branched); scapose or not; glabrous or pubescent, trichomes stalked or sessile, simple, forked, cruciform, stellate, malpighiaceous, or dendritic, often more than 1 kind present. Stems usually erect to ascending, sometimes decumbent or prostrate, unbranched or branched (usually distally). Leaves usually basal and cauline, sometimes cauline absent; petiolate or sessile; basal usually rosulate, usually petiolate, rarely sessile, blade margins usually entire or toothed, rarely pinnately lobed; cauline (when present), petiolate or sessile, blade (base cuneate [auriculate]), margins entire or dentate. Racemes (often corymbose, sometimes bracteate), elongated or not in fruit. Fruiting pedicels (proximalmost) erect or ascending to divaricate, slender. Flowers: sepals (rarely persistent), erect, ascending, or, rarely, spreading, ovate or oblong [elliptic], lateral pair not saccate or subsaccate basally; petals (erect or ascending to patent), yellow, white, pink, purple, or orange [red], obovate, spatulate, oblanceolate, or linear [orbicular, oblong], (longer than or, rarely, shorter than sepals), claw obscurely to well-differentiated from blade, (apex obtuse, rounded, notched, or, rarely, deeply 2-lobed); stamens slightly to strongly tetradynamous; filaments dilated or not basally, (glabrous); anthers ovate or oblong, (not apiculate); nectar glands (1, 2, or 4), distinct or confluent, subtending bases of stamens, median glands present or absent. Fruits silicles or siliques, sessile, ovate, lanceolate, elliptic, oblong, linear, suborbicular, ovoid, or subglobose, plane or spirally twisted, smooth, (not keeled, unappendaged), usually latiseptate, rarely terete; valves (papery), each with distinct or obscure midvein and lateral veins, glabrous or pubescent; replum rounded; septum complete; ovules 4–70(–88) per ovary; style obsolete or distinct; stigma capitate. Seeds biseriate, oblong, ovate, or orbicular, usually flattened (slightly flattened in D. aleutica, D. verna), usually not winged (winged in D. asterophora, D. brachycarpa, D. carnosula, D. pterosperma); seed coat (minutely reticulate), not mucilaginous when wetted; cotyledons accumbent. x = 6–12.

Distribution

North America, Mexico, South America (Andes, Colombia to Patagonia), Europe, Asia, nw Africa, alpine and boreal, rarely in temperate and low-elevation areas of North America and Eurasia.

Discussion

Species ca. 380 (121 in the flora).

Draba, the largest genus in Brassicaceae, is a well-defined, monophyletic, and complex group represented by native species on all continents except Australia and Antarctica. It is poorly developed in Africa. The four centers of highest diversity include western North America, subarctic regions, Himalaya, and high Andes.

The infrageneric classification of Draba is problematic, and preliminary molecular studies (M. Koch and I. A. Al-Shehbaz 2002) do not support the circumscriptions of most of the 17 sections recognized by O. E. Schulz (1927, 1936). A. I. Tolmatchew (1939, 1975) recognized representatives of 29 series occurring within the former Soviet Union, and his classification is far more practical that Schulz’s, though it covers only a small portion of the genus. An overall comprehensive infrageneric taxonomy of Draba is needed.

Much of the complexity within Draba is attributed to hybridization, disploidy, polyploidy, and apomixis; the interested reader should consult E. Ekman (1932b), T. W. Böcher (1966), C. Brochmann (1992, 1992b, 1993), Brochmann and R. Elven (1992), Brochmann et al. (1992, 1992b, 1992c, 1992d, 1993), G. A. Mulligan (1970, 1971, 1971b, 1972, 1974, 1975, 1976), Mulligan and J. N. Findlay (1970), and M. D. Windham (2000, 2004). Except for the results of some studies (e.g., Mulligan and Findlay; Brochmann et al. 1992d; Brochmann 1993; H. H. Grundt et al. 2005), little is known about the reproductive biology of Draba species. The polyphyletic origins of some species (e.g., D. cacuminum, D. corymbosa, D. lactea) have been well-documented (Brochmann et al. 1992b, 1992c; Grundt et al. 2004).

Knowledge of chromosome numbers, combined with a critical study of morphology, is essential in the delimitation of Draba species and in understanding their origin. In addition to the works by T. W. Böcher, C. Brochmann, H. H. Grundt, G. A. Mulligan, and M. D. Windham cited above, those by O. Heilborn (1927) and G. Knaben (1966) also are pertinent. Although the base chromosome number in the genus ranges from six to twelve, the majority of the species (ca. 67%) are based on eight, as compiled from S. I. Warwick and I. A. Al-Shehbaz (2006). The highest chromosome number in the genus, 2n = 144 (18-ploid), was reported by Mulligan (1974b) for D. corymbosa, and a complex, intraspecific disploid series (see below) was documented in D. verna (Ø. Winge 1940).

Although Erophila is recognized in recent floras as distinct from Draba, the sole characteristic on which it is based (petal apex deeply 2-fid versus emarginate to entire in Draba) is unreliable, and it is well-nested within the larger and highly diversified Draba (M. Koch and I. A. Al-Shehbaz 2002).

Because some superficially similar species of Draba grow sympatrically, extra care must be taken in recording flower color and in collecting voucher material for cytological or molecular studies. Cases in point are Thompson & Thompson 578a (DAO), a collection that consists of four species (see 2. D. albertina), and Bruggeman 41 (DAO), one that includes D. fladnizensis, D. lactea, and D. nivalis.

The number of ovules per ovary is taxonomically important in Draba, but this is rather difficult to determine in the ovary. Counting total number of aborted ovules plus mature seeds per fruit should determine the overall ovule number. The use of seed number per fruit often is unreliable because tremendous variation can be found on the same plant as a result of the failure of some ovules to develop into mature seeds. The number of flowers is counted from the main raceme of a plant with branched stems, the length of style is measured from mature fruits, and the size of basal leaves is taken from the largest leaves of the rosette. In order to accurately determine a given collection to species, complete specimens with flowers and mature fruits are needed. Finally, although most authors of this account prefer to use the subspecific rather the varietal rank, no attempt was made here to enforce the choice of either; no new combinations have been made.

Lower Taxa

Draba abajoensis, Draba albertina, Draba aleutica, Draba alpina, Draba aprica, Draba arabisans, Draba arctica, Draba arctogena, Draba argyrea, Draba arida, Draba asprella, Draba asterophora, Draba aurea, Draba aureola, Draba bifurcata, Draba borealis, Draba brachycarpa, Draba brachystylis, Draba breweri, Draba burkei, Draba californica, Draba cana, Draba carnosula, Draba chamissonis, Draba cinerea, Draba corrugata, Draba corymbosa, Draba crassa, Draba crassifolia, Draba cruciata, Draba cuneifolia, Draba cusickii, Draba cyclomorpha, Draba daviesiae, Draba densifolia, Draba exunguiculata, Draba fladnizensis, Draba glabella, Draba globosa, Draba graminea, Draba grandis, Draba grayana, Draba heilii, Draba helleriana, Draba hitchcockii, Draba howellii, Draba incana, Draba incerta, Draba incrassata, Draba inexpectata, Draba jaegeri, Draba juvenilis, Draba kassii, Draba kluanei, Draba lactea, Draba lemmonii, Draba lonchocarpa, Draba longisquamosa, Draba macounii, Draba maguirei, Draba malpighiacea, Draba micropetala, Draba mogollonica, Draba monoensis, Draba mulliganii, Draba murrayi, Draba nemorosa, Draba nivalis, Draba norvegica, Draba novolympica, Draba oblongata, Draba ogilviensis, Draba oligosperma, Draba oreibata, Draba oxycarpa, Draba palanderiana, Draba pauciflora, Draba paucifructa, Draba paysonii, Draba pectinipila, Draba pedicellata, Draba pennellii, Draba petrophila, Draba pilosa, Draba platycarpa, Draba porsildii, Draba praealta, Draba pterosperma, Draba ramosissima, Draba ramulosa, Draba rectifructa, Draba reptans, Draba ruaxes, Draba santaquinensis, Draba saxosa, Draba scotteri, Draba serpentina, Draba sharsmithii, Draba sibirica, Draba sierrae, Draba simmonsii, Draba smithii, Draba sobolifera, Draba spectabilis, Draba sphaerocarpa, Draba sphaeroides, Draba standleyi, Draba stenoloba, Draba stenopetala, Draba streptobrachia, Draba streptocarpa, Draba subalpina, Draba subcapitata, Draba subumbellata, Draba trichocarpa, Draba ventosa, Draba verna, Draba viridis, Draba weberi, Draba yukonensis, Draba zionensis

Keys

Key to Species Groups of Draba

1 Annuals or biennials, without caudex or stolons, not pulvinate, not cespitose Group 1
1 Perennials, with caudex or, rarely, stolons, sometimes pulvinate or cespitose > 2
2 Cauline leaves of flowering stems 1+ > 3
2 Cauline leaves of flowering stems 0 > 6
3 Abaxial surface of leaf blades glabrous or with simple trichomes Group 2
3 Abaxial surface of leaf blades with only branched trichomes > 4
4 Fruit valves glabrous Group 3
4 Fruit valves pubescent or puberulent (at least on margin) > 5
5 Abaxial surface of leaf blades with at least some 7-15-rayed trichomes Group 4
5 Abaxial surface of leaf blades with 2-4(-6)-rayed trichomes Group 5
6 Rachises glabrous > 7
6 Rachises sparsely to densely pubescent > 8
7 Abaxial surface of leaf blades glabrous (sometimes trichomes only on margins and apices) Group 6
7 Abaxial surface of leaf blades pubescent Group 7
8 Leaf blade margins not ciliate Group 8
8 Leaf blade margins ciliate > 9
9 Abaxial surface of leaf blades usually with simple or simple and branched trichomes, rarely glabrous Group 9
9 Abaxial surface of leaf blades with branched trichomes Group 10

Group 1

1 Cauline leaves 0 > 2
1 Cauline leaves 1-54(-76) > 7
2 Petals deeply 2-fid; rachises of fruiting racemes flexuous. Draba verna
2 Petals usually obtuse, rarely emarginate; rachises of fruiting racemes usually straight, if flexuous then petals yellow > 3
3 Petals white; late-season flowers apetalous; fruit valves usually with antrorse, simple trichomes, rarely glabrous > 4
3 Petals yellow; late-season flowers with petals; fruit valves usually glabrous, rarely puberulent > 5
4 Racemes 10-50(-70)-flowered, elongated in fruit, rachises densely pubescent; fruiting pedicels densely pubescent. Draba cuneifolia
4 Racemes (3-)5-12(-16)-flowered, subumbellate in fruit, rachises usually glabrous, rarely sparsely pubescent; fruiting pedicels glabrous or sparsely pubescent. Draba reptans
5 Abaxial surface of leaf blades glabrous or sparsely pubescent, trichomes simple and 2-rayed; stems usually glabrous, rarely pubescent proximally, trichomes simple. Draba crassifolia
5 Abaxial surface of leaf blades pubescent, trichomes 2-4-rayed; stems pubescent, trichomes 2-4-rayed (sometimes simple) > 6
6 Stems proximally with simple and 2-rayed trichomes; adaxial surface of leaf blades with simple and 2-rayed trichomes; anthers 0.15-0.25 mm; fruits (4-)6-12(-15) mm. Draba albertina
6 Stems proximally with 2-4-rayed trichomes; adaxial surface of leaf blades with 2-4-rayed trichomes; anthers 0.25-0.4 mm; fruits (8-)10-17(-20) mm. Draba stenoloba
7 Styles (0.8-)1-3.5 mm > 8
7 Styles 0.01-0.6 (-0.8) mm > 12
8 Adaxial surface of basal leaf blade pubescent with simple, subsetiform trichomes, rarely mixed with 2-rayed ones; fruit valves sparsely puberulent, trichomes simple. Draba bifurcata
8 Adaxial surface of basal leaf blade pubescent with at least some 2-4-rayed trichomes; fruit valves usually pubescent, rarely glabrous, trichomes 2-4-rayed > 9
9 Petals linear, 0.2-0.5 mm wide; s California. Draba corrugata
9 Petals oblanceolate to spatulate, 1-3.5 mm wide; se Arizona, Colorado, New Mexico, Utah > 10
10 Fruits plane, valves pubescent, trichomes 2-4-rayed; petals 3-5 × 1-1.5 mm, often fading whitish; Utah. Draba santaquinensis
10 Fruits slightly to strongly twisted, valves glabrous, pubescent, or puberulent, trichomes simple and 2(-4)-rayed; petals 5-8.5 × 1.5-3.5 mm, not fading whitish; Arizona, Colorado, New Mexico > 11
11 Cauline leaves (8-)12-31(-43); rachises pubescent; fruiting pedicels 4-10(-13) mm. Draba helleriana
11 Cauline leaves 1-3; rachises often glabrous or, rarely, sparsely pubescent; fruiting pedicels (6-)9-18(-22) mm. Draba mogollonica
12 Racemes bracteate basally; fruiting pedicels erect to ascending (subappressed to rachises); cauline leaves (15-)22-54(-76), densely overlapping proximally. Draba incana
12 Racemes ebracteate; fruiting pedicels horizontal to divaricate-ascending (not appressed to rachises); cauline leaves 1-15(-25), seldom overlapping > 13
13 Rachises glabrous > 14
13 Rachises pubescent > 18
14 Petals white or, rarely, absent; basal leaves not rosulate; racemes subumbellate in fruit. Draba reptans
14 Petals yellow; basal leaves rosulate; racemes elongated in fruit > 15
15 Cauline leaves 4-12(-15); fruiting pedicels 7-28(-35) mm, (1.5-)2-7 times longer than fruit. Draba nemorosa
15 Cauline leaves 1-3(-5); fruiting pedicels (1-)3-14(-19) mm, subequaling or shorter than fruit > 16
16 Abaxial surface of leaf blades glabrous or sparsely pubescent, trichomes simple and 2-rayed; stems usually glabrous, or, rarely, sparsely pubescent proximally, trichomes simple. Draba crassifolia
16 Abaxial surface of leaf blades pubescent, trichomes 2-4-rayed; stems pubescent basally, trichomes 2-4-rayed (sometimes simple) > 17
17 Stems proximally with simple and 2-rayed trichomes; adaxial surface of leaf blades with simple and 2-rayed trichomes; anthers 0.15-0.25 mm; fruits (4-)6-12(-15) mm. Draba albertina
17 Stems proximally with 2-4-rayed trichomes; adaxial surface of leaf blades with 2-4-rayed trichomes; anthers 0.25-0.4 mm; fruits (8-)10-17(-20) mm. Draba stenoloba
18 Leaf blade surfaces with cruciform trichomes > 19
18 Leaf blade surfaces with simple and 2-7-rayed trichomes > 20
19 Fruit valves pubescent; ovules 4-6(-8) per ovary. Draba aprica
19 Fruit valves glabrous; ovules 8-16(-20) per ovary. Draba brachycarpa
20 Fruits obovate to obovate-oblong. Draba platycarpa
20 Fruits elliptic, oblong, linear, lanceolate, or, rarely, ovate > 21
21 Late-season flowers apetalous; basal leaves not rosulate > 22
21 Late-season flowers with petals; basal leaves rosulate > 23
22 Racemes 10-50(-70)-flowered, elongated in fruit, rachises denselypubescent; fruiting pedicels densely pubescent. Draba cuneifolia
22 Racemes (3-)5-12(-16)-flowered, subumbellate in fruit, rachises glabrous or, rarely, sparsely pubescent; fruiting pedicels glabrous or sparsely pubescent. Draba reptans
23 Abaxial surface of leaf blades pubescent, trichomes 3-6-rayed; petals white. Draba praealta
23 Abaxial surface of leaf blades pubescent, trichomes 2-4-rayed; petals yellow (sometimes fading white) > 24
24 Styles 0.2-0.6(-0.8) mm; fruits 2-3.5 mm wide, valves pubescent, trichomes simple and 2-rayed. Draba brachystylis
24 Styles 0.01-0.15 mm; fruits 1.3-2.3 mm wide, valves glabrous or pubescent, trichomes simple > 25
25 Cauline leaves 3-10(-17); racemes (15-)20-51(-62)-flowered; fruits lanceolate, 6-9(-11) mm; Arizona, Colorado, New Mexico, Utah. Draba rectifructa
25 Cauline leaves 1 or 2(-4); racemes (2-)4-10(-15)-flowered; fruits usually linear, rarely linear-elliptic, (8-)10-17(-20) mm; Alaska, Alberta, British Columbia, Washington, Yukon. Draba stenoloba

Group 2

1 Plants stoloniferous; basal leaves not rosulate (subopposite). Draba ogilviensis
1 Plants not stoloniferous (usually cespitose); basal leaves rosulate > 2
2 Abaxial surface of leaf blades glabrous > 3
2 Abaxial surface of leaf blades pubescent > 9
3 Fruit valves pubescent, trichomes simple and 2-4-rayed; styles (0.7-)1.6-3 mm; petals 5.5-8 mm; n California and s Oregon. Draba howellii
3 Fruit valves glabrous or puberulent, trichomes simple; styles 0.02-1.2(-1.8) mm; petals 1.5-5(-6) mm; not California nor Oregon > 4
4 Racemes bracteate; basal leaf blades linear to linear-oblanceolate. Draba graminea
4 Racemes ebracteate; basal leaf blades usually obovate to oblanceolate, rarely linear-lanceolate > 5
5 Cauline leaves 1; fruits plane; styles 0.02-0.4(-0.6) mm > 6
5 Cauline leaves (1 or) 2-8; fruits slightly twisted or plane; styles (0.4-) 0.7-1.2(-1.8) mm > 7
6 Petals yellow (often fading white), oblanceolate, 1.5-2.5(-3) × 0.5-1 mm; stems glabrous or with simple trichomes; styles 0.02-0.1 mm. Draba crassifolia
6 Petals white, obovate, 3-5 × 1.8-3 mm; stems glabrous or with 2-8-rayed trichomes; styles 0.1-0.4(-0.6) mm. Draba lactea
7 Basal leaves undifferentiated into blade and petiole, 0.5-0.8 cm, persisting as a whole, imbricate, blade margins with setiform trichomes. Draba heilii
7 Basal leaves differentiated into blade and petiole, 1.2-8.5 cm, petiole persisting, not imbricate, blade margins without setiform trichomes > 8
8 Fruits lanceolate to ovate-lanceolate, (7-)8-14 × 3-5 mm; rachises pubescent (trichomes crisped); Colorado, Montana, Utah Wyoming. Draba crassa
8 Fruits linear-elliptic to elliptic, 5-10(-13) × 1.5-2.5 mm; rachises usually glabrous, rarely pubescent (trichomes non-crisped); se Arizona, s New Mexico, w Texas. Draba standleyi
9 Fruit valves pubescent, trichomes 2-12-rayed > 10
9 Fruit valves glabrous, pubescent, or puberulent, trichomes simple > 13
10 Styles 1.4-3.4 mm; cauline leaves (4-)6-10(-13); racemes (10-)18-55(-67)- flowered; petals yellow, linear. Draba corrugata
10 Styles 0.1-0.8 mm; cauline leaves 1-3; racemes 2-20-flowered; petals white, spatulate to obovate > 11
11 Fruits 2-5 × 1.5-2 mm; ovules 36-52 per ovary; petals 1.5-2 × 0.7-0.8 mm. Draba yukonensis
11 Fruits 4-9.5 × 2-4 mm; ovules 20-36 per ovary; petals 3-5 × 1.5-2.5 mm > 12
12 Fruits with 2-4-rayed and, sometimes, fewer, simple trichomes; petals 3-4 mm; stems proximally with branched trichomes 2-6-rayed. Draba arctogena
12 Fruits with (2-)5-12-rayed trichomes; petals 3.5-5 mm; stems proximally with branched trichomes 4-10-rayed. Draba oblongata
13 Styles (0.7-)1-3 mm; fruits usually twisted, rarely plane; petals (4-)4.5-7.5 mm > 14
13 Styles 0.01-1(-1.2) mm; fruits not or, rarely, slightly twisted; petals 1.5-4(-4.5) mm > 17
14 Cauline leaf blade margins dentate; fruiting pedicels horizontal to divaricate; se Arizona. Draba bifurcata
14 Cauline leaf blade margins entire; fruiting pedicels usually ascending, rarely divaricate-ascending; Arizona, Colorado, New Mexico, Texas, Wyoming > 15
15 Fruits usually twisted (to 3 turns), rarely plane; stems proximally with trichomes 0.4-2.2 mm; ovules 20-34 per ovary; c Colorado, n New Mexico, se Wyoming. Draba streptocarpa
15 Fruits usually twisted (to 1 turn), rarely plane; stems proximally with trichomes 0.1-0.7 mm; ovules 12-24 per ovary; se Arizona, s New Mexico, w Texas > 16
16 Basal leaves undifferentiated into blade and petiole, 0.5-0.8 cm, persisting as a whole, imbricate, blade margins with setiform trichomes. Draba heilii
16 Basal leaves differentiated into blade and petiole, 1.2-8.5 cm, petiole persisting, not imbricate, blade margins without setiform trichomes. Draba standleyi
17 Annuals, biennials, or perennials (not cespitose); fruiting pedicels (3-)5-14 (-16) mm > 18
17 Perennials (cespitose); fruiting pedicels 1-6 mm > 19
18 Abaxial surface of leaf blades pubescent with 2-4-rayed trichomes; stems pubescent, trichomes simple and 2-rayed. Draba albertina
18 Abaxial surface of leaf blades glabrous or with some simple and 2-rayed trichomes; stems usually glabrous, rarely pubescent basally, trichomes simple. Draba crassifolia
19 Petals yellow, 1-2 mm wide; styles (0.2-)0.3-1.2 mm > 20
19 Petals white, 0.4-1(-1.5) mm wide; styles 0.05-0.2(-0.3) mm > 22
20 Abaxial surface of leaf blades with sessile or subsessile, appressed, 2-4-rayed trichomes; fruits ovate, 4-8 mm; styles 0.2-0.3 mm. Draba weberi
20 Abaxial surface of leaf blades with stalked 2- or 3-rayed trichomes; fruits lanceolate to oblong-lanceolate, 4-13 mm; styles 0.3-1.2 mm > 21
21 Petals 2-2.5(-3) mm, erect, not clawed; anthers oblong, 0.6-0.9 mm; fruits plane; rachises usually glabrous, rarely sparsely pubescent. Draba exunguiculata
21 Petals 3-4.5 mm, not erect (flared, clawed); anthers ovate, 0.3-0.5 mm; fruits twisted or plane; rachises pubescent. Draba grayana
22 Fruit valves glabrous; stems glabrous or, rarely, sparsely pubescent (trichomes straight); petals 2-3.5 × 0.8-1.5 mm. Draba fladnizensis
22 Fruit valves usually pubescent, rarely glabrous; stems pubescent (trichomes crisped); petals 1.5-2 × 0.4-0.8 mm > 23
23 Racemes 2-7-flowered, rachises glabrous; sepals caducous; fruits lanceolate, flattened; Yukon. Draba kluanei
23 Racemes (3-)6-13(-17)-flowered, rachises pubescent or, rarely, glabrous; sepals persistent; fruits ovoid to subellipsoid, slightly inflated basally; e California. Draba monoensis

Group 3

1 Basal leaf blade surfaces with malpighiaceous trichomes. Draba malpighiacea
1 Basal leaf blade surfaces with simple, 2-rayed, forked, stellate, or dendritic trichomes > 2
2 Abaxial surface of leaf blades with some 7-15-rayed trichomes > 3
2 Abaxial surface of leaf blades with 2-5 (or 6)-rayed trichomes > 11
3 Petals yellow; stem and basal leaf trichomes crisped. Draba streptobrachia
3 Petals white or creamy white; stem and basal leaf trichomes usually non-crisped > 4
4 Margins of basal and cauline leaf blades entire > 5
4 Margins of basal and, sometimes, cauline leaf blades usually dentate or denticulate, if entire, racemes not flexuous in fruit > 8
5 Plants usually forming mats; rachises slightly flexuous > 6
5 Plants not forming mats; rachises not flexuous > 7
6 Fruits 6-15(-18) mm; adaxial surface of leaf blades with simple and long-stalked, 2-rayed trichomes. Draba lonchocarpa
6 Fruits 3.5-9 mm; adaxial surface of leaf blades with short-stalked, 8-15-rayed trichomes. Draba nivalis
7 Rachises pubescent; ovules 22-32 per ovary; sepals persistent (until fruiting); e California, w Nevada. Draba californica
7 Rachises glabrous; ovules 12-16 per ovary; sepals caducous; Alaska, Alberta, w Montana, nw Wyoming. Draba porsildii
8 Cauline leaves usually 0, rarely 1 (as a bract); basal leaf blades each with prominent midvein; sepals glabrous or, rarely, with simple trichomes subapically. Draba lactea
8 Cauline leaves usually 2-25, rarely 1 (D. chamissonis); basal leaf blades each with obscure midvein; sepals with 2-5-rayed trichomes > 9
9 Fruits 1.1-1.6(-2) mm wide; petals 2-3.5 mm; petiole margins not ciliate; proximalmost flowers bracteate. Draba chamissonis
9 Fruits 2-3.5 mm wide; petals 3.5-5.5 mm; petiole margins ciliate; proximalmost flowers usually ebracteate (sometimes bracteate in D. glabella) > 10
10 Abaxial surface of leaf blades with sessile, stellate trichomes; styles (0.2-)0.4-1 mm; stems proximally with 8-12-rayed trichomes. Draba arabisans
10 Abaxial surface of leaf blades with short-stalked, stellate trichomes; styles 0.05-0.2(-0.5) mm; stems proximally with some simple trichomes. Draba glabella
11 Stem and leaf trichomes sessile, 2 rays parallel to long axis of stem or midvein, some malpighiaceous. Draba spectabilis
11 Stem and leaf trichomes stalked, rays not parallel to long axis of stem or midvein, not malpighiaceous > 12
12 Caudex fleshy, simple; petiole of basal leaves (1-)4-15 cm; fruits 4-7(-9) mm wide. Draba grandis
12 Caudex not fleshy, usually branched, rarely simple; petiole of basal leaves obsolete or 1-2 cm; fruits 1-4(-6) mm wide > 13
13 Abaxial surface of leaf blades with either cruciform or pectinate trichomes > 14
13 Abaxial surface of leaf blades with cruciform and 2-6-rayed trichomes > 15
14 Plants pulvinate, caudex densely branched; abaxial surface of leaf blades with pectinate trichomes; ovules 8-16(-20) per ovary. Draba incerta
14 Plants not pulvinate, caudex loosely branched; abaxial surface of leaf blades with cruciform trichomes; ovules 16-30 per ovary. Draba juvenilis
15 Seeds 1.8-2.8 × 1.2-2 mm, wing 0.5-1 mm wide; fruits (3.5-)4-6 mm wide. Draba asterophora
15 Seeds 0.7-1.4(-1.6) × 0.4-0.8(-1) mm, not winged; fruits 1-4(-5) mm wide > 16
16 Styles (0.6-)0.8-3.6 mm; petals 4-8.5 mm; anthers usually oblong (ovate in D. murrayi) > 17
16 Styles 0.01-0.6 mm; petals 1.8-4 mm; anthers ovate > 19
17 Petals white; anthers ovate, 0.4-0.5 mm; fruits 1.5-2 mm wide; styles 0.6-1.5 mm. Draba murrayi
17 Petals yellow; anthers oblong, 0.6-1 mm; fruits 2-5 mm wide; styles (0.8-)1-3.6 mm > 18
18 Fruits plane; ovules 10-18 per ovary; basal leaf blades (2-) 4-10(-14) mm wide; cauline leaves (3-)5-9(-11); petals 4-6 mm. Draba abajoensis
18 Fruits slightly twisted; ovules 24-36 per ovary; basal leaf blades 7-25(-33) mm wide; cauline leaves 1-3; petals (5-) 6-8.5 mm. Draba mogollonica
19 Rachises usually glabrous, (rarely sparsely pubescent in D. stenoloba); fruits usually linear, elliptic, or linear-lanceolate, rarely lanceolate, 1-2(-2.5) mm wide; styles 0.01-0.15(-0.2) mm > 20
19 Rachises pubescent; fruits lanceolate to oblong or ovoid, (1.8-) 2-4 mm wide; styles 0.1-0.6 mm > 22
20 Sepals pubescent, trichomes simple and 2- or 3-rayed; abaxial surface of leaf blades with trichomes (2-)4(-6)-rayed. Draba paucifructa
20 Sepals glabrous or sparsely pubescent, trichomes simple; abaxial surface of leaf blades with trichomes 2-4-rayed > 21
21 Stems proximally with simple and 2-rayed trichomes; adaxial surface of leaf blades with simple and 2-rayed trichomes; anthers 0.15-0.25 mm; fruits (4-)6-12 (-15) mm. Draba albertina
21 Stems proximally with 2-4-rayed trichomes; adaxial surface of leaf blades with 2-4-rayed trichomes; anthers 0.25-0.4 mm; fruits (8-)10-17(-20) mm. Draba stenoloba
22 Petals yellow; fruits ovoid to ovoid-lanceolate, inflated (at least basally); ovules (4-)8-12 per ovary. Draba sobolifera
22 Petals white or creamy white; fruits oblong, lanceolate, or lanceolate-elliptic, flattened; ovules 18-32 per ovary > 23
23 Fruiting pedicels pubescent, trichomes 4-8-rayed; sepals persistent; petals 0.8-1 mm wide; e California, w Nevada. Draba californica
23 Fruiting pedicels pubescent, trichomes simple and 2-4-rayed; sepals caducous; petals 1.7-2.5 mm wide; Canada, Greenland. Draba norvegica

Group 4

1 Fruit trichomes 2-7-rayed (at least on replum); petals white > 2
1 Fruit trichomes simple and 2-5-rayed; petals white or yellow > 8
2 Racemes bracteate (at least basally) > 3
2 Racemes ebracteate > 4
3 Racemes (10-)15-47(-63)-flowered, often considerably elongated in fruit; ovules 28-48 per ovary. Draba cana
3 Racemes 2-5(-8)-flowered, slightly elongated in fruit; ovules 16-24 per ovary. Draba inexpectata
4 Petals 2-3.5 × 0.7-1.4 mm; fruits 1.5-2.5 mm wide > 5
4 Petals 3.5-6 × 1.5-2.5 mm; fruits 2-3.5 mm wide > 6
5 Cauline leaves 1-3(-6); fruits usually twisted, rarely plane; rachises not flexuous in fruit; ovules 28-40 per ovary; California. Draba breweri
5 Cauline leaf 1; fruits plane; rachises often slightly flexuous in fruit; ovules 12-24(-28) per ovary; Alaska, Canada, Greenland. Draba nivalis
6 Basal leaf blade margins dentate or denticulate; fruits usually slightly twisted, rarely plane; styles (0.2-)0.4-1 mm. Draba arabisans
6 Basal leaf blade margins usually entire, rarely 1-toothed on each side; fruits plane; styles 0.1-0.6 mm > 7
7 Basal leaf blades with simple trichomes apically, abaxial surfaces with distinct midveins; seeds 0.8-1.1 × (0.6-)0.7-0.8 mm. Draba arctica
7 Basal leaf blades without simple trichomes apically, abaxial surfaces with obscure midveins; seeds 0.6-0.8 × 0.4-0.6 mm. Draba cinerea
8 Petals yellow > 9
8 Petals white > 11
9 Ovules 28-38(-44) per ovary; racemes basally bracteate, (10-)18-52(-72)-flowered; cauline leaves 5-20(-26); fruits (6-)9-14(-17) mm, often subappressed to rachis; stem trichomes non-crisped. Draba aurea
9 Ovules 6-16(-18) per ovary; racemes ebracteate, 3-15(-18)-flowered; cauline leaves 1-4 (or 5); fruits 3-10 mm, not appressed to rachis; stem trichomes often crisped > 10
10 Plants matted, caudex branches creeping; stem trichomes dendritic; ovules 6-12 per ovary; se Utah. Draba ramulosa
10 Plants not matted, caudex branches not creeping; stem trichomes stellate; ovules 10-16(-18) per ovary; Colorado. Draba streptobrachia
11 Styles (0.7-)1-2(-2.3) mm; fruits twisted; sw Colorado. Draba smithii
11 Styles 0.05-0.6(-0.8) mm; fruits plane or slightly twisted; not sw Colorado > 12
12 Leaf blade margins dentate or denticulate; cauline leaves 2-25 > 13
12 Leaf blade margins entire; cauline leaves 1(-4) > 14
13 Leaf blade surfaces pubescent, trichomes cruciform or (2-)4-6-rayed (rays usually simple, rarely branched); plants with rhizomatous caudex. Draba borealis
13 Leaf blade surfaces pubescent, trichomes stellate-pectinate, 4-8(-12)- rayed; plants without rhizomatous caudex (sometimes cespitose). Draba glabella
14 Rachises not flexuous; sepals persistent; fruits plane. Draba californica
14 Rachises often slightly flexuous; sepals caducous; fruits slightly twisted or plane. Draba lonchocarpa

Group 5

1 Fruit trichomes 2-rayed and/or simple > 2
1 Fruit trichomes 4-rayed (some) (except D. saxosa 2- or 3-rayed) > 12
2 Stem and leaf trichomes sessile, 2 rays parallel to long axis of stem or midvein, some trichomes malpighiaceous. Draba spectabilis
2 Stem and leaf trichomes stalked, rays not parallel to long axis of stem or midvein, not malpighiaceous > 3
3 Abaxial surface of basal leaf blades with cruciform trichomes > 4
3 Abaxial surface of basal leaf blades with 2-6-rayed trichomes > 5
4 Fruits plane; styles 0.2-0.7 mm; Alaska, Canada. Draba juvenilis
4 Fruits often strongly twisted; styles 0.8-1.8(-2.5) mm; Arizona. Draba petrophila
5 Fruits appressed or subappressed to rachises; proximalmost flowers bracteate. Draba aurea
5 Fruits not appressed to rachises; proximalmost flowers ebracteate > 6
6 Styles (1-)1.5-3.5 mm. Draba helleriana
6 Styles usually 0.01-0.9 mm, if longer (D. pennellii), plants pulvinate or petals white > 7
7 Plants not cespitose or pulvinate, caudex simple or poorly developed; fruits (7-)10-17(-20) mm; ovules 20-36(-42) per ovary > 8
7 Plants cespitose or pulvinate, caudex branched; fruits (3-)4-9 (-14) mm; ovules (4-)8-24 per ovary > 9
8 Fruits narrowly elliptic to lanceolate, 2-3.5 mm wide; styles 0.2-0.6(-0.8) mm; racemes (5-)10-35(-47)-flowered; ne Nevada, Utah. Draba brachystylis
8 Fruits linear to linear-elliptic, 1.5-2 mm wide; styles 0.01-0.15 mm; racemes (2-)4-10(-15)-flowered; Alaska, Alberta, British Columbia, Washington, Yukon. Draba stenoloba
9 Seeds 1.8-2.8 × 1.2-2 mm, winged. Draba asterophora
9 Seeds 0.7-1.8 × 0.4-1 mm, not winged > 10
10 Petals white; cauline leaves 1-4; styles (0.7-)1-1.8(-2.1) mm; fruits slightly twisted or plane; e Nevada. Draba pennellii
10 Petals yellow (or fading white); cauline leaves 1; styles 0.2-0.9 mm; fruits plane; Nevada and elsewhere > 11
11 Fruits flattened; abaxial surface of leaf blades with pectinate and sometime 4-6-rayed trichomes; petals yellow (fading white), 4-6 mm. Draba incerta
11 Fruits inflated (at least basally); abaxial surface of leaf blades with 2-4-rayed trichomes; petals yellow, 3-4 mm. Draba sobolifera
12 Caudices simple, plants not cespitose > 13
12 Caudices branched, plants cespitose (branches sometimes surculose or rhizomatous) > 18
13 Petals white; styles 0.03-0.1(-0.15) mm. Draba praealta
13 Petals yellow, rarely fading whitish; styles (0.5-)0.9-3.5 mm > 14
14 Cauline leaves 1-5; sepals with 2-4-rayed trichomes > 15
14 Cauline leaves 5-33(-43); sepals glabrous or with some simple trichomes > 16
15 Petals (5-)6-8.5 × 2.2-3.5 mm; fruits slightly twisted; ovules 24-36 per ovary; styles (0.8-)1-2.2 mm; se Arizona, w New Mexico. Draba mogollonica
15 Petals 3-5 × 1-1.5 mm; fruits plane; ovules 14-22 per ovary; styles 0.9-1.2 mm; nc Utah. Draba santaquinensis
16 Fruits 3-5 mm wide, plane; stems 0.3-1.5 dm; petals 0.5-1(-1.2) mm wide. Draba aureola
16 Fruits 2-3.5 mm wide, usually twisted, rarely plane; stems (0.5-)1-4.3 (-5.2) dm; petals 1.5-2.5 mm wide > 17
17 Styles 0.5-1.2(-1.5) mm; petals 3.5-5 mm; ovules 28-38(-44) per ovary; fruits often subappressed to rachises. Draba aurea
17 Styles (1-)1.5-3.5 mm; petals 5-7 mm; ovules 14-28 per ovary; fruits not appressed to rachises. Draba helleriana
18 Basal and often cauline leaf blade margins dentate; petals white > 19
18 Basal and cauline leaf blade margins usually entire, sometimes denticulate (D. viridis); petals yellow (unknown in D. trichocarpa) > 21
19 Styles (1-)1.5-3(-4) mm (sparsely pubescent); ovules 4-10(-12) per ovary; fruits often strongly twisted. Draba ramosissima
19 Styles (0.01-)0.1-0.6(-0.8) mm (glabrous); ovules 16-28(-30) per ovary; fruits plane or slightly twisted > 20
20 Petals 4-6 mm; fruits (5-)7-12 × 2.5-4.5 mm, slightly twisted or plane; Alaska, w Canada. Draba borealis
20 Petals 2.5-4 mm; fruits 4-8 × 2-3 mm, plane; e Canada, Greenland. Draba norvegica
21 Styles 0.3-1.2(-1.4) mm; ovules 8-12 per ovary; Idaho, Nevada > 22
21 Styles (0.7-)1.2-3.5 mm; ovules 8-24 per ovary; s Arizona, California, s Oregon > 23
22 Basal leaf blades 6-19(-24) × 2-5(-8) mm; styles 0.5-1.2(-1.4) mm; petals 3.5-5 mm; fruiting pedicels (3-)4-8 mm; Nevada. Draba arida
22 Basal leaf blades 2-4 × 0.5-1.5 mm; styles 0.3-0.7 mm; petals 2-4 mm; fruiting pedicels 1-4.5 mm; Idaho. Draba trichocarpa
23 Cauline leaves 5-16; fruits 3.5-8 mm; leaf blade surfaces with cruciform trichomes; s Arizona. Draba viridis
23 Cauline leaves 1-3 (or 4); fruits 6-11(-15) mm; leaf blade surfaces with 2- or 3-rayed trichomes; California, Oregon > 24
24 Petals 5.5-8 mm; cauline leaves 1-3 (or 4); fruits lanceolate to broadly ovate, plane; n California, s Oregon. Draba howellii
24 Petals 3-3.5 mm; cauline leaves 1; fruits oblong to linear-oblong, slightly twisted or plane; s California. Draba saxosa

Group 6

1 Branched trichomes sessile, malpighiaceous; Greenland. Draba sibirica
1 Branched trichomes stalked, not malpighiaceous, sometimes only simple cilia present; not Greenland (except D. crassifolia and D. lactea) > 2
2 Fruits 10-23 mm; seeds orbicular, 3-4.5 mm, broadly winged. Draba carnosula
2 Fruits 2.5-11(-16) mm; seeds ovoid, oblong, or elliptic, 0.7-2(-2.6) mm, not winged > 3
3 Plants stoloniferous; basal leaves not rosulate. Draba ogilviensis
3 Plants not stoloniferous (usually cespitose or pulvinate); basal leaves rosulate > 4
4 Petals white > 5
4 Petals yellow (rarely fading white) > 10
5 Petals 5-6.5 mm; styles 0.6-1.8(-2.5) mm; Nevada. Draba serpentina
5 Petals 2.5-4.5(-5) mm; styles 0.1-0.9(-1.2) mm; not Nevada > 6
6 Fruits inflated (at least basally); racemes (6-)10-28(-40)-flowered. Draba subalpina
6 Fruits flattened; racemes 2-8(-12)-flowered > 7
7 Ovules (10-)14-22(-26) per ovary; petals 1.8-3 mm wide; Alaska, Canada, Greenland > 8
7 Ovules 8-16 per ovary; petals 1.2-2 mm wide; Idaho, Montana, Utah, Wyoming > 9
8 Petiole and midvein of basal leaves thickened; basal leaves (1-)2-6 mm wide; styles 0.1-0.4 mm. Draba lactea
8 Petiole and midvein of basal leaves not thickened; basal leaves 1-2 mm wide; styles 0.4-1 mm. Draba mulliganii
9 Basal leaf blade apex acute; fruits ovate, plane, 2.5-4 mm wide; fruiting pedicels 2-6 mm; sepals persistent. Draba globosa
9 Basal leaf blade apex obtuse; fruits ± oblong, slightly twisted, 1.5-3 mm wide; fruiting pedicels 4-13 mm; sepals caducous. Draba oreibata
10 Fruits inflated (at least basally) > 11
10 Fruits flattened > 12
11 Adaxial surface of leaf blades with simple and 2-rayed trichomes; styles 0.1-0.5 mm. Draba macounii
11 Adaxial surface of leaf blades with 2-4-rayed trichomes; styles 0.3-1(-1.3) mm. Draba sphaeroides
12 Styles (0.5-)0.7-3 mm; petals (4-)5-8 mm; sepals 2-4 mm > 13
12 Styles 0.02-0.8(-1) mm; petals 1.5-4(-6) mm; sepals 1-3 mm > 15
13 Leaf blade margins ciliate with subsetiform, simple trichomes. Draba burkei
13 Leaf blade margins not ciliate, often with some branched trichomes > 14
14 Fruits 6-11(-15) × 3-5 mm; styles (0.7-)1.6-3 mm; ovules 8-22 per ovary; California, Oregon. Draba howellii
14 Fruits (3-)4-6.5(-8) × 2-3.2 mm; styles 0.6-1.7 mm; ovules 4-8 per ovary; Utah. Draba maguirei
15 Plants without sterile rosettes or shoots, not pulvinate or matted, caudex simple or branched; petals 0.5-1 mm wide; ovules (8-)16-24(-30) per ovary; seeds 0.7-0.8 mm. Draba crassifolia
15 Plants often with sterile rosettes or shoots, pulvinate or loosely matted, caudex branched; petals 1-3 mm wide; ovules 4-16 per ovary; seeds 1-2(-2.6) mm > 16
16 Fruiting pedicels decurrent basally. Draba incrassata
16 Fruiting pedicels not decurrent basally > 17
17 Plants loosely matted; racemes considerably elongated in fruit. Draba cruciata
17 Plants pulvinate; racemes not or slightly elongated in fruit > 18
18 Leaf blades with prominent midvein abaxially; fruit valves pubescent or puberulent. Draba densifolia
18 Leaf blades with obscure midvein; fruit valves glabrous > 19
19 Leaves fleshy, blade apex obtuse; fruiting pedicels 4-10 mm; fruit valves obscurely veined. Draba daviesiae
19 Leaves not fleshy, blade apex acute; fruiting pedicels 2-6 mm; fruit valves distinctly veined. Draba globosa

Group 7

1 Abaxial surface of leaf blades with some 7-16-rayed trichomes > 2
1 Abaxial surface of leaf blades with simple and/or 2-5 (or 6)-rayed or malpighiaceous trichomes > 9
2 Trichomes pectinate; leaf blades with midvein prominent abaxially; fruits inflated (at least basally). Draba oligosperma
2 Trichomes stellate or, rarely, subdendritic; leaf blades with midvein obscure abaxially (prominent in D. lactea); fruits flattened > 3
3 Leaf blades with midvein strongly thickened abaxially. Draba lactea
3 Leaf blades with midvein obscure abaxially > 4
4 Petals white, 2-4 mm > 5
4 Petals yellow (white fading yellowish in D. palanderiana), 4-6 mm > 7
5 Fruits linear to narrowly lanceolate or oblong, 6-15(-18) mm; ovules 16-24(-28) per ovary; rachises often slightly flexuous. Draba lonchocarpa
5 Fruits ovate to oblong, 4-8 mm; ovules 12-16 per ovary; rachises not flexuous > 6
6 Fruits not appressed to rachises; petals 2-3 mm wide; fruiting pedicels (4-)5-9 mm; style 0.4-1 mm. Draba mulliganii
6 Fruits appressed to rachises; petals 0.7-1.2 mm wide; fruiting pedicels 0.5-2(-4) mm; style 0.05-0.1 mm. Draba porsildii
7 Ovules 18-32 per ovary; seeds 0.9-1.1 × 0.5-0.7 mm; fruit valves glabrous. Draba palanderiana
7 Ovules 8-16 per ovary; seeds 1.2-2 × 0.8-1.3 mm; fruit valves often puberulent, sometimes glabrous > 8
8 Styles (0.7-)1-1.8(-2.4) mm; petiole bases and leaf blade margins not ciliate; sepals pubescent, trichomes 4-6-rayed; Idaho. Draba argyrea
8 Styles 0.5-0.9(-1.1) mm; petiole bases and leaf blade margins ciliate; sepals pubescent, trichomes simple and 2-rayed; Alaska, British Columbia, Washington, Yukon. Draba ruaxes
9 Leaf blades with malpighiaceous trichomes. Draba sibirica
9 Leaf blades with simple, forked, stellate, or subdendritic trichomes > 10
10 Abaxial surface of leaf blades with mixture of simple and 2(-4)-rayed trichomes > 11
10 Abaxial surface of leaf blades with 2-6-rayed trichomes > 18
11 Petals yellow (rarely fading white); fruits not inflated basally (flattened) > 12
11 Petals white; fruits inflated basally (flattened in D. fladnizensis) > 15
12 Perennials with poorly developed caudex, not stoloniferous; petals 1.5-3.2 × 0.5-1.2 mm; styles 0.01-0.12 mm; ovules (20-)24-38(-44) per ovary > 13
12 Perennials with branched caudex or stoloniferous; petals 3.5-6 × 2-3.5 mm; styles 0.4-1 mm; ovules 8-20 per ovary > 14
13 Abaxial surface of leaf blades pubescent with 2-4-rayed trichomes; stems pubescent, trichomes simple and 2-4-rayed. Draba albertina
13 Abaxial surface of leaf blades glabrous or with some simple and 2-rayed trichomes; stems usually glabrous, rarely sparsely pubescent basally, trichomes simple. Draba crassifolia
14 Plants stoloniferous; basal leaves not rosulate, blades with obscure midvein; fruits oblong, 2-3 mm wide. Draba ogilviensis
14 Plants not stoloniferous; basal leaves rosulate, blades with prominent, persistent midvein; fruits elliptic to lanceolate, 3-4 mm wide. Draba pilosa
15 Basal leaf blades with a prominent midvein > 16
15 Basal leaf blades with obscure midvein > 17
16 Fruits flattened, elliptic-lanceolate to oblong, 1.5-2 mm wide; rachises glabrous; petals 2-3.5 mm. Draba fladnizensis
16 Fruits slightly inflated, ovoid to oblong, 2-3 mm wide; rachises usually pubescent, rarely glabrous; petals 1.5-2(-2.5) mm. Draba subcapitata
17 Sepals persistent; fruiting pedicels 1-2.5(-4) mm; petals 1.5-2 mm; fruits (2-)3-5 × (1.2-)1.5-2.5 mm; e California. Draba monoensis
17 Sepals caducous; fruiting pedicels (3-)5-10(-17) mm; petals 3-5 mm; fruits 4-8(-10) × 2.5-4 mm; s Utah. Draba subalpina
18 Caudex simple or branched, without sterile rosettes; styles 0.01-0.15(-0.2) mm > 19
18 Caudex often branched, with sterile rosettes; styles (0.1-)0.2-3 mm > 21
19 Sepals pubescent with simple and 2- or 3-rayed trichomes; abaxial surface of leaf blades with (2-)4(-6)-rayed trichomes; s Nevada. Draba paucifructa
19 Sepals glabrous or with simple trichomes; abaxial surface of leaf blades with 2-4-rayed trichomes; not s Nevada > 20
20 Stems proximally with simple and 2-rayed trichomes; adaxial surface of leaf blades with simple and 2-rayed trichomes; anthers 0.15-0.25 mm; fruits (4-)6-12(-15) mm. Draba albertina
20 Stems proximally with 2-4-rayed trichomes; adaxial surface of leaf blades with 2-4-rayed trichomes; anthers 0.25-0.4 mm; fruits (8-) 10-17(-20) mm. Draba stenoloba
21 Abaxial surface of leaf blades with some pectinate or submalpighiaceous trichomes > 22
21 Abaxial surface of leaf blades with cruciform or 2-5-rayed trichomes > 23
22 Abaxial surface of leaf blades with pectinate and some 4-6-rayed trichomes; ovules 8-16(-20) per ovary. Draba incerta
22 Abaxial surface of leaf blades with submalpighiaceous trichomes; ovules 20-28 per ovary. Draba kassii
23 Fruits inflated (at least basally) > 24
23 Fruits flattened > 26
24 Styles 0.1-0.5 mm; fruiting pedicels not expanded basally; anthers 0.2-0.3 mm; Alaska, Alberta, British Columbia, Montana, Yukon. Draba macounii
24 Styles 0.3-1(-1.3) mm; fruiting pedicels usually expanded basally; anthers 0.4-0.5 mm; Nevada, Utah > 25
25 Plants densely pulvinate; petals 2.7-4 mm; fruiting pedicels divaricate- ascending. Draba sphaeroides
25 Plants loosely cespitose; petals 3.5-5.5 mm; fruiting pedicels divaricate, horizontal, or slightly descending. Draba pedicellata
26 Seeds 1.8-2.8 × 1.2-2 mm, winged. Draba asterophora
26 Seeds 0.7-2(-2.6) × 0.4-1(-1.4) mm, not winged > 27
27 Fruits twisted, curved. Draba sharsmithii
27 Fruits plane, not curved (straight) > 28
28 Leaf blades with prominent midveins, margins ciliate (trichomes simple). Draba densifolia
28 Leaf blades with obscure midveins, margins not ciliate > 29
29 Fruits 2.5-4.5(-5.5) mm wide; rachises often flexuous; fruiting pedicels expanded basally or not. Draba pedicellata
29 Fruits 1.5-3 mm wide; rachises not flexuous; fruiting pedicels not expanded basally > 30
30 Ovules 4-10(-12) per ovary; seeds 0.8-1.3 mm wide > 31
30 Ovules 12-30 per ovary; seeds 0.4-0.8 mm wide > 32
31 Styles (0.1-)0.3-0.8 mm; petals 4-5(-6) × 1.2-2 mm; sepals 1.5-2 mm; ec California. Draba cruciata
31 Styles 0.6-1.7 mm; petals 5-7 × 2-3 mm; sepals 2.5-4 mm; n Utah. Draba maguirei
32 Abaxial surface of leaf blades pubescent, trichomes cruciform; racemes (2-)4-13(-18)-flowered; petals 3-5 mm; Alaska, Alberta, British Columbia, Northwest Territories, Yukon. Draba juvenilis
32 Abaxial surface of leaf blades pubescent, trichomes (2-)4 (or 5)-rayed; racemes 14-36-flowered; petals 5-6 mm; sw Utah. Draba zionensis

Group 8

1 Abaxial surface of leaf blades with pectinate, subpectinate, subdendritic, or stellate with 7-16-rayed trichomes > 2
1 Abaxial surface of leaf blades with simple, cruciform, or 2-4(-6)-rayed trichomes > 12
2 Leaves, pedicels, and sepals with sessile or subsessile, pectinate trichomes > 3
2 Leaves, pedicels, and sepals with stalked, stellate to subdendritic trichomes > 5
3 Fruit valves pubescent, trichomes pectinate; ovules 4-8 per ovary. Draba pectinipila
3 Fruit valves glabrous or pubescent, trichomes simple or 2-rayed; ovules (6-)8-16 (-20) per ovary > 4
4 Fruits 5-9(-11) mm, flattened; petals 4-6 mm; sepals 2.5-3.5(-4) mm; leaf midvein usually obscure. Draba incerta
4 Fruits 3-6(-7) mm, inflated; petals 2.5-4 mm; sepals 1.5-3 mm; leaf midvein prominent. Draba oligosperma
5 Petals white or creamy white > 6
5 Petals yellow > 9
6 Sepals caducous; fruit valves glabrous; Alaska, Northwest Territories, Yukon > 7
6 Sepals persistent; fruit valves usually pubescent, rarely glabrous (D. californica); e California, w Nevada > 8
7 Stems pubescent throughout, trichomes 8-15-rayed; petals spatulate to oblanceolate, 2-3.5 × 0.8-1.4 mm; rachises and fruiting pedicels pubescent; styles 0.1-0.4 mm. Draba nivalis
7 Stems pubescent proximally, trichomes 2-9-rayed; petals obovate, 4.4-5.5 × 2-3 mm; rachises and fruiting pedicels usually glabrous, rarely sparsely pubescent; styles 0.3-0.8 mm. Draba palanderiana
8 Fruits usually twisted, rarely plane, with 2-5-rayed trichomes; fruiting pedicels 1.5-3(-4) mm. Draba breweri
8 Fruits plane, with simple and 2- or 3-rayed trichomes, rarely glabrous; fruiting pedicels (2-)4-9(-12) mm. Draba californica
9 Fruits 4-11 mm, flattened, twisted or plane > 10
9 Fruits 2-5(-6) mm, inflated (at least basally), plane > 11
10 Styles (0.7-)1-1.8(-2.4) mm; fruits symmetric; fruiting pedicels (4-) 5-12(-19) mm; c Idaho. Draba argyrea
10 Styles (0.1-)0.3-0.7(-1) mm; fruits often asymmetric; fruiting pedicels 2-5(-7) mm; ec California. Draba sierrae
11 Racemes (4-)6-18(-23)-flowered, elongated in fruit; petals 4-6 mm; fruiting pedicels 4-9(-13) mm; c Idaho. Draba sphaerocarpa
11 Racemes 2-5(-10)-flowered (subumbellate), not or slightly elongated in fruit; petals 2.8-4 mm; fruiting pedicels 1.5-3(-6) mm; e California, w Nevada. Draba subumbellata
12 Plants stoloniferous; basal leaves not rosulate. Draba ogilviensis
12 Plants not stoloniferous (usually cespitose); basal leaves usually rosulate > 13
13 Petals white > 14
13 Petals yellow > 16
14 Sepals persistent; fruits slightly inflated basally; petals 1.5-2 × 0.5-0.6 mm. Draba monoensis
14 Sepals caducous; fruits flattened; petals 2-6 × 0.8-2.8 mm > 15
15 Styles 0.1-0.7 mm; fruit valves usually glabrous, rarely pubescent, trichomes simple (along margin); Alaska, Alberta, British Columbia, Northwest Territories, Yukon. Draba juvenilis
15 Styles (0.7-)1-1.8(-2.1) mm; fruit valves with simple and 2-rayed trichomes; e Nevada. Draba pennellii
16 Abaxial surface of leaf blades with cruciform trichomes; ovules 16-30 per ovary. Draba juvenilis
16 Abaxial surface of leaf blades with 2-6-rayed trichomes; ovules 4-18(-22) per ovary > 17
17 Racemes (15-)30-75-flowered; Arizona. Draba asprella
17 Racemes 3-20(-27)-flowered; not Arizona > 18
18 Styles (0.7-)1.6-3 mm; petals 5.5-8 mm; anthers 0.7-0.9 mm. Draba howellii
18 Styles 0.3-1.4 mm; petals 3.5-5.5(-6) mm; anthers 0.4-0.6 mm > 19
19 Fruit valves glabrous or pubescent, trichomes simple and 2-rayed; fruiting pedicels usually expanded basally > 20
19 Fruit valves pubescent, trichomes 2-6-rayed; fruiting pedicels not expanded basally > 21
20 Petals 3.5-5.5 mm; fruiting pedicels horizontal to divaricate; ovules 8-16 per ovary. Draba pedicellata
20 Petals 2.7-4 mm; fruiting pedicels divaricate-ascending; ovules 4-10 (-12) per ovary. Draba sphaeroides
21 Fruits flattened, 2-4.5 mm wide, 10-18-seeded; styles 0.4-0.8(-1) mm; racemes 10-20(-25)-flowered; surface of leaf blades pubescent with (2-) 4-rayed trichomes; se Oregon. Draba cusickii
21 Fruits inflated basally, 3.5-5 mm wide, 8-12-seeded; styles (0.5-)0.7-1.4 mm; racemes 5-10(-16)-flowered; surface of leaf blades pubescent with 2-6-rayed trichomes; Alberta, British Columbia, Colorado, Utah, Wyoming, Yukon. Draba ventosa

Group 9

1 Abaxial surface of leaf blades usually with simple and/or 2-rayed trichomes, rarely glabrous > 2
1 Abaxial surface of leaf blades with simple and 2-6-rayed trichomes, sometimes subdendritic and up to 12-rayed > 8
2 Sepals persistent > 3
2 Sepals caducous > 4
3 Petals yellow, 3.5-5 × 1.5-2 mm; styles 0.4-1 mm; fruiting pedicels 3-7 mm; fruits 2.5-5 mm wide, flattened. Draba longisquamosa
3 Petals white, 1.5-2 × 0.5-0.6 mm; styles 0.1-0.2 mm; fruiting pedicels 1-2.5(-4) mm; fruits (1.2-)1.5-2.5 mm wide, slightly inflated basally. Draba monoensis
4 Abaxial surface of leaf blades glabrous, midvein prominent; plants pulvinate. Draba densifolia
4 Abaxial surface of leaf blades usually pubescent, sometimes glabrous (D. cyclomorpha), midvein usually obscure (except D. subcapitata); plants often not pulvinate > 5
5 Petals 1.4-4 × 0.5-1 mm; racemes 1-8 (or 9)-flowered, not or slightly elongated in fruit; Alaska, Canada, Greenland > 6
5 Petals 4-6 × 1.5-2.5 mm; racemes 4-15(-21)-flowered, elongated in fruit; California, Oregon > 7
6 Petals yellow or yellowish green, linear-oblanceolate, 3-4 × 0.5-0.8 mm; leaf blades each with midvein usually obscured; ovules 4-8 per ovary; Alaska. Draba aleutica
6 Petals white or creamy white, spatulate, 1.5-2(-2.5) × 0.7-1 mm; leaf blades each with midvein strongly thickened; ovules 14-24 per ovary; Alaska, Greenland, Northwest Territories, Nunavut, Quebec. Draba subcapitata
7 Fruits plane, valves glabrous; fruiting pedicels softly pilose; ovules 8-12 per ovary; seeds 1.4-1.9 × 1-1.2 mm; ne Oregon. Draba cyclomorpha
7 Fruits slightly twisted, valves pubescent; fruiting pedicels hirsute; ovules 10-16 per ovary; seeds 1-1.4 × 0.6-1 mm; ec California. Draba lemmonii
8 Racemes not or slightly elongated (sometimes subumbellate) in fruit > 9
8 Racemes elongated in fruit > 13
9 Abaxial surface of leaf blades with 2-5-rayed trichomes; fruit valves glabrous; petals 1-2 mm wide. Draba macounii
9 Abaxial surface of leaf blades with some simple trichomes; fruit valves pubescent or puberulent (sometimes glabrous in D. stenopetala and D. subcapitata); petals 0.3-1.5 mm wide > 10
10 Basal leaves densely imbricate; fruits 3-6 mm, inflated (at least basally) > 11
10 Basal leaves not imbricate; fruits 5-10 mm, flattened > 12
11 Petals usually yellow, rarely purple, linear, 2.5-5 × 0.3-0.7 mm; ovules 4-10 per ovary. Draba stenopetala
11 Petals white or creamy white, spatulate, 1.5-2(-2.5) × 0.7-1 mm; ovules 14-24 per ovary. Draba subcapitata
12 Fruits ovate-elliptic, 2-3.2 mm wide, valves often densely pubescent; ovules (16-)18-28 per ovary; leaf blades with apices obtuse to rounded, surfaces with subcruciform trichomes. Draba micropetala
12 Fruits obovate, (3-)3.5-5 mm wide, valves often glabrate; ovules 8-16 (-20) per ovary; leaf blades with apices acute or subacute, surfaces with simple and/or 2-branched trichomes. Draba pauciflora
13 Plants stoloniferous; basal leaves not rosulate; fruit valves glabrous. Draba ogilviensis
13 Plants cespitose, not stoloniferous; basal leaves rosulate; fruit valves pubescent or glabrous > 14
14 Petals linear, 0.3-0.7 mm wide; fruits inflated basally; ovules 4-10 per ovary. Draba stenopetala
14 Petals obovate, spatulate, or narrowly oblanceolate, (0.7-)1-4.6 mm wide; fruits flattened; ovules 12-36 per ovary > 15
15 Petals white; fruit valves pubescent, trichomes 2-5-rayed; stigmas distinctly wider than styles; abaxial surface of leaf blades with some 6-12-rayed trichomes > 16
15 Petals pale or bright yellow (sometimes creamy white in D. oxycarpa); fruit valves usually pubescent, sometimes glabrous, trichomes simple, spurred, or 2-rayed; stigmas about as wide as styles; abaxial surface of leaf blades with 2-5-rayed trichomes (rays sometimes spurred in D. oxycarpa) > 17
16 Fruits with 2-4-rayed and, sometimes, simple trichomes; petals 3-4 mm; stems proximally with branched trichomes 2-6-rayed. Draba arctogena
16 Fruits with (2-)5-12-rayed trichomes; petals 3.5-5 mm; stems proximally with branched trichomes 4-10-rayed. Draba oblongata
17 Fruiting pedicels 1-3(-4) mm; petals 2-3 × (0.7-)1-1.5 mm; styles 0.05- 0.3 mm; racemes slightly elongated in fruit. Draba micropetala
17 Fruiting pedicels (2.5-)4-13(-30) mm; petals 3.5-6 × 1.7-4.6 mm; styles (0.1-)0.2-0.9 mm; racemes often considerably elongated in fruit > 18
18 Basal leaf blades linear to linear-oblanceolate, 1-2.5(-4) mm wide, midveins prominent. Draba pilosa
18 Basal leaf blades oblong, lanceolate, oblanceolate, or obovate, 2-9 mm wide, midveins obscure > 19
19 Petals 1.7-2.5 mm wide; sepals purplish tinged; fruits elliptic; abaxial surface of leaf blades with 2-4-rayed trichomes; seeds pale brown. Draba alpina
19 Petals 2.5-4.6 mm wide; sepals gray-green; fruits ovate, ovate-oblong, or lanceolate; abaxial surface of leaf blades with 2-5-rayed and subdendritic trichomes; seeds dark brown or black > 20
20 Basal leaf blade margins usually denticulate; fruits ovate to ovate-oblong, 3-5 mm wide; styles 0.2-0.6 mm; Greenland. Draba oxycarpa
20 Basal leaf blade margins entire; fruits lanceolate, 2.3-3.8 mm wide; styles 0.1-0.3 mm; Canada. Draba simmonsii

Group 10

1 Abaxial surface of leaf blades with pectinate, subdendritic, or some 7-12-rayed, stellate trichomes > 2
1 Abaxial surface of leaf blades with 2-6-rayed trichomes > 14
2 Styles 1.5-3(-3.8) mm; seeds winged; anthers 0.7-0.9 mm. Draba pterosperma
2 Styles (0.05-)0.1-1(-1.2) mm; seeds not winged; anthers 0.2-0.7 mm > 3
3 Abaxial surface of leaf blades with some pectinate trichomes > 4
3 Abaxial surface of leaf blades with stellate or subdendritic trichomes > 5
4 Fruits 5-9(-11) mm, flattened; petals 4-6 mm; sepals 2.5-3.5(-4) mm; leaf blades usually with obscure midveins. Draba incerta
4 Fruits 3-6(-7) mm, inflated; petals 2.5-4 mm; sepals 1.5-3 mm; leaf blades with prominent midveins. Draba oligosperma
5 Fruit valves pubescent, trichomes 2-6-rayed > 6
5 Fruit valves glabrous or pubescent to puberulent, trichomes primarily simple and 2-rayed > 9
6 Plants not pulvinate; leaf blades 0.4-2.3(-3) cm × 1-6.5 mm; petals white; ovules 20-42 per ovary > 7
6 Plants pulvinate; leaf blades 0.2-0.8 cm × 0.5-1.5(-2) mm; petals yellow; ovules 4-12(-16) per ovary > 8
7 Basal leaf blades apically with simple trichomes, midveins distinct abaxially; seeds 0.8-1.1 × (0.6-)0.7-0.8 mm. Draba arctica
7 Basal leaf blades apically without simple trichomes, midveins obscure abaxially; seeds 0.6-0.8 × 0.4-0.6 mm. Draba cinerea
8 Fruits inflated basally (symmetric), plane, (2.5-)3-4(-5) mm; Alberta, British Columbia, California, Montana, Utah, Wyoming. Draba novolympica
8 Fruits flattened (asymmetric), twisted or plane, 4-8(-10) mm; ec California. Draba sierrae
9 Seeds 1.5-2.2 × 1-1.4 mm; fruits 3-5 mm wide; styles 0.5-1.2 mm; petals yellow; ovules 8-16 per ovary > 10
9 Seeds 0.7-1.3 × 0.5-0.8 mm; fruits 1-2.5(-3) mm wide (-5 mm wide in D. oxycarpa); styles 0.05-0.6(-1 in D. scotteri) mm; petals white or creamy white (yellow in D. scotteri and, sometimes, D. oxycarpa); ovules (10-) 12-28 per ovary > 11
10 Leaf blades each with prominent midvein; basal blades linear to linear-oblanceolate, 0.8-1.5 mm wide; petals pale yellow; fruits slightly inflated basally; w Montana, nw Wyoming. Draba paysonii
10 Leaf blades each with obscure midvein; basal blades oblanceolate to obovate or suborbicular, 2-4.5 mm wide; petals bright yellow; fruits flattened; Alaska, British Columbia, Washington, Yukon. Draba ruaxes
11 Rachises often slightly flexuous; petals 2-3.5 × 1-1.5 mm; fruits linear to narrowly lanceolate or narrowly oblong, slightly twisted or plane. Draba lonchocarpa
11 Rachises not flexuous; petals 3-5.5 × 1.5-3.5 mm; fruits ovate, oblong, lanceolate, or broadly so, rarely narrowly lanceolate, plane > 12
12 Fruits 3-5 mm wide; fruiting pedicels often curved upwards; leaf blade margins usually denticulate. Draba oxycarpa
12 Fruits 1.5-3 mm wide; fruiting pedicels straight; leaf blade margins usually entire, rarely denticulate (D. lactea) > 13
13 Petals white; fruits 4-8 mm, valves glabrous. Draba lactea
13 Petals yellow; fruits 5-11 mm, valves pubescent. Draba scotteri
14 Ovules (16-)18-36 per ovary > 15
14 Ovules 4-14(-16) per ovary > 20
15 Styles (0.8-)1.2-3.5 mm; racemes 12-43-flowered; s California. Draba saxosa
15 Styles 0.01-0.7 mm; racemes 2-12(-23)-flowered; Alaska, Canada, Greenland > 16
16 Fruits linear to linear-elliptic, (8-)10-17(-20) × 1.5-2 mm; plants not cespitose, caudex simple. Draba stenoloba
16 Fruits oblong, ovate, or lanceolate, 4-12 × 2-5.5 mm; plants often cespitose, caudex branched > 17
17 Leaf blade margins entire > 18
17 Leaf blade margins dentate or denticulate > 19
18 Petals 4-6 × 3-5 mm; fruits 3.5-5.5 mm wide (stigmas distinctly wider than styles); racemes not elongated (corymbose) in fruit. Draba corymbosa
18 Petals 2-3 × (0.7-)1-1.5 mm; fruits 2-3.2 mm wide (stigmas narrower than styles); racemes mostly elongated in fruit. Draba micropetala
19 Fruits oblong to lanceolate-elliptic, 4-8 × 2-3 mm; fruiting pedicels straight, suberect to ascending, often subappressed to rachises; petals white, 2.5-4 mm. Draba norvegica
19 Fruits ovate to ovate-oblong, 5-10 × 3-5 mm; fruiting pedicels curved upwards, subhorizontal to divaricate-ascending, not appressed to rachises; petals yellow or creamy white, 3.5-5 mm. Draba oxycarpa
20 Fruits inflated (at least basally), usually ovoid, subglobose, or ellipsoid, rarely lanceolate > 21
20 Fruits flattened, ovate, lanceolate, oblong, or elliptic > 25
21 Leaf blades (1-)2-4(-6) mm wide; fruit valves glabrous or pubescent, trichomes simple and 2(-4)-rayed > 22
21 Leaf blades 0.5-1.5 mm wide; fruit valves pubescent, trichomes 2-6-rayed > 23
22 Racemes 3-10(-13)-flowered; fruiting pedicels horizontal to divaricate, curved, glabrous (at least adaxially); ovules 10-16 per ovary; Alaska, Alberta, British Columbia, Montana, Yukon. Draba macounii
22 Racemes (5-)9-18(-23)-flowered; fruiting pedicels divaricate-ascending, usually straight, rarely curved, pubescent; ovules (4-)8-12 per ovary; sc Utah. Draba sobolifera
23 Adaxial surface of leaf blades with simple and 4-6-rayed trichomes; fruit valves with 4-rayed trichomes (some rays spurred). Draba trichocarpa
23 Adaxial surface of leaf blades with simple and 2-rayed trichomes; fruit valves with 2-6-rayed and simple trichomes > 24
24 Fruits (2.5-)3-4(-5) × 1.5-3.5 mm; petals bright yellow, 2-3.5(-4) mm; styles 0.2-0.6(-0.8) mm. Draba novolympica
24 Fruits (5-)6-9 × (3-)3.7-5 mm; petals pale yellow, (4-)5-6 mm; styles (0.6-)0.8-1.2 mm. Draba paysonii
25 Abaxial surface of leaf blades with only 2-rayed trichomes. Draba lemmonii
25 Abaxial surface of leaf blades glabrous or with 2-4-rayed and simple trichomes > 26
26 Adaxial surface of leaf blades pubescent with simple and 2-4-rayed trichomes > 27
26 Adaxial surface of leaf blades glabrous (at least proximally), usually pubescent distally with simple trichomes > 29
27 Styles (0.8-)1.2-3.5 mm; petals linear-oblanceolate, 0.5-1 mm wide; racemes 12-43-flowered; s California. Draba saxosa
27 Styles 0.2-0.9(-1.1) mm; petals obovate, 2-3.5 mm wide; racemes 2-10 (-14)-flowered; Alaska, Canada, Greenland, Washington > 28
28 Racemes (corymbose) not or slightly elongated in fruit; fruits 6-12 mm; seeds 1-1.3 × 0.6-0.9 mm. Draba corymbosa
28 Racemes elongated in fruit; fruits 4-8(-10) mm; seeds 1.5-2 × 1-1.3 mm. Draba ruaxes
29 Styles 0.3-0.6(-1) mm; petals pale yellow, 2-5 mm; leaf blades each with prominent midvein. Draba densifolia
29 Styles (0.8-)1-4.5 mm; petals white, 4.5-6.5 mm; leaf blades each with obscure midvein > 30
30 Styles (0.8-)1-1.7(-2) mm; leaf blades oblong-linear to narrowly oblanceolate, 1-2 mm wide; anthers ovate, 0.5-0.6 mm; c Idaho. Draba hitchcockii
30 Styles (1.2-)2-4(-4.5) mm; leaf blades oblanceolate to obovate, 1.5-3.5 mm wide; anthers oblong, 0.8-1 mm; s Nevada. Draba jaegeri
... more about "Draba"
Ihsan A. Al-Shehbaz +, Michael D. Windham +  and Reidar Elven +
Linnaeus +
North America +, Mexico +, South America (Andes +, Colombia to Patagonia) +, Europe +, Asia +, nw Africa +, alpine and boreal +  and rarely in temperate and low-elevation areas of North America and Eurasia. +
Greek drabe, acrid, for taste of mustard plant +
beilstein2003a +, ekman1929a +, ekman1930a +, ekman1931a +, ekman1932a +, fernald1934a +, hitchcock1941a +, koch2002a +, mulligan1976a +, payson1917a +  and schulz1927a +
Abdra +, Erophila +, Nesodraba +  and Tomostima +
Brassicaceae tribe Arabideae +