Draba reptans

Annuals; scapose or subscapose. Stems (simple or few from, or distal to, base), unbranched, (0.1–)0.3–1.2(–1.6) dm, sparsely to densely pubescent proximally, trichomes 2 (or 3)-rayed, 0.1–0.6 mm, sometimes with simple or spurred ones, to 0.9 mm, distally usually glabrous, rarely with few trichomes. Basal leaves not rosulate; petiole obscure; blade elliptic or spatulate to obovate or suborbicular, 0.5–2.3(–3) cm × 1.5–8(–13) mm, margins entire, surfaces pubescent abaxially with stalked, 2–4-rayed trichomes, 0.1–0.5 mm, adaxially with simple trichomes, 0.6–1 mm, with stalked, 2-rayed ones, to 0.7 mm. Cauline leaves usually 0, rarely 1–3; sessile; blade similar to basal. Racemes (3–)5–12(–16)-flowered, ebracteate, (subumbellate), not elongated in fruit; rachis not flexuous, usually glabrous, rarely sparsely pubescent. Fruiting pedicels horizontal to divaricate-ascending, straight, (1–)2–7(–9) mm, glabrous or glabrate. Flowers: (late-season ones cleistogamous, apetalous); sepals oblong, 1.5–2.3 mm, pubescent, (trichomes simple); petals (rarely absent), white, spatulate, 2–4.5 × 1–1.5 mm; anthers ovate, 0.4–0.5 mm. Fruits linear to linear-oblong, plane, flattened, (5–)7–16(–20) × 1.2–2.3 mm; valves glabrous or pubescent, trichomes usually simple and antrorse, 0.1–0.3 mm, rarely with fewer, spurred or 2-rayed ones; ovules 32–88 per ovary; style 0.02–0.1 mm. Seeds oblong to ovoid, 0.5–0.8 × 0.3–0.5 mm. 2n = 16, 30, 32.

Phenology: Flowering Feb–Jun(-Aug).
Habitat: Rock outcrops, dry slopes and hillsides, prairies, glades, roadsides, disturbed sites
Elevation: 0-3000 m

Distribution

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Alta., B.C., Man., Ont., Sask., Ala., Ariz., Ark., Calif., Colo., Ga., Idaho, Ill., Iowa, Kans., Mass., Mich., Minn., Mo., Mont., Nebr., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., S.C., S.Dak., Tenn., Tex., Utah, Wash., Wis., Wyo.

Discussion

Draba reptans is often confused with D. cuneifolia, but the two are easily separated. The rachises and pedicels of D. reptans are usually glabrous (rarely with a few isolated trichomes); those of D. cuneifolia are always densely pubescent. Interestingly, both species show parallel variations in chromosome number; it is currently unclear whether this variation is real or the result of misidentified specimens and/or erroneous counts.

Selected References

None.

Lower Taxa

None.