Biennials or perennials; (stoloniferous or simple or several from caudex); not scapose; (often glaucous). Stems erect or decumbent, unbranched or branched distally. Leaves basal and cauline; petiolate or sessile; basal rosulate, petiolate, margins entire, denticulate, or dentate; cauline blade (base auriculate or subamplexicaul [sagittate]), margins entire or dentate. Racemes (corymbose, several-flowered), considerably elongated or congested in fruit. Fruiting pedicels horizontal or, rarely, ascending, slender. Flowers: sepals erect, oblong, or ovate [obovate]; petals white, pink, or purple, spatulate [obovate, oblanceolate, oblong, or, rarely, broadly linear], (longer than sepals), claw obscurely differentiated from blade, (apex obtuse or rounded); stamens slightly tetradynamous; filaments not dilated basally; anthers ovate [oblong], (apex obtuse); nectar glands lateral, 2 and subtending stamens, or 4 and 1 on each side of stamen. Fruits sessile, obcordate, obovate, obdeltate, elliptical, or oblong, smooth, strongly angustiseptate, (winged or not winged apically); valves each obscurely to prominently veined, strongly keeled; replum rounded; septum complete; ovules 4–14[–24] per ovary; style included in, or much exceeding, apical notch; stigma capitate. Seeds plump or slightly compressed, not winged, ovoid [oblong]; seed coat (longitudinally, minutely reticulate to nearly smooth), not mucilaginous when wetted; cotyledons accumbent. x = 7.

Distribution

North America, Mexico, South America (Patagonia), Europe, Asia, n Africa.

Discussion

Species ca. 80 (3 in the flora).

Previous North American accounts (e.g., E. B. Payson 1926; P. K. Holmgren 1971; R. C. Rollins 1993) treated species of Noccaea as members of Thlaspi. As discussed under the latter genus (see references there) and as shown by M. Koch and I. A. Al-Shehbaz (2004), Noccaea is definitely distinct from Thlaspi. Excellent comments on the biology, variability, and distribution of the North American taxa were given by Holmgren and are not repeated here.

Selected References

Holmgren, P. K. 1971. A biosystematic study of North American Thlaspi montanum and its allies. Mem. New York Bot. Gard. 21(2): 1–106.

Koch, M. and I. A. Al-Shehbaz. 2004. Taxonomic and phylogenetic evaluation of the American “Thlaspi” species: Identity and relationship to the Eurasian genus Noccaea (Brassicaceae). Syst. Bot. 29: 375–384.

Lower Taxa

Noccaea arctica, Noccaea fendleri, Noccaea parviflora

Key

1	Petals not flaring between blade and claw, 2-2.8(-3.6) mm; styles (0.2-)0.3-0.5(-0.6) mm; sepals (1-)1.3-1.8(-2.2) mm.	Noccaea parviflora
1	Petals often flaring between blade and claw, 3-13 mm; styles (0.3-)0.6-4.2 mm; sepals 1.5-5.3 mm	> 2
2	Styles (0.3-)0.6-1 mm; fruits not winged apically; petals 3-5 mm; arctic Alaska, Yukon.	Noccaea arctica
2	Styles (0.4-)1.1-4.2 mm; fruits usually winged, rarely not winged apically; petals (3.4-) 4.2-13 mm; Pacific and Mountain states.	Noccaea fendleri