Annual herb with a taproot 10 - 40 cm tall Flowers: in a branched cluster, stalked, white, 2 - 3 mm long. Sepals four, green. Petals four, longer than sepals. Stamens six. Fruit: a narrow pod, upright on an ascending stalk, 1.5 - 2.5 cm long. Stems: multiple, upright, typically unbranched, green or sometimes purplish, round in cross-section. Basal leaves: numerous, usually in a rosette, pinnately divided, persistent, sometimes shallowly few-lobed. Terminal leaflet rounded to kidney-shaped. Stem leaves: two to five, alternate, pinnately divided, stalked. Leafstalks with a fringe of hairs, usually at base. Lateral leaflets reverse egg-shaped to oblong to linear- spatula-shaped, with one or two teeth along the margins, usually hairy above.
Similar species: The similar Cardamine parviflora, C. parviflora var. arenicola, and C. pensylvanica differ by not having a marginal fringe of hairs at the base of the leafstalks (on stem leaves).
Flowering: mid-April to early June
Habitat and ecology: Introduced from Europe. A common weed found in cultivated ground. Has also been found in waste ground and along railroads.
Occurence in the Chicago region: non-native
Etymology: Cardamine comes from the Greek word kardamon, which refers to plants in the cress family. Hirsuta means hairy.
Annual with glabrous stems 1-4 dm; basal lvs numerous and conspicuous in comparison with the few small stem-lvs, the pl appearing subscapose; terminal lfl of basal lvs rotund to reniform, entire to shallowly few-lobed; petioles of the cauline lvs ciliate at least at base; lateral segments of the cauline lvs gradually narrower toward the top of the stem, obovate-oblong to linear-spatulate, often with 1 or 2 teeth, commonly hirsutulous above; pet white, 2-3 mm; pedicels narrowly ascending; frs erect, 1.5-2.5 cm; 2n=16. Widely distributed in the Old World; naturalized in moist, especially sandy soil from s. N.Y. to Ill. and Ala. Mar., Apr.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.