- Name also: Winter Cress, Common Winter-cress, Yellow Rocket, Herb Barbara, Yellow Rocketcress, Winter Rocket, Wound Rocket, Garden Yellowrocket
- Family: Mustard Family – Brassicaceae (Cruciferae)
- Growing form: Biennial or perennial herb.
- Height: 30–60 cm (12–25 in.). Stem upper part branching, bristly, glabrous.
- Flower: Corolla regular (actinomorphic) (quite often malformed, small), bright yellow, approx. 1 cm (0.4 in.) wide; petals four, 6–8 mm (0.24–0.32 in.) long. Sepals 4, clearly shorter than petals. Stamens 6, of which 4 long and 2 short. Gynoecium fused, a single carpel. Inflorescence a raceme, elongating in fruiting stage. Buds glabrous.
- Leaves: In basal rosette and alternate on stem, rosette leaves stalked, uppermost stem leaves stalkless, amplexicaul. Blade glabrous, lowest leaves’ leaflets in 2–5 pairs with wedge-shaped terminal lobe, blade of uppermost stem leaves virtually lobeless, large-toothed. Rosette leaves hairy at end of summer.
- Fruit: Many-seeded, curved (sometimes straight), 4-edged, 1.5–2.5(–3) cm (0.6–1(–1.2) in.) long, siliqua spreading, ascending oblique, tip with approx. 2–3 mm (0.08–0.12 in.) long bristle. Stalk approx. 4–7 mm, spreading, glabrous.
- Habitat: Hay fields, banks, roadsides, ditch banks, rocky outcrops, stony slopes, waste ground.
- Flowering time: May–June.
Nowadays it is quite usual to drive past wintercress stands that stretch along roadsides for several kilometres, and it is quite a refreshing sight. The plant has taken a long time to be accepted as a Finnish plant: it was only discovered for the first time in the 1840s and began to spread in earnest at the end of the century. Its victory parade began when traditional grazing land was given over to the cultivation of hay and sowing seed was imported from abroad. Wintercress produces up to 10,000 seeds per plant, and they are very similar to hay and clover seed with regards to both size and weight so they spread well with them. In northern Finland the plant is still rare – so far.
Wintercress’s overwintering rosette leaves have been eaten in days of yore during the long northern winter to ward off scurvy. There is nothing to stop plants that have been pulled from the vegetable patch as weeds being used in the kitchen like lettuce or spinach. The flavour is close to that of garden cress or watercress with a slight tang of lemon. Wintercress began to be used as chicken feed, for which it was well suited. Members of the genus have been popular winter vegetables, so its scientific name comes from St Barbara, whose feast day is held during the winter. St Barbara was the patron saint of gunners, miners and stonebreakers, and her plants were used to help heal the wounds of those that she protected, whose work made them vulnerable to cuts.
Wintercress resembles many of the other large annual yellow-flowered members of its family such as wild mustard, wild turnip and wild radish, although it is clearly sturdier and usually perennial. It flowers at the end of May when many of the other annuals that share its habitat are still shoots. It can be differentiated from its close relative small-flowered wintercress (B. stricta), mainly by the way that the latter’s siliquae grow flush with the stem, and its corolla is only slightly longer than its calyx.