- Name also: Small-flowered Yellow Rocket
- Family: Mustard Family – Brassicaceae (Cruciferae)
- Growing form: Biennial herb.
- Height: 40–80 cm (16–32 in.). Stem bristly, glabrous, base purple.
- Flower: Corolla regular (actinomorphic), pale yellow, approx. 0.5 cm (0.2 in.) wide; petals 4, with round or notched tips, 3–4 mm (0.12–0.16 in.) long. Sepals 4, slightly shorter than petals. Stamens 6, of which 4 long and 2 short. Gynoecium fused, a single carpel. Inflorescence a raceme, extending in fruiting stage. Buds hairy.
- Leaves: Basal rosette and alternate on stem, rosette leaves stalked, stalk with ciliate margins, uppermost stem leaves stalkless, amplexicaul. Blade glabrous, lowest leaves with 1-2 pairs leaflets and large terminal lobe, stem leaf-blades quite lobeless, large-toothed. Rosette leaf-blades’ underside commonly bluish or reddish.
- Fruit: Many-seeded, 4-edged, 2–3 cm (0.8–1.2 in.) long siliqua, parallel to stem, tipped with 1–1.5 mm (0.04–0.06 in.) long bristle. Stalk 2–4 mm (0.08–0.16 in.), erect.
- Habitat: Shores of stony and gravelly lakes, rivers and seas, ditches, damp paths, roadsides, meadows, sometimes waste ground.
- Flowering time: June–July.
Small-flowered wintercress is a representative of Finland’s native vegetation on wet stone and gravel-based beaches from the southernmost islets to the rocky shores of Inarijärvi and the banks of River Tenojoki in the north. The species tends to favour nitrogenous soil and can grow on e.g. kelp banks. It does not appear to be completely lacking from any part of the country although suitable habitats can be few and far between in some areas. The species is a weak competitor and is not abundant anywhere, but drainage and construction have created new places for it to grow beside people. Small-flowered wintercress is biennial, so the size and location of its stands varies. In its first year the plant only grows a leaf rosette, then in its second year it grows its stalk. Its scientific name stricta, ‘stiff’, is a description of its rigid, erect and almost unbranched stem.
Small-flowered wintercress’s relative wintercress (B. vulgaris) arrived with people and quickly became common at the end of the 19th century with the cultivation of hay. Several other wintercress species can be found as rare casual aliens. Small-flowered wintercress can be most easily differentiated from wintercress by its erect siliquae which run close to the stalk: wintercress’s fruits are spreading. Small-flowered wintercress’s petals are also smaller than its relative’s, hardly any longer than its sepals. Wintercress’s main inflorescence opens at the beginning of June, while small-flowered wintercress only blooms after midsummer. It is also possible to tell the species apart when they are not in flower because small-flowered wintercress’s rosette leaf-blades are largely formed of large terminal lobes.