Cardamine hirsuta aka Common Bittercress

Cardamine hirsuta, or hairy bittercress, belongs to the mustard family. This fast-growing annual often acts as a garden weed. Its native range spans temperate and subtropical Northern Hemisphere regions. It also reaches tropical mountains in the Old World. It is native to Britain and Ireland. People have introduced it across many other continents. It grows in lawns, gardens, paving cracks, and disturbed ground.

Plants form low rosettes with thin, upright, branching green stems. NC State gives heights of 0.25–0.83 feet [0.08–0.25 metres]. RHS lists a taller range, reaching 1.64 feet [0.5 metres]. Spread is about 0.25–0.5 feet [0.08–0.15 metres]. The roots are shallow and fibrous. Green, pinnate leaves have rounded leaflets and a larger end leaflet. Their edges have lobes and shallow teeth. Leaves and stems may bear small hairs or feel smooth.

Tiny white flowers form clusters above the leaf rosette. Each flower has four petals set in a cross. NC State places flowering from late April into early June. RHS reports flowers through spring, summer, autumn, and mild winters. Narrow seed pods stand upright beside the flowers. They turn reddish brown as they mature. Dry pods burst and throw seeds about 3 feet [0.9 metres]. One plant may make 600–1,000 seeds. Several generations can grow within a single season.

Grow it in sun or part shade with moist soil. It accepts clay, loam, sand, and chalk. It also tolerates acid, neutral, and alkaline soils. RHS lists both good and poor drainage as suitable. Its UK hardiness rating is H7. NC State lists USDA zones 4a–8b. Seeds often sprout in autumn, with plants flowering after winter. Its short life cycle can take about twelve weeks.

Leaves and flowers are edible, either raw or cooked. They add a peppery taste to salads and cooked greens. The flowers can be tough to chew. PFAF records no known hazards or medicinal uses. Flowers offer nectar and pollen to bees and early butterflies. Caterpillars of some butterflies also feed on the plant. RHS suggests it for wildlife and informal gardens. Yet heavy seed production can make it hard to contain. Pull or hoe unwanted plants before they flower. Mulch helps limit its spread in garden beds. No pruning is needed, and disease problems are uncommon. Flea beetles, aphids, whiteflies, and mites may occur.