Lepidium didymum aka Lesser Swine Cress

Lepidium didymum is a small plant in the mustard family, Brassicaceae. Gardeners may know it as lesser swine cress or wart cress. The name Coronopus didymus refers to the same species. Its native range runs from Peru to Brazil and southern South America. It is not native to Britain or Ireland. It now grows across much of Europe and North America. Its spread also reaches parts of Africa and Asia.

This annual or biennial reaches about 1 foot (0.3 metres) tall. One source gives a spread of 0.7 feet (0.2 metres). It first forms a basal rosette, which lasts only briefly. A few to several stems then branch from the plant. These may creep along the ground or rise upward. Stems can reach 1.3 feet (0.4 metres) long. All parts give off a smell that many find unpleasant.

Flowers appear from July to September, according to Plants For A Future. Seeds ripen from August to October in that account. Each flower has both male and female organs. The plant is self-fertile and can pollinate itself. Birds, mammals and human activity help carry its seeds elsewhere. This has helped it spread far beyond its native range. It remains a weed whose range continues to grow.

It grows on roadsides, waste ground and in cultivated fields. It also occurs in gardens, pastures and lawns cut often. Records place it at heights up to 3,281 feet (1,000 metres). It grows mainly in sandy soils in Texas. Cultivation guidance allows sand, loam and clay, with moist soil preferred. It accepts mildly acid, neutral and mildly alkaline ground. Full sun or light shade suits it. Seeds can be sown where they will grow in spring or autumn.

People gather the leaves from wild plants for food. They eat them raw or cooked for their sharp, cress-like taste. People also collect the plant for local medicinal use. Dried material is sold for this purpose in South America. These reports describe use, rather than proving a health benefit. The plant may also have value in soil cleanup projects. Its widespread weed habit matters more in gardens than ornamental use. Plants For A Future lists no known hazards. Another source warns that cows eating it may produce unpleasant-tasting milk. That warning does not establish toxicity to people or pets.