Watercress (Rorippa nasturtium-aquaticum, R. microphylla) are fast-growing, aquatic or semi-aquatic, perennials native from Europe to central Asia and one of the oldest known leaf vegetables consumed by human beings. These plants are members of the Family Brassicaceae or cabbage family, botanically related to garden cress and mustard — all noteworthy for a peppery, tangy flavor.

The stems of watercress are floating and the leaves are pinnately compound. Watercress produces small, white and green flowers in clusters.

Nasturtium officinale Ait. f. and Sisymbrium nasturtium-aquaticum L. are synonyms of R. nasturtium-aquaticum. Nasturtium officinale var microphyllum (Boenn. ex Reich.) Thellung is a synonym of R. microphylla (ITIS, 2004). Although often listed as species in the genus Nasturtium, watercress are not related to the flowers in the genus Tropaeolum (Family Tropaeolaceae), popularly known as "nasturtiums".

Watercress cultivation

Cultivation of watercress is practical on both a large scale and a garden scale. Being semi-aquatic, watercress is well-suited to hydroponic cultivation, thriving best in water that is slightly alkaline. In many local markets the demand for hydroponically-grown watercress exceeds supply. This is due in part to the fact that cress leaves are unsuitable for distribution in dried form and can only be stored for a short period. If unharvested, watercress can grow to a height of 50-120 cm. Also sold as sprouts: the edible shoots harvested just days after germination.

Food value

Watercress contains significant amounts of iron, calcium and folic acid, in addition to vitamins A and C. In some regions watercress is regarded as a weed, in other regions as an aquatic vegetable or herb. Where watercress is grown in the presence of animal waste, it can be a haven for parasites such as the liver fluke.

Many benefits from eating watercress are claimed, such as that it acts as a mild stimulant, a source of phytochemicals and antioxidants, a diuretic, an expectorant, and a digestive aid.

Reference

• ITIS (home page) (visited October 2004)