Watercress

Nasturtium officinale

Physical Characteristics

Nasturtium officinale is a PERENNIAL growing to 0.5 m (1ft 8in) by 1 m (3ft 3in) at a fast rate. See above for USDA hardiness. It is hardy to UK zone 6 and is not frost tender. It is in flower from May to October, and the seeds ripen from July to October. The species is hermaphrodite (has both male and female organs) and is pollinated by Bees, flies. The plant is self-fertile. It is noted for attracting wildlife. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils. It cannot grow in the shade. It prefers wet soil and can grow in water.

Distribution

Europe, including Britain, from Sweden and Denmark south and east to N. Africa and W. Asia.

Habitats

Pond; Bog Garden;

Edible Uses

Edible Parts: Leaves Seed Edible Uses: Condiment Leaves - raw or cooked[2, 5, 7, 9, 16, 27]. Water cress is mainly used as a garnish or as an addition to salads, the flavour is strong with a characteristic hotness[183]. It has a reputation as a spring tonic, and this is its main season of use, though it can be harvested for most of the year and can give 10 pickings annually[238]. Some caution is advised if gathering the plant from the wild, see the notes above on toxicity. The leaves are exceptionally rich in vitamins and minerals, especially iron[200]. A nutritional analysis is available[218]. The seed can be sprouted and eaten in salads[183]. A hot mustardy flavour[K]. The seed is ground into a powder and used as a mustard[46, 183]. The pungency of mustard develops when cold water is added to the ground-up seed - an enzyme (myrosin) acts on a glycoside (sinigrin) to produce a sulphur compound. The reaction takes 10 - 15 minutes. Mixing with hot water or vinegar, or adding salt, inhibits the enzyme and produces a mild but bitter mustard[238].

Medicinal Uses

Antirheumatic Antiscorbutic Appetizer Depurative Diuretic Expectorant Hypoglycaemic Miscellany Odontalgic Purgative Stimulant Stomachic TB Vitamin C Watercress is very rich in vitamins and minerals, and has long been valued as a food and medicinal plant[254]. Considered a cleansing herb, its high content of vitamin C makes it a remedy that is particularly valuable for chronic illnesses[254]. The leaves are antiscorbutic, depurative, diuretic, expectorant, purgative, hypoglycaemic, odontalgic, stimulant and stomachic[4, 7, 9, 21, 46, 222, 238]. The plant has been used as a specific in the treatment of TB[4]. The freshly pressed juice has been used internally and externally in the treatment of chest and kidney complaints, chronic irritations and inflammations of the skin etc[9]. Applied externally, it has a long-standing reputation as an effective hair tonic, helping to promote the growth of thick hair[244]. A poultice of the leaves is said to be an effective treatment for healing glandular tumours or lymphatic swellings[244]. Some caution is advised, excessive use of the plant can lead to stomach upsets[9, 21]. The leaves can be harvested almost throughout the year and are used fresh[238].

Known Hazards

Whilst the plant is very wholesome and nutritious, some care should be taken if harvesting it from the wild. Any plants growing in water that drains from fields where animals, particularly sheep, graze should not be used raw. This is due to the risk of it being infested with the liver fluke parasite[5, 244]. Cooking the leaves, however, will destroy any parasites and render the plant perfectly safe to eat[244]. May inhibit the metabolism of paracetamol [301].