Common Name: Watercress

General Information

Nasturtium officinale is a very succulent, aquatic, perennial plant with stems that can be 50cm or more long.
The plant is a fairly well-known salad crop, often gathered from the wild but also grown commercially and sold in markets. It is also seen as a very healthy, vitamin and mineral rich food and, as such, has gained a reputation for its medicinal uses.
Nasturtium officinale is widespread with stable populations and does not face any major threats.The plant is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2019)[].
Nasturtium officinale is often cultivated in many areas of the world as a food crop. It spreads quickly and even small stem sections, when separated from the parent plant, will readily produce new roots and become new plants. The plant has escaped from cultivation in many areas, it is reported to be a serious river-weed in New Zealand[].

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[, ]. Cooking the leaves, however, will destroy any parasites and render the plant perfectly safe to eat[].

Botanical References

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Range

Eurasia - Sweden, British Isles and Portugal, east to Kazakhstan, western Himalayas and Afghanistan; N. Africa - Morocco to Egypt and Ethiopia

Habitat

Stream margins, ditches, flushes etc with moving water[, ], usually in chalk or limestone areas[].

Properties

Weed Potential	Yes
Conservation Status	Least Concern
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Perennial
Height	0.50 m
Growth Rate	Fast
Pollinators	Bees, Flies, Self
Self-fertile	Yes
Cultivation Status	Cultivated, Wild

Cultivation Details

Watercress is a plant of the temperate zone, but it can be cultivated in the tropics at elevations between 1,000 - 3,000 metres. It grows best in areas where annual daytime temperatures are within the range 12 - 17°c, but can tolerate 6 - 32°c[]. When dormant, the plant can survive temperatures down to about -15°c[]. It prefers a mean annual rainfall in the range 1,000 - 2,300mm, but tolerates 300 - 4,200mm[].
Watercress is easily grown when given the correct conditions of full sun in slowly flowing clean water, preferably coming from chalky or limestone soils[]. It prefers to grow in water about 5cm deep[] with an optimum pH 7.2[]. Plants can be grown in wet soil if the position is somewhat shaded and protection is given in winter, though the flavour may be hotter[, ]. Prefers a pH in the range 6.5 - 7.5, tolerating 4.5 - 8.3[].
The plant has become a serious river-weed in New Zealand[].
A first harvest may be taken 30 - 45 days after planting out, and it may thereafter be harvested every 40 - 80 days[].
Yields can be as high as 50 tonnes per hectare[].
Watercress is often cultivated for its edible leaves, there are some named varieties[, ]. The plant is very sensitive to pollution so a clean source of water is required[]. Plants will often continue to grow all through mild winters. A fast-growing plant, the stems trail along the ground or float in water and produce new roots at the leaf nodes, thus making the plant very easy to propagate vegetatively[]. Unfortunately, virus diseases have become more common in cultivated plants and so most propagation is carried out by seed[].
This is a diploid species. It has hybridised naturally in the wild with the triploid species N. Microphyllum to produce the sterile hybrid N. X sterilis which is also commonly cultivated as a salad crop[].
The flowers are a rich source of pollen and so are very attractive to bees[].

Edible Uses

Leaves - raw or cooked[, , , , , ]. Water cress is mainly used as a garnish or as an addition to salads, the flavour is strong with a characteristic hotness[]. It has a reputation as a spring tonic, and this is its main season of use in the temperate zone, though it can be harvested for most of the year and can give 10 pickings annually[]. 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[]. A nutritional analysis is available[].

The seed can be sprouted and eaten in salads[]. A hot mustardy flavour[].

The seed is ground into a powder and used as a mustard[, ]. 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[].

Medicinal

Watercress is very rich in vitamins and minerals, and has long been valued as a food and medicinal plant[]. Considered a cleansing herb, its high content of vitamin C makes it a remedy that is particularly valuable for chronic illnesses[].

The leaves are antiscorbutic, depurative, diuretic, expectorant, purgative, hypoglycaemic, odontalgic, stimulant and stomachic[, , , , , , ]. The plant has been used as a specific in the treatment of TB[]. 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[]. Applied externally, it has a long-standing reputation as an effective hair tonic, helping to promote the growth of thick hair[]. A poultice of the leaves is said to be an effective treatment for healing glandular tumours or lymphatic swellings[]. Some caution is advised, excessive use of the plant can lead to stomach upsets[, ]. The leaves can be harvested almost throughout the year and are used fresh[].

Other Uses

The juice of the plant is a nicotine solvent and is used as such on strong tobaccos[].

Propagation

Seed - sow spring in a pot emmersed to half its depth in water. Germination should take place within a couple of weeks. Prick out seedlings into individual pots whilst they are still small and increase the depth of water gradually until they are submerged. Plant out into a pond in the summer.
Cuttings can be taken at any time in the growing season. Virtually any part of the plant, including a single leaf, will form roots if detached from the parent plant[]. Just put it in a container of water until the roots are well formed and then plant out in shallow water.