Nasturtium officinale (watercress)
- Summary of Invasiveness
- Taxonomic Tree
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Habitat List
- Biology and Ecology
- Notes on Natural Enemies
- Means of Movement and Dispersal
- Economic Impact
- Environmental Impact
- Social Impact
- Uses List
- Detection and Inspection
- Similarities to Other Species/Conditions
- Prevention and Control
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Nasturtium officinale R. Br.
Preferred Common Name
Other Scientific Names
- Nasturtium nasturtium-aquaticum (L.) H. Karst. nom. inval.
- Radicula nasturtium Cav.
- Radicula nasturtium-aquaticum (L.) Rendle & Britten
- Rorippa nasturtium Beck
- Rorippa nasturtium-aquaticum (L.) Hay.
- Sisymbrium nasturtium Thunb.
- Sisymbrium nasturtium-aquaticum L.
International Common Names
- Spanish: berro; berro de agua
- French: cresson; cresson de fontaine; cresson d'eau
- Chinese: dou ban cai; shui tian jie
- Portuguese: agriao-silvestre
Local Common Names
- Germany: Brunnenkresse; Echte Brunnenkresse; Gemeine Brunnenkresse
- Indonesia: selada air
- Italy: crescione; crescione acquatico; crescione di fonte; nasturzio aquatico; Sisimbrio aquatico
- Japan: mizu garashi; oranda garashi
- Korea, Republic of: mul naeng ee
- Netherlands: witte waterkers
- Poland: rukiew wonda
- Portugal: agriao
- Russian Federation: kreson; kreson vodianoi
- Sweden: kaellkrasse; vattendrasse
- Thailand: phak kaat naam
- Vietnam: xa lack xoong
- NAAOF (Nasturtium officinale)
Summary of InvasivenessTop of page
N. officinale is an emergent aquatic plant growing in fresh water. It is apparently native to much of European and Asian countries, stretching from the British Isles probably as far as western China. It has been deliberately introduced as a leafy vegetable to east and southeast Asia, sub-Saharan Africa, the Americas and the Caribbean, Australia, New Zealand and Pacific islands. N. officinale is now found as a fast-growing environmental weed in parts of North America, Australasia and southern Africa. In some of these regions it has spread to invade waterways and swamp existing native vegetation, and it may smother native communities, altering their structure and composition.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Plantae
- Phylum: Spermatophyta
- Subphylum: Angiospermae
- Class: Dicotyledonae
- Order: Capparidales
- Family: Brassicaceae
- Genus: Nasturtium
- Species: Nasturtium officinale
DescriptionTop of page
Plants are glabrous throughout or sparsely pubescent. Stems 10-110 (-120) cm. Cauline leaves: petiole not winged, base auriculate; blade 3-9(-13)-foliolate, (1-) 2-15(-22) cm; lateral leaflets sessile or petiolulate, rachis not winged, blade smaller than terminal; terminal leaflet (or simple blade) suborbicular to ovate, or oblong to lanceolate, (0.4-)1-4(-5) cm × (3-)7-25(-40) mm, base obtuse, cuneate, or subcordate, margins entire or repand, apex obtuse. Fruiting pedicels divaricate or descending, straight or recurved, 5-17(-24) mm. Flowers: sepals 2-3.5 × 0.9-1.6 mm; petals white or pink, spatulate or obovate, 2.8-4.5(-6) × 1.5-2.5 mm, (base to 1 mm), apex rounded; filaments 2-3.5 mm; anthers 0.6-1 mm. Fruits (0.6-)1-1.8(-2.5) cm × (1.8-)2-2.5(-3) mm; ovules (28-)36-60 per ovary; style 0.5-1(-1.5) mm. Seeds biseriate, reddish brown, ovoid, (0.8-)0.9-1.1 (-1.3) × (0.6-)0.7-0.9(-1) mm, coarsely reticulate with 25-50(-60) areolae on each side (Al-Shehbaz, 2014).
Perennial, aquatic or semi-aquatic herb, prostrate with creeping or floating stems. Stems are hollow, angular to 10-60 cm long, erect to ascending or creeping, from taproot and fibrous roots, often rooting at nodes, then ascending or floating.
Leaves, alternate, dark green to bronze, pinnate. Leaflets usually 3-7, ovate to broadly oblong, terminal leaflet usually larger than laterals. Petiole partially clasping the stem.
Inflorescence consists of compact terminal racemes, rapidly elongating in fruit. Flowers are hermaphrodite and insect pollinated with four petals, free, white, clawed, and glabrous. Limb rounded at apex, 3 mm long, 2 mm broad. Six stamens, with four long and two short. Filaments purplish, glabrous, 3.5 mm long. Anthers yellow. Ovary purplish-green, 2.5 mm long, glabrous. Stigma two-lobed, capitate. Four sepals, free, glabrous or with a few strigose hairs at apex, 3 mm long. Siliqua 13-25 mm long, glabrous, many seeded. Seeds in two rows per cell, reddish-brown in colour.
DistributionTop of page
N. officinale has been introduced to east and southeast Asia, sub-Saharan Africa, the Americas and the Caribbean, Australia, New Zealand and some Pacific islands (USDA-NRCS, 2013; Weeds of Australia, 2013; PIER, 2014; USDA-ARS, 2014; USDA-NRCS, 2014). Howard and Lyon (1952b) suggested that N. officinale, since it is commonly cultivated, is more likely to be introduced than either N. microphyllum or the hybrid between the two species, N. x sterile.
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
History of Introduction and SpreadTop of page
Although watercress has been gathered from the wild as a fresh vegetable since ancient times, commercial cultivation did not start until the 19th century. The first commercial cultivation of N. officinale was recorded in England, UK, in 1808, and the crop was grown extensively in the clean, free-flowing streams of southern England during the 1800s.
Due to the similarity of N. officinale to N. microphyllum, knowing when the former species was introduced to the USA is extremely difficult (IPANE, 2014). The earliest reported incidence of the plant in the country came from southern New England near Yale University, New Haven, Connecticut, in 1831 (IPANE, 2014). However, it may have arrived as early as the mid-1700s.
N. officinale was described in 1857 as a rare escape from cultivation in the USA, but by the end of the 1800s it had reached the west coast (IPANE, 2014). By 1900, it had been reported from 17 US states, including the New England states of Connecticut, Massachusetts and Vermont (IPANE, 2014).
IPANE (2014) reported that in 1899 near Concord, Massachusetts, Rorripa nasturtium-aquaticum [N. officinale] ‘was so abundant that it was removed in cartloads to prevent the stream from flooding the nearby area.’
In Australia, N. officinale seems to have been first collected in Tasmania in 1869 (Australia’s Virtual Herbarium, 2014), but whether the plants were being cultivated or not was not recorded.
Healy (1962, in Healy, 1996) reported that watercress was introduced to New Zealand by the French at Akaroa, South Island, in 1840 to provide food for crews and passengers of French ships calling at the port. By 1857 it had become a nuisance, impeding boats on the Avon River, and a reward was offered for its eradication (Healy, 1969). Nevertheless, it spread rapidly (deliberately or accidentally) and Thomson (1922) reported that a few years after its introduction to Canterbury ‘it blocked the Avon and other streams in the vicinity of Christchurch.’ There were reports of watercress growing ‘to gigantic proportions, being as much as 14 feet [4.3 metres] in length, and stout in proportion,’ (Thomson, 1922), and of ‘a size never seen in Europe’ (Hooker, 1864). However, in 1922 Thomson (1922) reported plant size to be ‘quite normal.’
Risk of IntroductionTop of page
N. officinale has become naturalised in many countries outside its native range, and is widely grown as a crop. It may become even more widely spread in future, most likely to be the result of its deliberate introduction as a food plant. Accidental introduction could result from contaminated aquarium stock, although this would be unlikely to legally pass modern biosecurity border checks.
HabitatTop of page
N. officinale is a rapid coloniser of streams and small waterways, boggy or marshy ground. Mason (1982) commented that, in New Zealand, N. microphyllum is common in slow streams and shallow waters, but sometimes grows completely submerged in faster waters, although it does not flower in that situation.
Howard and Lyon (1952b) suggested that N. officinale species may be less tolerant of dry conditions and of frost than N. microphyllum, and also that it may make it less resistant to grazing by livestock. Its lower tolerance of cold conditions perhaps explains its lower altitudinal limits compared to N. microphyllum (Howard and Lyon, 1952b). This difference in the temperature tolerance of the two species is reinforced by their distribution in New Zealand, where N. microphyllum is more common further south (Mason, 1982; Coffey and Clayton, 1988).
Habitat ListTop of page
Biology and EcologyTop of page
As a long day plant, N. officinale flowers as day length increases, and flowering tends to occur in mid to late summer (Bleasdale, 1964). Flowers are self- or cross-pollinated. Insects are the main pollination agents (Johnson, 1974). Seed pods shatter open and scatter seed when they are ripe, with most seeds falling close to the parent plant. A proportion of the seeds can float for 12 hours or even longer (Howard and Lyon, 1952). Seed production is high, at about 29 seeds per fruit and 20 or more fruits per inflorescence (Howard and Lyon, 1952b).
Seeds germinate soon after being shed, giving 92-100% germination within a week on moist filter paper in the light. Seed is viable for up to about 5 years when stored dry in packets in the laboratory, but apparently loses viability with longer storage (Howard and Lyon, 1952b). The same authors obtained no germination in darkness, but found that a very short exposure to light (5 minutes) after the seeds have absorbed water will lead to some germination (Howard and Lyon, 1951).
Howard and Lyon (1952b) suggested that reproduction by seedlings is probably effective if seeds fall on bare ground, but that once the ground is covered by vegetation, vegetative reproduction becomes more important.
N. officinale is perennial and, since it can reproduce asexually from vegetative stems, it can probably live for several years (Howard and Lyon, 1952b).
The growth of N. officinale in natural streams has been studied in Britain (Castellano, 1977, cited in Howard-Williams et al., 1982), North America (Kaskey and Tindall, 1979) and New Zealand (Howard-Williams et al., 1982). N. officinale is very fast-growing, with the most rapid growth occurring in spring to mid-summer. Leaf and root tissue increases early in the growing season, but in late summer to winter plants have over 60% of their dry matter in the stems. Howard-Williams et al. (1982) estimated that during peak growing times, the biomass of a New Zealand N. officinale population doubled in 12.2 days. The same authors measured no growth in May (late autumn). Growth can be frosted in winter (Howard and Lyon, 1952b).
N. officinale has leaves that remain green in autumn, but the plant may be susceptible to frost damage in winter and spring (Vaughan and Geissler, 1997). Watercress develops two types of roots: basal anchorage roots that secure the plant and adventitious roots that float in the water. Both types take up nutrients, although Cumbus and Robinson (1977) established that a greater proportion of phosphate and potassium was absorbed by adventitious roots of N. officinale than basal roots.
Shaw (1949, cited in Howard and Lyon, 1952a) suggested that N. officinale usually occurs on calcareous soils. Howard and Lyon (1952a) added that N. officinale may have higher calcium and pH requirements than N. microphyllum. Smith (2007) cited Seelig (1974) when writing that N. officinale is not considered to have a high nutrient demand. However, it does absorb nitrogen and phosphorus and has been considered for use in stripping nutrients from streams (Howard-Williams et al., 1982).
N. officinale occurs at the edges of rivers, streams, ditches and springs, but not in stagnant water (Howard and Lyon, 1952b). It grows on gravel, sand, silt or clay but not on acid or alkaline peats. It prefers to grow in slow-flowing, clean water 5-10 cm deep with an optimum pH of 7.2, favouring streams fed from springs originating from chalk or limestone substrata.
Going et al. (2008) investigated the effects of shading on N. officinale and found that total biomass and root biomass decreased with decreasing light levels, and that the species displayed considerable morphological plasticity, acclimatising to low light conditions primarily by increasing leaf area and canopy surface area.
Notes on Natural EnemiesTop of page
Howard and Lyon (1952a) listed many insects and other animals that sometimes damage N. officinale, including water snails, shrimps, springtails, thrips, aphids, caddis-fly larvae, butterflies, beetles, weevils, flies, wildfowl, deer and muskrat. Thompson (1922) reported N. officinale to be commonly infested by Aphis brassicae in New Zealand.
Major pests of cultivated watercress crops include various species of aphids, including the green peach aphid (Myzus persicae). Another pest of economic importance is the diamondback moth (Plutella xylostella) which feeds exclusively on cruciferous host plants. The caterpillar stage of this moth can cause considerable feeding damage on the leaves and young growing shoots. Stink bugs (Nezara viridula, Nysius spp.) are another occasional pest which can cause wilting of shoots. Cyclamen mite (Stenotarsonemus pallidus [Phytonemus pallidus]) is a common pest in certain production regions. Slugs and snails are also pests, mostly of outdoor production beds, often found where there is high rainfall and excessive water on the plants. Freshwater pulmonate species (Lymnaea ovata, L. stagnalis, Physa acuta, Planorbis leucostoma) are also known to inhabit watercress beds in France. These species may be infected with Fasciola hepatica, which causes fascioliasis in humans who consume the watercress (Dreyfuss, 2003; WHO, 2007).
Diseases of watercress include Cercospora leaf spot (Cercospora nasturtii), which largely affects older leaves in areas of high humidity, and Septoria leaf spot (Septoria sisymbrii) (Andrianova and Minter, 2004). Black rot (Xanthomonas campestris) is common in outdoor crops under prolonged rainy periods and high humidity. Pythium ultimum, or 'damping off' disease, is a common problem in watercress production, particularly in young or weakened plants. Crook-root is a disease caused by a water-borne fungus (Spongospora subterranean f. sp. nasturtii) which causes the root to swell, distort and become brittle. Watercress yellows is a serious disease of watercress grown in Hawaii that causes reduced leaf size, leaf yellowing and crinkling, and witches' brooms. Watercress yellows is caused by a phytoplasma first detected in 2001 (Borth et al., 2006).
Algae can be a problem in many watercress systems, including hydroponic systems, and can block the flow of water, causing stagnation and overheating of bed systems.
In New Zealand, natural watercress beds growing at the edges of waterways are often invaded by species like Apium nodiflorum and Mimulus guttatus, which tend to limit the area occupied by N. officinale (P. Champion, pers. comm., 2014).
Means of Movement and DispersalTop of page
Natural dispersal (non-biotic)
N. officinale seeds and stem fragments are commonly spread by water, especially during floods (Weeds of Australia, 2014).
Vector transmission (biotic)
N. officinale seeds and stem fragments can become attached to the feet of animals, including birds, which could then transport these propagules both locally and, possibly, for long distances. Seeds and fragments may be dispersed in mud attached to animals (Weeds of Australia, 2014).
Accidental contamination of aquarium plants or animals could spread the species.
N. officinale is commonly cultivated for human consumption as a vegetable and for medicinal purposes, and could become even more widely dispersed by human agency. Although it can certainly be considered invasive, its benefits are usually thought to outweigh possible costs of its invasiveness.
Economic ImpactTop of page
N. officinale is one of the worst weeds in cultivated beds of brown cress (N. x sterile ) in the UK, since it grows taller and faster than brown cress and tends to crowd it out (Howard and Lyon, 1952b).
When first introduced to areas outside its native range, watercress reportedly often becomes rampant, and expensive measures have been taken to control it. In 1899 near Concord, Massachusetts, USA, watercress was so abundant that it was removed in cartloads to prevent the stream from flooding the nearby area (IPANE, 2014). Similarly in New Zealand, following its introduction in 1840, ‘by 1864 its control/eradication in the Avon River was costing more than £300 per annum, a large sum and financial burden’ (Healy 1996). Since N. microphyllum, N. officinale and N. x sterile were not described separately until the 1940s (Howard and Lyon, 1952a), it is impossible to know which of the present-day species was responsible for these problems. However, their effects are nowhere near so severe in modern times, and in many places watercress has been partly displaced by other species of aquatic plants.
Environmental ImpactTop of page
Impact on habitats
In Connecticut, USA, N. officinale is listed as an invasive and potentially invasive aquatic plant (Bugbee and Balfour, 2010). The plant is classed as Category 2: declared invader in South Africa (Henderson and Cilliers, 2002).
When N. officinale was newly invasive it reportedly had dramatic impacts on existing habitats and their native flora and fauna, reputedly blocking waterways in parts of the USA and of New Zealand, altering habitat structure and composition (Healy, 1968; IPANE, 2014). Over time, however, it seems to have become less aggressive and is now considered just one of a number of alien aquatic weeds in waterways.
Social ImpactTop of page
The species is an important food source in many of the countries where it is native or to which it has been introduced. Although introduced well after the Maori settlement of New Zealand, it has become a popular food of the Maori, who know it as kowhitiwhiti.
One of the downsides of consumption of wild-growing watercress is that it often carries the common liver fluke (Fasciola hepatica) if growing in places near where livestock graze. The alternate hosts of the fluke are water snails, which often live on watercress and can therefore pass the infection on to humans, where it can cause fasciolosis. The disease is rare in some countries, but more prevalent in others. It is a major health problem in Bolivia, Ecuador and Peru, the Nile Delta in Egypt, and central Vietnam (WHO, 2007). Cooking watercress kills the parasite.
Various studies have found cress contaminated with a high number of protozoan pathogens (Soares and Cantos, 2006), significant levels of E. coli and the occurrence of Campylobacter (Edmonds and Hawke, 2004), and heavy metal contamination (Kara, 2005; CPC, 2012).
UsesTop of page
N. officinale is commonly grown as a crop for human consumption in salads or as a vegetable. In South Africa, controlled cultivation is permitted, despite the plant being classed as a Category 2: declared invader (Henderson and Cilliers, 2002). Watercress sprouts are commercially produced and harvested within a few days of germination.
Wild-growing plants of the species is often used by people as a cheap and natural source of green salads or vegetables. Mature watercress contains small amounts of sugars and fats, folic acid, a range of B vitamins and minerals, also vitamin E. The amounts of protein (3%), iron (2 mg/100 g), carotenes (a high content of beta carotene) and vitamin C (62 mg/100 g) are relatively high (Vaughan and Geissler, 1997). The peppery pungency of the stems and foliage is derived from glucosinolate compounds.
Duke (2014) provided a list of ethnobotanical uses for N. officinale, including as an abortifacient and for treating colds, coughs and eczema. Traditionally, watercress has long been used to treat a number of ailments, with claims that it can improve blood circulation (Matsushima et al., 2006) for the treatment of renal colic, liver diseases (Guarrera et al., 2005) as a mild stimulate, a diuretic, an expectorant and a digestive aid. The popularity of watercress as a 'health food' is growing, largely due to recent studies and reports of the anti-cancer compounds it contains.
Uses ListTop of page
Human food and beverage
Detection and InspectionTop of page
In New Zealand, Coffey and Clayton (1988) suggested that N. officinale is more common than N. microphyllum in the North Island of New Zealand and the reverse is true in the South Island, which may relate to the observation by Howard and Lyon (1952a) that N. officinale is ‘considerably less frost-resistant’ than N. microphyllum.
Similarities to Other Species/ConditionsTop of page
N. officinale and N. microphyllum are very similar and grow together. They are best distinguished by the surfaces of their seeds, and whether the siliques (seed pods) have one or two rows of seeds. In N. officinale, the seeds are in 2 rows and are coarsely reticulate, with 20-50 polygonal depressions per face. By contrast, in N. microphyllum the seeds are more or less in one row, and reticulate with 100-150 polygonal depressions per face. N. officinale also tends to have smaller flowers, shorter pedicels, and broader siliques than N. microphyllum (Webb et al., 1988).
The hybrid between N. officinale and N. microphyllum, N. x sterile, has been recorded from Britain (Howard and Lyon, 1952b) and New Zealand (Webb et al., 1988). It is intermediate between the parents and only produces seeds when N. microphyllum is the female parent (Howard and Lyon, 1952b). N. x sterile can be recognized by its short fruits, which contain only an occasional seed. It has only about 20% good pollen and the good pollen is very variable in size. Howard and Lyon (1952a) stated that it resembled N. microphyllum more than N. officinale. It is commonly cultivated as brown or winter cress (Howard and Lyon, 1952a).
Bleeker et al. (1999) provided excellent photographs of the fruit shape and structure of the seed coat of both species and the hybrid between them.
Weeds of Australia (2014) suggested that N. officinale is similar to yellow marsh-cress (Rorippa palustris) and creeping yellow cress (Rorippa sylvestris). R. palustris is an annual or biennial upright plant with pale yellow flowers and a small fruit (5-9 mm long) with two rows of seeds on either side of a central division. Rorippa sylvestris is a creeping or semi-upright plant with bright or light yellow flowers, again with small fruit (4-15 mm long) with two rows of seeds on either side of a central division.
Prevention and ControlTop of page
Biological control would probably not be tolerated in most countries, since many people collect and consume wild-growing watercress (of any species).
An attempt at weed control and eradication in New Zealand in 1856, using the Australian black swan (Cygnus atratus), was unsuccessful, although the Australian black swan thrived and became a problem in its own right (Healy, 1996).
Thomson (1922) mentioned that planting willows along the banks of streams reduces the incidence of N. officinale, probably more the result of shading than of nutrient depletion. However, willows themselves can become serious weeds in their turn.
Chemical control is rarely warranted for the species.
Control by utilization
According to Howard and Lyon (1952a; b) the species is often extensively grazed by cattle, especially in dry weather.
ReferencesTop of page
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