Nasturtium microphyllum (one-row watercress)
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Habitat List
- Biology and Ecology
- Notes on Natural Enemies
- Means of Movement and Dispersal
- Impact Summary
- Social Impact
- Risk and Impact Factors
- Similarities to Other Species/Conditions
- Prevention and Control
- Links to Websites
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Nasturtium microphyllum Boenn. ex Rchb.
Preferred Common Name
- one-row watercress
Other Scientific Names
- Nasturtium officinale var. microphyllum (Boenn. ex Rchb.) Thell.
- Nasturtium officinale var. olgae N. Busch
- Nasturtium uniseriatum Howard & Manton
- Pirea olgae T. Durand ex Prantl
- Rorippa microphylla (Boenn. ex Rchb.) Hyl. ex Á. Löve & D. Löve
- Rorippa nasturtium-aquaticum var. longisiliqua (Irmisch) B. Boivin
International Common Names
- English: onerow watercress; one-rowed watercress; watercress
Local Common Names
- : cresson à petites feuilles
- : narrow-fruited watercress
- Germany: kleinblättrige Brunnenkresse
- Japan: chisa; kawara-chisa
- Netherlands: Slanke waterkers
- USA/Hawaii: leko
Summary of InvasivenessTop of page
N. microphyllum is a species of watercress, a perennial aquatic or semi-aquatic herb native to the Middle East, parts of North Africa and Europe. It has been introduced to Japan, Yemen, Sub-Saharan Africa, the Americas, Australia and New Zealand. N. microphyllum has been introduced to many countries well outside of its native range, including many parts of the USA and Australasia. Like N. officinale, this species has spread in some of the countries it has been introduced to, invading waterways and swamping existing native vegetation. Staples et al. (2000) listed it as an ‘invasive or potentially invasive cultivated plants in Hawaii.' N. microphyllum is sometimes not considered as a potential invasive as it is not often a problem, even though related Nasturtium species can be problematic (Thomson, 1922; IPANE, 2013).
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Plantae
- Phylum: Spermatophyta
- Subphylum: Angiospermae
- Class: Dicotyledonae
- Order: Capparidales
- Family: Brassicaceae
- Genus: Nasturtium
- Species: Nasturtium microphyllum
Notes on Taxonomy and NomenclatureTop of page
The three types of watercress (N. microphyllum, N. officinale and the commonly cultivated hybrid between them, N. x sterile) were not usually recognized before about 1946 (Howard and Lyon, 1952a). The confusion between N. microphyllum, N. officinale and N. x sterile has meant that determining the presence of N. microphyllum has proved difficult. Howard and Lyon (1952a) suggested that, at the time they wrote, ‘most of the records for countries outside Europe’ probably referred to N. officinale and not to N. microphyllum. Bleeker et al. (1999) noted that ‘N. x sterile is widely distributed in Central Europe, but has been notoriously overlooked and misidentified as N. microphyllum in the past’, and added that the hybrid is the most common Nasturtium taxon in northern Germany.
DescriptionTop of page
Perennial aquatic or semi-aquatic herb, prostrate with creeping or floating hairless stems up to 1 m long. The stems are hollow, angular mostly creeping, from taproot and fibrous roots, often rooting at the nodes, then ascending or floating. Leaves alternate, dark green to bronze, hairless, all similar but becoming smaller near the inflorescence, pinnate, with 3-7 leaflets, ovate to oblong; margins entire or sinuate; terminal leaflet usually larger than the lateral leaflets. Inflorescence of compact terminal racemes that rapidly elongate in fruit. Flower stalks hairless, slender, spreading to deflexed at fruiting, (8)-12-20-(30) mm long. Sepals 2.5-3.5 × 1 mm. Petals white, (4)-5-6 × 1.5-2.5 mm. Silique glabrous, narrow-oblong to linear, curved, (10)-15-25-(30) × c. 1.5 mm; valves with distinct midrib at least below; style c. 1 mm long. Seeds in more or less one row per cell, brown, about 1 mm long, reticulate with 100-150 polygonal depressions per face. The flowers are hermaphrodite and insect pollinated.
DistributionTop of page
N. microphyllum is native to the Middle East, parts of North Africa and Europe. It has been introduced to Japan, Yemen, Sub-Saharan Africa, the Americas, Australia and New Zealand. It should be noted that reports of the introduction, naturalisation and rapid spread of watercress in Australia (Australia’s Virtual Herbarium, 2013) and New Zealand (Thomson, 1922) are difficult to ascribe to a particular species.
The confusion between N. microphyllum, N. officinale and N. x sterile has meant that determining the presence of N. microphyllum has proved difficult. Howard and Lyon (1952a) suggested that, at the time they wrote, ‘most of the records for countries outside Europe’ probably referred to N. officinale and not to N. microphyllum. Bleeker et al. (1999) noted that ‘N. x sterile is widely distributed in Central Europe, but has been notoriously overlooked and misidentified as N. microphyllum in the past’, and added that the hybrid is the most common Nasturtium taxon in northern Germany.
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.
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|-Himachal Pradesh||Present||Native||USDA-ARS, 2013|
|-Jammu and Kashmir||Present||Native||USDA-ARS, 2013|
|Iran||Present||Native||USDA-ARS, 2013||North of Iran (Naqinezhad, 2006)|
|Pakistan||Present||Native||USDA-ARS, 2013||Northwest Frontier Province only (Flora of Pakistan, 2013)|
|Congo Democratic Republic||Present||Introduced||USDA-ARS, 2013|
|South Africa||Present||Introduced||Shaw, 1947|
|Canada||Present||Present based on regional distribution.|
|-British Columbia||Present||Introduced||USDA-NRCS, 2013|
|-New Brunswick||Present||Introduced||USDA-NRCS, 2013|
|-Newfoundland and Labrador||Present||Introduced||USDA-NRCS, 2013|
|-Prince Edward Island||Present||Introduced||USDA-NRCS, 2013|
|Saint Pierre and Miquelon||Present||Introduced||USDA-NRCS, 2013|
|USA||Present||Present based on regional distribution.|
|-New Hampshire||Present||Introduced||USDA-NRCS, 2013|
|-New Mexico||Present||Introduced||USDA-NRCS, 2013|
|-New York||Present||Introduced||USDA-NRCS, 2013|
|-North Carolina||Present||Introduced||USDA-NRCS, 2013|
|Argentina||Present||Introduced||USDA-NRCS, 2013||Entre Rios|
|Czech Republic||Present||Native||USDA-ARS, 2013|
|-New South Wales||Present||Introduced||Weeds of Australia, 2013||Some parts of eastern NSW|
|-Queensland||Present, few occurrences||Introduced||USDA-NRCS, 2013||South eastern parts|
|-South Australia||Present||Introduced||USDA-NRCS, 2013||South eastern parts|
|-Tasmania||Present, few occurrences||Introduced||USDA-ARS, 2013||South eastern parts|
|-Victoria||Present||Introduced||USDA-ARS, 2013||Southern and eastern parts|
|New Zealand||Present||Introduced||USDA-ARS, 2013|
History of Introduction and SpreadTop of page
Owing to the similarity between N. microphyllum and N. officinale, knowing when it was introduced into the USA is extremely difficult (IPANE, 2013). The earliest record of the plant came from Waltham, Massachusetts, in 1861. It is likely that it became established in the USA in the mid-1800s, as records and specimens began to be collected at that time.
Similarly, reports of the introduction, naturalisation and rapid spread of watercress in Australia (Australia’s Virtual Herbarium, 2013) and New Zealand (Thomson, 1922) are difficult to ascribe to a particular species. In Australia it seems to have been first collected in Tasmania in 1869 (Australia’s Virtual Herbarium, 2013). Healy (1962) claimed that the French introduced watercress to Akaroa, New Zealand, in 1840, but this could have referred to one or more species.
IntroductionsTop of page
Risk of IntroductionTop of page
Howard and Lyon (1952b) suggested that, since N. microphyllum is not usually cultivated, it is less likely to be introduced than either N. officinale or the hybrid between the two species, N. x sterile, both of which are grown as food and herbal plants and which have been introduced to many countries (Howard and Lyon, 1952a). However, since the watercress species often grow together, N. microphyllum may sometimes have been introduced by accident.
Accidental introduction could also result from contaminated aquarium stock, although this would be unlikely to legally pass modern biosecurity border checks.
HabitatTop of page
N. microphyllum occurs at the edges of rivers, streams, ditches and springs, but not in stagnant water. It grows on gravel, sand, silt or clay but not on either acid or alkaline peats.
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 (Mason, 1982). In the UK, N. microphyllum occurs in similar habitats to those described for N. officinale and this seems to be true elsewhere (Howard and Lyon, 1952a). However, N. microphyllum may be more tolerant of dry conditions and of frost than N. officinale, which might explain its higher altitudinal limits (Howard and Lyon, 1952b).
In Hawaii it is 'naturalized in running water or seasonally wet areas' (Wagner et al., 1999).
Habitat ListTop of page
|Terrestrial ‑ Natural / Semi-natural||Riverbanks||Present, no further details|
|Irrigation channels||Principal habitat||Natural|
|Rivers / streams||Principal habitat||Natural|
Biology and EcologyTop of page
The chromosome number is reported as 2n = 64 (Howard and Lyon, 1952b). The hybrid between N. microphyllum and N. officinale, known as N. x sterile, is common and is cultivated as ‘brown’ or ‘winter cress’ (Howard and Lyon, 1952a). It has a chromosome number of 2n = 48 and at meiosis behaves as a typical allotriploid, forming 16 bivalents and 16 univalents (Howard and Manton, 1946).
N. microphyllum flowers are hermaphrodite. Being a long day plant, watercress flowers in response to increasing day length in spring and summer (Bleasdale, 1964). N. microphyllum is self or cross pollinated, mostly by insects (Howard and Lyon, 1952b; Johnson, 1974). Seed pods shatter open and scatter seed when ripe. Seed production is very high at about 29 seeds per fruit and 20 or more fruits per inflorescence. Most seeds fall close to the parent plant (Howard and Lyon, 1952b). Seeds can germinate soon after being shed, with 92-100% germination within a week on moist filter paper in the light. Seed is viable 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). Seedlings are very similar to those of N. officinale but grow more slowly and have a more slender hypocotyl (Howard and Lyon, 1952b). In the later stages they have a more prostrate growth form. 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 plants vegetative reproduction becomes more important.
Physiology and phenology
N. microphyllum flowers in June, about 14 days later than N. officinale (Howard and Lyon, 1952b). Growth can be frosted in winter, but N. microphyllum is apparently more frost-tolerant than N. officinale (Howard and Lyon, 1952b).
Michaelis (1976) observed seasonal changes in growth of N. microphyllum over two seasons in Waikoropupu Springs in New Zealand. Number of leaflets per leaf was uniform for the youngest ten leaves on any given shoot, increasing from 3-7 leaflets in autumn and winter (early April to early August) to a spring and summer modal value of 9 or 11 (mid-October to mid-February). Shoots of N. microphyllum emerged from shallow water between October and May (late spring to autumn) and flowers were first observed in late November or early December, and flowering continued until May. Pods were present from early January to late May. N. microphyllum plants growing at depths greater than 1 m showed little seasonal change in growth form, did not flower, and maintained 1-5 leaflets per leaf all year round. Michaelis (1976) also measured the biomass of N. microphyllum in Waikoropupu Springs and found this reached about 1500 g m-2 between February and May (late summer and early autumn), and then declined. Up to about 30% of the biomass was consumed by cattle at some times.
Michaelis (1976) examined the occurrence of N. microphyllum in cold water springs in New Zealand. She found some emergent plants were rooted in gravel overlain by silt, but others floated to form a bed extending out for 2-12 m from the edge of the springs. Several patches of submerged N. microphyllum were rooted in gravel at depths ranging down to 6.5 m (the water there is especially clear). The growth form of these submerged plants depended on the depth at which the plant was growing. Generally, submerged plants were smaller and had a simpler growth form than emergent plants. Those at a depth of 3 m had much thinner leaflets, whilst those 6.5 m deep were a translucent dark green and so thin that they were always rolled up. Number of leaflets per leaf, leaf length, internode distance, maximum and mean stem length all became less with increased depth at which the plants were growing.
N. microphyllum is perennial and, since it can reproduce asexually from vegetative stems, can probably live for several years (Howard and Lyon, 1952b).
Howard and Lyon (1952a; b) listed a number of species commonly associated with N. microphyllum, or in some cases the hybrid N. x sterile, in different environments in Britain.
Environmental requirements for optimal growth of N. microphyllum are not well-known, but are presumed to be similar to N. officianle (Howard and Lyon, 1952b). It grows well in warm temperate climates. N. microphyllum seems to be less demanding of calcium than is N. officinale. Shaw (1949, cited in Howard and Lyon, 1952a) suggested that N. microphyllum is usually found in non-calcareous areas (based on information from Gloucestershire, UK), unlike N. officinale, which usually occurs on calcareous soils. Howard and Lyon (1952a) also suggested that N. microphyllum may have a lower calcium and pH requirement than N. officinale. In New Zealand, Michaelis (1976) found N. microphyllum growing in Waikoropupu Springs, where water temperature is a constant 11.7oC and the calcium content is high, at 63 g m-3.
ClimateTop of page
|Cf - Warm temperate climate, wet all year||Preferred||Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year|
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, collembola, thrips, aphids, caddis-fly larvae, butterflies, beetles, weevils, flies, wildfowl, deer and muskrats. Howard and Lyon (1952b) indicated that the same pests probably attack N. microphyllum.
In New Zealand’s Waikoropupu Springs, Michaelis (1976) found that submerged N. microphyllum was free from pests and diseases, but that emergent plants carried a diverse invertebrate fauna with a high biomass. The number of species and biomass decreased with an increase in the depth at which the watercress grew. Natural watercress beds growing at the edges of waterways in New Zealand are often invaded by species like Apium nodiflorum and Mimulus guttatus, which tend to limit the area occupied by N. officinale or N. microphyllum (P. Champion, pers. comm.).
Means of Movement and DispersalTop of page
Natural dispersal (non-biotic)
As with N. officinale, seeds and stem segments are commonly spread by water, especially during floods (Weeds of Australia, 2013). Parts of floating beds of N. microphyllum are sometimes washed downstream once or twice a year following grazing by cattle or human interference (Michaelis, 1976).
Vector transmission (biotic)
Seeds and stem fragments may be dispersed in mud attached to animals and vehicles (Weeds of Australia, 2013). Seeds and fragments can become attached to the feet of birds could be transported both locally and, possibly, for longer distances.
Accidental contamination of aquarium plants or animals could possibly spread the species.
Unlike N. officinale, N. microphyllum is not usually cultivated, although naturally growing plants may be consumed for vegetable or medicinal purposes in some countries, and could be deliberately introduced to other countries as useful plants.
Impact SummaryTop of page
|Environment (generally)||Positive and negative|
ImpactTop of page
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 species were responsible for historic infestations. However, the effects of invasive watercress are reduced in modern times, as in many places watercress has been partly displaced by other species of aquatic plants.
Social ImpactTop of page
N. microphyllum is an important food source in many of the countries where it is native or where it was introduced. Although introduced well after Maori settlement of New Zealand, it has become a favoured food of Maori, who know it as kowhitiwhiti.
One of the downsides of consumption of wild-growing watercress is that it commonly carries the common liver fluke (Fasciola hepatica) when 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 watercress contaminated with a high number of protozoan pathogens (Soares and Cantos, 2006), significant levels of E. coli and Campylobacter (Edmonds and Hawke, 2004), and heavy metal contamination (Kara, 2005).
Risk and Impact FactorsTop of page Invasiveness
- Proved invasive outside its native range
- Has a broad native range
- Long lived
- Fast growing
- Has high reproductive potential
- Reproduces asexually
- Modification of natural benthic communities
- Modification of nutrient regime
- Reduced amenity values
UsesTop of page
N. microphyllum, although not grown as a crop like N. officinale, is not easily distinguishable from the other species and is no doubt regularly harvested from ponds and streams for human consumption.
N. microphyllum is often used by people as a cheap and natural source of green salads or vegetables. Imtiaz et al. (2012) found that extracts of N. microphyllum in Pakistan showed good antibacterial activity against strains of bacteria commonly found in the environment and of fungi that cause infections. The same authors quoted Hall et al. (2002) in claiming N. microphyllum ‘can be used to treat lung cancer and chest problems.’
Similarities to Other Species/ConditionsTop of page
N. microphyllum is easily confused with N. officinale. N. microphyllum and N. officinale are very similar and are most reliably distinguished by the surfaces of their seeds and the siliques (seed pods). 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 in more or less one row per locule, and reticulate with 100-150 polygonal depressions per face. N. microphyllum also tends to have larger flowers, longer pedicels, and narrower siliques than N. officinale (Webb et al., 1988). Bleeker et al. (1999) produced excellent photographs of the fruit shape and structure of the seed coat of the two species and of the hybrid (N. x sterile). N. microphyllum is a less variable species than N. officinale (Shaw, 1949), more prostrate than N. officinale, and in cold weather develops considerably more anthocyanin pigmentation, giving the leaves a purple-brown colour (Howard and Lyon, 1952b). Seedlings of N. microphyllum are very similar to those of N. officinale but grow more slowly and have a more slender hypocotyl (Howard and Lyon, 1952b). In the later stages they have a more prostrate growth form.
The hybrid N. x sterile has been recorded from Britain (Howard and Lyon, 1952b) and New Zealand (Webb et al., 1988). It is intermediate between the parent species. N. x sterile can be recognized by its short fruits which contain only an occasional seed. It has only about 20% of good pollen and the good pollen is very variable in size (although Bleeker et al. (1997) claimed that it showed considerable seed set and pollen quality). It resembles N. microphyllum more than N. officinale (Howard and Lyon, 1952a).
N. microphyllum, N. officinale and N. x sterile often grow together or in close proximity (Howard and Lyon, 1952b). However, in New Zealand, Coffey and Clayton (1988) suggested that N. officinale is more common than N. microphyllum in the North Island and vice versa 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.
Prevention and ControlTop of page
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.
Biological control would not be tolerated in most countries, since many people collect and consume wild-growing watercress.
Chemical control is rarely warranted for watercress, although glyphosphate has been suggested (Monsanto, 2013).
Control by utilization
According to Howard and Lyon (1952a; b) N. microphyllum is often extensively grazed by cattle, especially in dry weather. However, its more prostrate growth may make it more resistant to grazing by livestock than N. officinale (Howard and Lyon, 1952b).
ReferencesTop of page
Amos J-A, 2007. Watercress has its benefits: watercress nutrition examined. Lifescript: Healthy Living for Women. http://www.lifescript.com/food/articles/w/watercress_has_its_benefits.aspx#disqus_thread
Australian Weeds Committtee, 2013. Weeds of Australia. Canberra, Australia: Australian Weeds Committtee. http://www.weeds.org.au/
Barkworth H, 1938. Taints and off-flavours of milk. Part I. Dairy Industry, 3:367-70
Bleeker W, 1996. Diploma thesis. Osnabrück: Department of Biology/Chemistry, University of Osnabrück
Bleeker W, Hurka H, Koch M, 1997. Occurrence and morphology of N. sterile (Airy Shaw) Oef. in Sudwestniedersachsen and adjacent areas. (Zum Vorkommen und zur Morphologie von N. sterile (Airy Shaw) Oef. in Sudwestniedersachsen und angrenzenden Gebieten.) Floristische Rundbriefe, 31(1):1-8
Bushra Imtiaz, Fozia, Abdul Waheed, Ali Rehman, Hussain Ullah, Hamid Iqbal, Abdul Wahab, Mamoona Almas, Ijaz Ahmad, 2012. Antimicrobial activity of Malva neglecta and Nasturtium microphyllum. International Journal of Research in Ayurveda and Pharmacy (IJRAP), 3(6):808-810. http://www.ijrap.net/admin/php/uploads/907_pdf.pdf
Castellano E, 1977. Productivity of Rorippa nasturtium-aquaticum (L.) Hayek (Productividad de Rorippa nasturtium-aquaticum (L.) Hayek). Merida, Venezuela: Universidad de los Andes
Duke JA, 2013. Nasturtium officinale (Brassicaceae). Dr. Duke's Phytochemical and Ethnobotanical Databases: Ethnobotanical uses. http://www.ars-grin.gov/cgi-bin/duke/ethnobot.pl?ethnobot.taxon=Nasturtium%20officinale
Flora of Pakistan, 2014. Flora of Pakistan/Pakistan Plant Database (PPD). Tropicos website St. Louis, Missouri and Cambridge, Massachusetts, USA: Missouri Botanical Garden and Harvard University Herbaria. http://www.tropicos.org/Project/Pakistan
Healy AJ, 1962. Involuntary changes in the Vegetation of Canterbury. Unpublished lecture, 15 August 1962. Canterbury Branch, New Zealand: Royal Society of New Zealand
Healy AJ, 1969. The adventive flora in Canterbury. In: The Natural History of Canterbury [ed. by Knox, G. A.]. Wellington, New Zealand: A.H. & A.W. Reed, p. 279
Healy AJ, 1996. Some consequences of the introduction of watercress by the French at Akaroa. In: Expansion of comments made during discussion at the Etienne Raoul Symposium, 23 November 1996. http://bts.nzpcn.org.nz/bts_pdf/Cant_1998_32__9-10.pdf
Howard HW, Lyon AG, 1952. Nasturtium microphyllum Boenningh. Ex Rchb. (Nasturtium uniseriatum Howard & Manton; Rorippa microphylla (Boenn.) Hyl. Biological flora of the British Isles. Journal of Ecology, 40:239-245
Howard HW, Lyon AG, 1952. Nasturtium officinale R. (Rorippa nasturtium-aquaticum (L.) Hayek). Biological flora of the British Isles. Journal of Ecology, 40:228-238
Howard-Williams C, Davies J, Pickmere S, 1981. The dynamics of growth [of], the effects of changing area [on] and nitrate uptake by watercress Nasturtium officinale R. Br. in a New Zealand stream. Journal of Applied Ecology, 19(2):589-601
Johnson AG, 1974. Possibilities and problems in breeding of watercress. In: Symposium on Research on the Watercress Crop, Bath University. Bath, UK: Bath University
Kara Y, 2005. Bioaccumulation of Cu, Zn and Ni from the wastewater by treated Nasturtium officinale. International Journal of Environmental Science and Technology, 2(1):63-67. http://www.ceers.org/ijest/issues/abstract_result.asp?ID=201009
Mason R, 1982. Aquatic Weeds. In: Identification of weeds and clovers [ed. by Healy, A. J.]. Featherston, New Zealand: Editorial Services Limited, 230-264
Michaelis FB, 1976. Watercress (Nasturtium microphyllum Boenn. Rchb.) and N. officinale in New Zealand cold springs. Aquatic Botany, 2:317-325
Monsanto Ltd, 2013. Roundup: aquatic weed control. http://www.monsanto-ag.co.uk/content.output/180/180/Roundup/Aquatic%20use/Aquatic%20Weed%20Control.mspx
Naqinezhad A, 2006. A short note on the genus Nasturtium R. (Cruciferae) and a new hybrid state from this genus for Iran. Iranian Journal of Botany, 12(1):75-77
Royal Botanic Gardens Sydney, 2013. Australia’s Virtual Herbarium. Sydney, Australia: Royal Botanic Gardens. http://avh.chah.org.au/
Seelig RA, 1974. Fruit and vegetable facts and pointers. Washington, D.C, USA: United Fresh Fruit & Vegetable Association
Smith EN, 2007. Watercress (Nasturtium officinale) production utilizing brook trout (Salvelinus fontinalis) flow-through aquaculture effluent. West Virginia, USA: Davis College of Agriculture, Forestry, and Consumer Sciences at West Virginia University. http://aquaculture.davis.wvu.edu/r/download/121691
Soares B, Cantos GA, 2006. Detection of parasitic structures in vegetables commercialised in the city of Florianopolis, SC, Brazil. Revista Brasieira de Ciencias Farmaceuticas, 42(3):455-460
Staples GW, Herbst D, Imada CT, 2000. Survey of invasive or potentially invasive cultivated plants in Hawaii. Bishop Museum Occasional Papers, 65:35 pp
USDA-ARS, 2013. Germplasm Resources Information Network (GRIN). Online Database. Beltsville, Maryland, USA: National Germplasm Resources Laboratory. https://npgsweb.ars-grin.gov/gringlobal/taxon/taxonomysearch.aspx
USDA-NRCS, 2013. The PLANTS Database. Baton Rouge, USA: National Plant Data Center. http://plants.usda.gov/
Webb CJ, Sykes WR, Garnock-Jones PJ, 1988. Flora of New Zealand Vol IV: Naturalised Pteridophytes, Gymnosperms, Dicotyledons. Christchurch, New Zealand: Botany Division, Department of Scientific and Industrial Research
WHO, 2007. Report of the WHO Informal Meeting on use of triclabendazole in fascioliasis control. http://www.who.int/neglected_diseases/preventive_chemotherapy/WHO_CDS_NTD_PCT_2007.1.pdf
ContributorsTop of page
02/10/13: Original text by:
Ian Popay, consultant, New Zealand, with the support of Landcare Research.
Distribution MapsTop of page
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