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Nasturtium microphyllum
(one-row watercress)

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Datasheet

Nasturtium microphyllum (one-row watercress)

Summary

  • Last modified
  • 27 September 2018
  • Datasheet Type(s)
  • Invasive Species
  • Preferred Scientific Name
  • Nasturtium microphyllum
  • Preferred Common Name
  • one-row watercress
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Plantae
  •     Phylum: Spermatophyta
  •       Subphylum: Angiospermae
  •         Class: Dicotyledonae
  • Summary of Invasiveness
  • 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...

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Pictures

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PictureTitleCaptionCopyright
Nasturtium microphyllum (onerow yellowcress); inflorescence.
TitleInflorescence
CaptionNasturtium microphyllum (onerow yellowcress); inflorescence.
Copyright©Trevor James/Hamilton, New Zealand-2014
Nasturtium microphyllum (onerow yellowcress); inflorescence.
InflorescenceNasturtium microphyllum (onerow yellowcress); inflorescence.©Trevor James/Hamilton, New Zealand-2014
Nasturtium microphyllum (onerow yellowcress); habit in shallow water.
TitleHabit in shallow water
CaptionNasturtium microphyllum (onerow yellowcress); habit in shallow water.
Copyright©Trevor James/Hamilton, New Zealand-2014
Nasturtium microphyllum (onerow yellowcress); habit in shallow water.
Habit in shallow waterNasturtium microphyllum (onerow yellowcress); habit in shallow water.©Trevor James/Hamilton, New Zealand-2014
Nasturtium microphyllum (onerow yellowcress); leaves, showing bronzing.
TitleLeaves, showing bronzing
CaptionNasturtium microphyllum (onerow yellowcress); leaves, showing bronzing.
Copyright©Trevor James/Hamilton, New Zealand-2014
Nasturtium microphyllum (onerow yellowcress); leaves, showing bronzing.
Leaves, showing bronzingNasturtium microphyllum (onerow yellowcress); leaves, showing bronzing.©Trevor James/Hamilton, New Zealand-2014
Nasturtium microphyllum (onerow yellowcress); upright flowering habit.
TitleUpright flowering habit
CaptionNasturtium microphyllum (onerow yellowcress); upright flowering habit.
Copyright©Trevor James/Hamilton, New Zealand-2014
Nasturtium microphyllum (onerow yellowcress); upright flowering habit.
Upright flowering habitNasturtium microphyllum (onerow yellowcress); upright flowering habit.©Trevor James/Hamilton, New Zealand-2014
Nasturtium microphyllum (onerow yellowcress); fruit capsules.
TitleFruit capsules
CaptionNasturtium microphyllum (onerow yellowcress); fruit capsules.
Copyright©Trevor James/Hamilton, New Zealand-2014
Nasturtium microphyllum (onerow yellowcress); fruit capsules.
Fruit capsulesNasturtium microphyllum (onerow yellowcress); fruit capsules.©Trevor James/Hamilton, New Zealand-2014
Nasturtium microphyllum (onerow yellowcress); fruit capsules.
TitleFruit capsules
CaptionNasturtium microphyllum (onerow yellowcress); fruit capsules.
Copyright©Trevor James/Hamilton, New Zealand-2014
Nasturtium microphyllum (onerow yellowcress); fruit capsules.
Fruit capsulesNasturtium microphyllum (onerow yellowcress); fruit capsules.©Trevor James/Hamilton, New Zealand-2014
Nasturtium microphyllum (onerow yellowcress); single row of seeds in fruit capsule.
TitleSeeds in fruit capsule
CaptionNasturtium microphyllum (onerow yellowcress); single row of seeds in fruit capsule.
Copyright©Trevor James/Hamilton, New Zealand-2014
Nasturtium microphyllum (onerow yellowcress); single row of seeds in fruit capsule.
Seeds in fruit capsuleNasturtium microphyllum (onerow yellowcress); single row of seeds in fruit capsule.©Trevor James/Hamilton, New Zealand-2014

Identity

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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 Invasiveness

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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 Tree

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  • Domain: Eukaryota
  •     Kingdom: Plantae
  •         Phylum: Spermatophyta
  •             Subphylum: Angiospermae
  •                 Class: Dicotyledonae
  •                     Order: Capparidales
  •                         Family: Brassicaceae
  •                             Genus: Nasturtium
  •                                 Species: Nasturtium microphyllum

Notes on Taxonomy and Nomenclature

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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. 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. 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.

Description

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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.

Plant Type

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Broadleaved
Herbaceous
Perennial
Seed propagated
Vegetatively propagated

Distribution

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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.

In New Zealand, N. microphyllum is more common further south than N. officinale (Mason, 1982; Coffey and Clayton, 1988).

Distribution Table

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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/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Asia

AfghanistanPresentNativeUSDA-ARS, 2013
IndiaPresentNativeUSDA-ARS, 2013
-Himachal PradeshPresentNativeUSDA-ARS, 2013
-Jammu and KashmirPresentNativeUSDA-ARS, 2013
IranPresentNativeUSDA-ARS, 2013North of Iran (Naqinezhad, 2006)
JapanPresentIntroducedUSDA-ARS, 2013
PakistanPresentNativeUSDA-ARS, 2013Northwest Frontier Province only (Flora of Pakistan, 2013)
YemenPresentIntroducedUSDA-ARS, 2013

Africa

Congo Democratic RepublicPresentIntroducedUSDA-ARS, 2013
EritreaPresentIntroducedShaw, 1947
EthiopiaPresentIntroducedUSDA-ARS, 2013
KenyaPresentIntroducedUSDA-ARS, 2013
MoroccoPresentNativeUSDA-ARS, 2013
South AfricaPresentIntroducedShaw, 1947
UgandaPresentIntroducedUSDA-ARS, 2013

North America

CanadaPresentPresent based on regional distribution.
-British ColumbiaPresentIntroducedUSDA-NRCS, 2013
-ManitobaPresentIntroducedUSDA-NRCS, 2013
-New BrunswickPresentIntroducedUSDA-NRCS, 2013
-Newfoundland and LabradorPresentIntroducedUSDA-NRCS, 2013
-OntarioPresentIntroducedUSDA-NRCS, 2013
-Prince Edward IslandPresentIntroducedUSDA-NRCS, 2013
-QuebecPresentIntroducedUSDA-NRCS, 2013
Saint Pierre and MiquelonPresentIntroducedUSDA-NRCS, 2013
USAPresentPresent based on regional distribution.
-AlabamaPresentIntroducedUSDA-NRCS, 2013
-AlaskaPresentIntroducedUSDA-NRCS, 2013
-ArkansasPresentIntroducedUSDA-NRCS, 2013
-GeorgiaPresentIntroducedUSDA-NRCS, 2013
-HawaiiPresentIntroducedUSDA-NRCS, 2013
-IdahoPresentIntroducedUSDA-NRCS, 2013
-KentuckyPresentIntroducedUSDA-NRCS, 2013
-MainePresentIntroducedUSDA-NRCS, 2013
-MassachusettsPresentIntroducedUSDA-NRCS, 2013
-MichiganPresentIntroducedUSDA-NRCS, 2013
-MinnesotaPresentIntroducedUSDA-NRCS, 2013
-MississippiPresentIntroducedUSDA-NRCS, 2013
-NebraskaPresentIntroducedUSDA-NRCS, 2013
-New HampshirePresentIntroducedUSDA-NRCS, 2013
-New MexicoPresentIntroducedUSDA-NRCS, 2013
-New YorkPresentIntroducedUSDA-NRCS, 2013
-North CarolinaPresentIntroducedUSDA-NRCS, 2013
-OregonPresentIntroducedUSDA-NRCS, 2013
-PennsylvaniaPresentIntroducedUSDA-NRCS, 2013
-TennesseePresentIntroducedUSDA-NRCS, 2013
-VirginiaPresentIntroducedUSDA-NRCS, 2013
-WisconsinPresentIntroducedUSDA-NRCS, 2013

South America

ArgentinaPresentIntroducedUSDA-NRCS, 2013Entre Rios
ChilePresentIntroducedUSDA-ARS, 2013

Europe

AustriaPresentNativeUSDA-ARS, 2013
BelgiumPresentNativeUSDA-ARS, 2013
Czech RepublicPresentNativeUSDA-ARS, 2013
DenmarkPresentNativeUSDA-ARS, 2013
FrancePresentNativeUSDA-NRCS, 2013
GermanyPresentNativeUSDA-ARS, 2013
IrelandPresentNativeUSDA-ARS, 2013
ItalyPresentNativeUSDA-ARS, 2013
NetherlandsPresentNativeUSDA-ARS, 2013
PolandPresentNativeUSDA-ARS, 2013
SloveniaPresentNativeUSDA-ARS, 2013
SpainPresentNativeUSDA-ARS, 2013
SwedenPresentNativeUSDA-ARS, 2013
SwitzerlandPresentNativeUSDA-ARS, 2013
UKPresentNativeUSDA-ARS, 2013

Oceania

AustraliaPresentIntroducedUSDA-ARS, 2013
-New South WalesPresentIntroducedWeeds of Australia, 2013Some parts of eastern NSW
-QueenslandPresent, few occurrencesIntroducedUSDA-NRCS, 2013South eastern parts
-South AustraliaPresentIntroducedUSDA-NRCS, 2013South eastern parts
-TasmaniaPresent, few occurrencesIntroducedUSDA-ARS, 2013South eastern parts
-VictoriaPresentIntroducedUSDA-ARS, 2013Southern and eastern parts
New ZealandPresentIntroducedUSDA-ARS, 2013

History of Introduction and Spread

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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.

Introductions

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Introduced toIntroduced fromYearReasonIntroduced byEstablished in wild throughReferencesNotes
Natural reproductionContinuous restocking
Australia 1869 Yes No Australia’s Virtual Herbarium (2013); Royal Botanic Gardens Sydney (2004); Royal Botanic Gardens Sydney (2013) Tasmania

Risk of Introduction

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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.

Habitat

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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 List

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CategoryHabitatPresenceStatus
Freshwater
Irrigation channels Principal habitat Natural
Lakes Principal habitat Natural
Ponds Principal habitat Natural
Rivers / streams Principal habitat Natural
Terrestrial-natural/semi-natural
Riverbanks Present, no further details
Wetlands Principal habitat Natural

Biology and Ecology

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Genetics

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).

Reproductive biology

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.

Growth

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.

Longevity

N. microphyllum is perennial and, since it can reproduce asexually from vegetative stems, can probably live for several years (Howard and Lyon, 1952b).

Associations

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

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.

Climate

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ClimateStatusDescriptionRemark
Cf - Warm temperate climate, wet all year Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year

Notes on Natural Enemies

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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 Dispersal

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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 introduction

Accidental contamination of aquarium plants or animals could possibly spread the species.

Intentional introduction

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.

Pathway Causes

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CauseNotesLong DistanceLocalReferences
Aquaculture Yes Yes Howard and Lyon, 1952b
Crop production Yes
Flooding and other natural disasters Yes Weeds of Australia, 2013
Hitchhiker Yes

Pathway Vectors

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VectorNotesLong DistanceLocalReferences
Aquaculture stock Yes Yes Howard and Lyon, 1952b
Land vehicles Yes
Machinery and equipment Yes

Impact Summary

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CategoryImpact
Environment (generally) Positive and negative

Impact

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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 Impact

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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 Factors

Top of page Invasiveness
  • Proved invasive outside its native range
  • Has a broad native range
  • Long lived
  • Fast growing
  • Has high reproductive potential
  • Reproduces asexually
Impact outcomes
  • Modification of natural benthic communities
  • Modification of nutrient regime
  • Reduced amenity values

Uses

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Economic value

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.

Social benefit

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.’

Uses List

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Human food and beverage

  • Vegetable

Similarities to Other Species/Conditions

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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 Control

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Biological control

Biological control would not be tolerated in most countries, since many people collect and consume wild-growing watercress.

Chemical control

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).

 

References

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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

Bleasdale JKA, 1964. The flowering and growth of watercress (Nasturtium officinale R. Br.). Journal of Horticultural Science, 39:277-283

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02/10/13: Original text by:

Ian Popay, consultant, New Zealand, with the support of Landcare Research.

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