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 Add this item to the list   Myriophyllum aquaticum


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 Author(s):(Vell.) Verdc. 
 Vernacular names:Parrot-feather, Parrots-feather (UK); Parelvederkruid (NL) 
 Synonyms:Myriophyllum brasiliense Cambess.; Myriophyllum proserpinacoides Gillies; Enydria aquatica Vell. 
 EPPO code:MYPBR (M. aquatica) 
 Plant code - standard list:FB2497 
 Botanical thesaurus:
 Factsheet link (English):
 Factsheet link (French):
 Factsheet link (Dutch):


Roots and stem
 Description of subterranean parts:rhizomes 
 Description of stem:weakly trailing, glaucous, rooting freely from lower nodes, glabrous. 
Fruit and seeds
 Description of seed:mericarps cylindrical, slightly wider towards base, apex oblique, with an indistinct thickened rim, otherwise smooth, rounded on dorsal surface. 
 Description of fruit:fruit (immature) on pedicel 0.7-0.8 mm long, cylindrical to ovoid. 
 Length of seed (mm) :1.7 
 Description of propagule:In Europe there are exclusively female plants present, only vegetative propagation by detached (parts of) rhizomes or stems is possible. 
 Description of leaf:Submerged leaves in whorls of (4-) 5-6, without stipules, flaccid, usually much longer than internodes, oblanceolate in outline, rounded at apex, pectinate, with 25-30 linear pinnae up to 0.7 cm long, the lower leaves usually decaying rapidly. Emergent leaves glaucous and densely covered by translucent hemisperial glands, flaccid, usually much longer than internodes, in whorls of (4-) 5-6, erect near apex, spreading in lower parts, narrowly oblanceolate in outline, rounded at apex, pectinate, with (18-) 24-36 pinnae in the upper for-fifths (lower 5-7 mm of rachis naked), pinnae linear to subulate, 4.-5.5 mm long, 0.3 mm wide, tips very apiculate, sligtly in curved. Numerous hydathodes at base of leaves, 0.5-1 mm long. 
alternate no
opposite no
decussate no
whorled yes
 Description of inflorescence:Plants dioecious, male much less common than female throughout introduced range. In Europe exclusively female flowers (in Germany also plants with male flowers in culture). Inflorescence an indeterminate spike with flowers singly borne in axils of upperemergent leaves, subtended by 2 bractioles subulate, 1.2 - 1.5 mm long with (1-) 2 short teeth in the lower-third, sometimes almost trifid. 
 Description of flower:Male flowers tetramerous, sessile at first, with pedicels to 4 mm long usually developing at anthesis; sepals 4, ovate-deltoid, very weakly denticulate, smooth; petals weakly hooded and keeled; stamens 8; styles 0. Female flowers tetramerous, on pedicel 0.2-0.4 mm long; sepals 4, white, deltoid, denticulate with one to several small teeth on each margin, smooth (first persisting, erect, withering at maturity); stamens 0; styles clavate, very short, stigmas subsessile, oblong, recurved, persistent. 
Colour of flower:
white no
yellow yes
orange no
pink no
brown no
red no
purple no
blue no
green no
 Description of stamens:"filaments 0.1 mm long at anthesis, lengthening later to up to 1.2 mm; anthers yellow, linear-oblong (1.8-) 2.0-2.7 mm long, 0.2 mm wide, non-apiculate." 
 Description of ovary:inferior, pyriform, 4-celled, 0.6-0.7 mm long, 0.6 mm wide, 4-ribbed longitudinally between sepals. 
 Length of styles (mm):0.1 - 0.2 
 Description of stigmas:white, densely fimbriate. 

Additional information

 Similar species:1 Population in slow-flowing or still water and shoot emergent; aerial or emergent leaves ± glaucous and densely covered by translucent hemisperical glands; only ? flowers represented (populations of M. aquaticum in fast-flowing water may lake shoot apices); populations in fast-flowing water should be assumed not to be M. aquaticum unless there is very good justification M. aquaticum / - Population in still, slow-flowing or fast-flowing water; shoot apices not emergent or if so, then not ± glaucous and densely covered by translucent hemi-spherical glands; or with upper flowers ? and lower ? 2 // 2 Leaves ? 10 mm long with 8 pairs of segments 3 / - Leaves > 10 mm long with > 8 pairs of segments 5 // 3 Submerged leaves fairly stiff and curved to point along line of stem, usually reddish and shorter than internodes M. verrucosum / - Leaves flaccid, not reddish, shorter or longer than internodes 4 // 4 Leaves (3-)4 to a whorl; usually shorter than internodes M. alterniflorum / - Leaves (4-)5-6 to a whorl; usually much longer than internodes M. aquaticum // 5 Leaves longer than internodes, ? 20 mm long with > 10 pairs segments 6 / - Leaves longer than or shorter than internodes, less than or more than 20 mm long, with 3-20 pairs of segments; turions never produced 7 M. aquaticum may occur in submerged form in fast-flowing water and there is apparently no guidance on distinctions between this, M. verticillatum and M. spicatum under such circumstances. // 6 Mid-stem leaves 1.4-4(-5.5) times long as the internodes; clavate turions developing on the lower stems in late summer; emergent inflorescence with pinnate bracts; plants lacking any reddish tinge M. verticilatum / - Mid-stems leaves 0.5-1.5(-2.3) times as long as the internodes turions absent; emergent inflorescence with simple bracts; plants often with a reddish tinge; lower leaves shorter than the internodes M. spicatum // 7 At least some leaves not in whorls, ± alternate; emergent leaves serrate-denticulate M. heterophyllum / - All leaves in worls; emergent leaves lacking 8 // 8 Mid-stem leaves 3-26 mm long, with 6-18 segments¹ M. alterniflorum / - Mid-stem leaves (-8)15-45 mm long, with (13-) 15-41 segments M. spicatum // 1Plants with leaves that are 8-26 mm long and have 13-18 segments could be either M. alterniflorum or M. spicatum. 
 Look-alike link:

Distribution information

 Original distribution:South America. 
 Current distribution:Asia: Cambodia, Java, Japan, Malaysia, Phillippines, Thailand, Vietnam. Europe: Austria, Belgium, France, Germany, Hungary, Ireland, Italy, Portugal, UK, The Netherlands. Africa: Madagascar, South Africa, Zimbabwe. North America: Mexico, USA, Hawaii. Central America: Nicaragua. South America: Argentina, Brazil, Chile, Paraguay, Peru, Uruguay. Oceania: Australia, New Zealand 
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Life cycle:
annual no
perennial yes
monocarp no
biennial no
Flowering time in Europe:
January no
February no
March no
April no
May no
June yes
July yes
August no
September no
October no
November no
December no
 Hardiness:very hardy. 
 Habitat requirements:M. aquaticum is mainly found growing in low-lying areas, in shallow waters and on muddy substrates, but also recorded at higher altitudes from a high as 3250 m in Peru and 1900 m in Brazil. The weed strongly favours eutrophic conditions, it prefers warm areas over hotter tropical regions. 
 Ecological amplitude:it tolerates coastal or saline-influenced waters, to 3.3 parts per thousand salinity. 
 Habitat elsewhere:in lakes, ponds, marshes, fens and irrigation channel systems. 
 Habitat in the Netherlands:in shallow, eutrophic water of ponds, ditches, channels and canals. 
 Palatability:cattle and waterfowl graze the shoots, but standard biocontrol such as grass carp do not appear to find the plant palatable. 

Invasiveness, risk and control

Dispersal mechanism:
wind ?
water variable
others variable
endozoochorous variable
ectozoochorous variable
 Host, diseases and pest information:Microsphaera alphitoides (Fungus). Listronotus marginicollis (Coleoptera). Lysathia flavipes and L.ludoviciana (Coleoptera). 
 Invasive behavior information:The weed is particularly a problem in irrigation channel and riversystems (in California: it infested 24% of irrigation channel systems in 1985, with 914 km of waterway affected) and it is a rice weed in Indonesia and Cambodia. It changes the physical and chemical conditions in lakes and water systems; its stems float out over the surface to form a dense tangled raft of plant material, from which the emergent shoots arise to give an impenetrable weed problem. Small fragments root easily in mud to establish new colonies. M. aquaticum can have detrimental impacts, including interference with flow of irrigation water, hydro-electric power production, fisheries, recreation and increased risk of health hazards( increased incidence of mosquitoes). 
 Control:mechanical control: is rarely effective because of the plants ability to regrow rapidly from shoots fragments. However, more effective harvesting systems that remove the biomass and nutrient reserves accumulated in the emergent tissues may be an effective controle measure. Chemical control: is effective by herbicides. Biological control: remains at experimental stage. In 1985 the direct control expenditure on this weed in Californiawas $ 215 000 over a 2-year period. 
 Risk assessment for the Netherlands:dispersal mainly by the aquatic plants trade for aquaria and ponds. 

Link to other websites / databases

 Link to other websites_Url:


 Pest Risk Analysis: