Myriophyllum aquaticum | Parrot's-feather



Conservation status

Not Assessed

Legal status

Third Schedule listed species under Regulations 49 & 50 in the European Communities (Birds and Natural Habitats) Regulations 2011. (Note: Regulation 50 not yet enacted).

Listed as a schedule 9 species under Articles 15 & 15A of the Wildlife Order (Northern Ireland) 1985 (Article 15A not yet enacted).

Regulated invasive  species of Union concern under the European Regulation on the prevention and management of the introduction and spread of invasive alien species [1143/2014].

First reported in the wild



Invasive species - risk of High Impact

Irish status


Introduction pathways - 1

Escape from Confinement

Introduction pathways subclass - 1

Ornamental purpose

Invasive score


NAPRA Ireland risk assessed

Yes. This species underwent a  Non-native species APplication based Risk Analysis  in 2014.

Overall risk of this species to Ireland is categorised as: MODERATE to MAJOR with a MEDIUM level of confidence.

Overall conclusion summary:  Myriophyllum aquaticum has already demonstrated its ability to establish under natural conditions in Ireland. Its capacity to cause negative impacts in a number of countries where it has established (including Britain) has also been documented (refer to elsewhere in this risk assessment). What is uncertain is how invasive this plant may or may not become should it become established in other suitable waters in Ireland. To date, there are only two known populations in the country, where the plant could be considered invasive. Therefore, with the limited information available to inform this risk assessment and in acknowledgement of the knowledge gaps that exist, the overall risk of this organism in Ireland is presently considered to be ‘moderate to major’ with ‘medium confidence’.

One cautionary note is that, in Britain, Myriophyllum aquaticum can cause a range of detrimental environmental and economic impacts and this may become evident in Ireland if the plant establishes in any natural open water systems where further systemic spread can more easily occur.

View the full risk assessment:

Species Biology


A freshwater aquatic perennial plant. Its blue-green colour and feather-like leaves seen most often emerged from the water year round make this a distinctive water plant. The feather like finely divided paired leaves are arranged in whorls of 4-6 on stems up to 2 meters long. Stems break easily with brown roots present around nodes. Inconspicuous whitish female flowers found at the base of the emerged leaves in whorls of 4-6 generally flowering July-August.Unlikely to be found in fast flowing water but where present it is mostly likely to be submerged. 


To date no impacts recorded in Ireland but that is likely due to its limited distribution and low abundance at sites (Millane & Caffrey, 2014). However much like other aquatic plants that form dense stands, it is likely to exclude native plants when abundances are high.


Inland surface waters


All plants outside its native range to data have been female so it reproduces solely by fragmentation and vegetative reproduction (Stace, 1997).

Pathway and vector description

Widely sold as an oxygenator or ornamental plant and present in artificial watercourse, ponds and aquaria (Millane & Caffrey, 2014). Subsequently introduced into the wild, by escape during flooding or attached to waterfowl, or deliberately introduced. The potential exists for it to be further dispersed by human mediated mechanisms within Ireland.

Mechanism of impact

Competition, Bio-fouling

Management approach

There is currently an EU wide ban on the sale, growing and keeping of this plant (European Commission, 2017).


Public awareness campaigns highlighting Myriophyllum aquaticum should be directed at gardeners and water users. Education on the identification of and biosecurity measures necessary is critical in preventing the spread of this species.


Where possible the infestation should be isolated. Dams or weighted nets can be used depending on site specifics (EUPHRESCO DeCLAIM, 2011).


Hand-pulling can be carried out on small infestations (EUPHRESCO DeCLAIM, 2011). The method is effective if the entire plant is removed but it is labour intensive and time consuming.


Cutting should be avoided as it does not provide control and may enable spread (EUPHRESCO DeCLAIM, 2011). Methods such as raking, chaining, using excavators with weed buckets that remove the root can help to provide control. Capture nets should be put in place before any mechanical removal commences.


Spraying with Glyphosate (Monteiro and Moreira, 1990) should be carried out from early June (EUPHRESCO DeCLAIM, 2011). M. aquaticum has a waxy cuticle so the addition of an adjuvant is necessary for effective control (EUPHRESCO DeCLAIM, 2011).  IMPORTANT: Seek up-dated professional advice on use of herbicides especially when using in or near waterbodies or courses. 


Dyes can be used in the Spring in still water (EUPHRESCO DeCLAIM, 2011). However, this is a non-selective method and should be reserved for areas of heavy monocultural infestation.

Consideration can be given to planting trees and shrubs in problem areas exploiting M. aquaticum's susceptibility to shading (EUPHRESCO DeCLAIM, 2011).

This species does not grow well in water deeper than 50cm so increasing water depth after the use of one of the other control methods may help maintain control (EUPHRESCO DeCLAIM, 2011).

Broad environment


Habitat description

Slow moving, freshwater including canals, lakes and ponds (Millane & Caffrey, 2014).

Species group


Native region

South America


World distribution(GBIF)

Irish distribution

Established - Localised. Locally quite scarce at a most sites in Ireland, except at Fota Island, Co. Cork and Kilmeaden, Co. Waterford where dense stands are found (Millane & Caffrey, 2014). Distribution and abundance may be limited by climatic conditions (Millane & Caffrey, 2014).

Native distribution

Native to South America but widely introduced elsewhere (Preston et al., 2002).

Temporal change

Date of first record category


Fifty year date category


Records submitted to Data Centre in 2024

The following map is interactive. If you would prefer to view it full screen then click here.

How can you help

Report any sightings to the National Biodiversity Data Centre. Do not purchase this plant or grow in outdoor ponds. Dispose of garden waste responsibly and never dump aquatic plants in water ways.



EUPHRESCO DeCLAIM (2011) EUPHRESCO DeCLAIM Final report. A State-of-the-art June 2011 Myriophyllum aquaticum (Vell.) Verdcourt. Plant Protection Service Aquatic Ecology and Water Quality Management Group, Wageningen UR. Centre for Ecology and Hydrology, Wallingford. Site accessed 30 August 2017.

European Commission (2017) Invasive Alien Species of Union Concern. European Union, Luxembourg.

Ferreira, T &  Moreira, I (1990) Weed evolution and ecology in drainage canals of central Portugal. Proceedings of the 8th International Symposium on Aquatic weeds, Uppsala, Sweden, 13-17 August 1990., pp. 97 - 102. Site accessed 30 August 2017.

Millane, M. & Caffrey, J. (2014) Risk Assessment of Myriophyllum aquaticum (Vellozo) Verdcourt – Parrot’s Feather. Prepared for Inland Fisheries Ireland and the National Biodiversity Data Centre.

Preston, C.D., Pearman, D. A. & Dines, T. D. 2002. New atlas of the British and Irish flora. An atlas of the vascular plants of Britain, Ireland, the Isle of Man and the Channel Islands, Oxford University Press.

Stace, C. (1997). New Flora of the British Isles 2nd Edition. Cambridge University Press, Cambridge.

Risk Assessment of Myriophyllum aquaticum

Global Invasive Species Database

Invasive Alien Species in Northern Ireland

Inland Fisheries Ireland