Eichhornia crassipes | Water-hyacinth

Pre 2017

2017 - 2020


Legal status

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].


Invasive species - risk of Medium Impact

Irish status


Introduction pathways - 1

Escape from Confinement

Introduction pathways subclass - 1

Ornamental purpose

Invasive score


NAPRA Ireland risk assessed


Species Biology


Free floating aquatic plant with distinctive pale blue or violet flowers. The leaves are rounded, thick and have a waxy surface. Generally grows to 0.5m high (GISD, 2015). The leaf stalk is bulbous and holds the leaf above the surface of the water by means of its inner sponge like structure. Leaf stalks and leaves may be more elongated in crowded conditions (EPPO, 2008a). Leaves are arranged in a rosette. Usually 8-15 attractive flowers are borne on a single spike. The fibrous roots are 10-300cm long (GISD, 2015) and may be violet in colour. There are up to 70 lateral roots per centimetre (GISD, 2015).


Forms dense mats on still and slow moving freshwater bodies. These mats block out light to submerged and riparian plants and phytoplankton (Villamagna & Murphy, 2009). They also reduce water oxygen levels by preventing oxygen transfer between the air and water (Hunt & Christiansen, 2000 in Villamagna & Murphy). This can lead to fish kills when dissolved oxygen reaches critical levels (Ruiz Tellez et al., 2008). Outcompetes native plants by rapid growth rates and can double its population in as little as 10 days (Ruiz Tellez et al., 2008). Dense carpets can block waterways causing problems for agriculture, fisheries, hydropower plants and recreational use of the water. Dams in Africa are frequently forced to shut down due to the effects of large numbers of plants on hydropower equipment and water quality (EPPO, 2008a). The presence of these plants impacts rice production in particular by competing for space, inhibiting germination, reducing yields due to water loss through evapotranspiration and increasing harvesting costs when the plants block harvesters (EPPO, 2008a).


Inland surface waters


Propagates mainly by stolons (NNSS, 2010). Buds on the stolon produce a new plant. Production of these daughter plants allows rapid increases in population (EPPO, 2008a). May also reproduce by seed in some areas outside its native range e.g. In Spain's Guadiana River Basin (Ruiz Tellez et al., 2008).

Pathway and vector description

Cultivated in ponds to supply the horticulture industry and from there it escapes to the wider environment. Once established colonisation of new areas can occur through man's activities; attached to boats, fishing gear and other equipment. Since the plants are free floating they can disperse with conventional water flow and during flooding (EPPO, 2008a).

Mechanism of impact

Competition, Bio-fouling

Management approach

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

Focus should be on preventing establishment as it is very difficult to eradicate mainly beacuse of the constant reintroduction from horticultural sources (NNSS, 2010) and seed dormancy of up to twenty years (EPPO, 2009). Widely available to purchase on the internet (EPPO, 2008b). Awareness campaigns to aid in identification and early reporting as well as providing information about responsible disposal of plants (EPPO, 2008b).

In its native habitat it is controlled by grazing manatees (Trichechus manatus). However, there is no equivalent herbivore outside amazonia so when conditions are right populations increase rapidly (Ruiz Tellez et al., 2008).


Plants can be scooped out using heavy machinery such as backhoes with buckets (Ruiz Tellez et al., 2008) though care must be taken that barriers are in place to contain any escapees (EPPO, 2009). In harder to reach areas boats may be adapted to push plants to shore for removal. Clearances may need to be repeated twice annually.


There are glyphosate based products that are approved for aquatic use in Ireland. However, the plant's waxy cuticle may reduce the efficacy of the chemical. Repeat applications may be required.

An integrated approach using mechanical and chemical methods may give the best results (EPPO, 2009).

Broad environment


Habitat description

Freshwater lakes, ponds, slow moving streams, marshes, canals and ditches. 

Species group


Native region

South America

Similar species

Similar to Eichhornia azurea but E. Azurea is not free floating (EPPO, 2008a) and has submerged leaves (Q-bank, 2017). 


World distribution(GBIF)

Spread to over 50 countries on 5 continents (Gopal, 1987 in NNSS, 2010). Established in North America, South America, Asia, Carribean, Oceania, Africa. It is also recorded in Russia but doesn't do well (EPPO, 2008a). In Europe it is established in Croatia, France, Hungary, Germany, Portugal, Romania, and Spain. It is also has an occasional presence in Belgium, the Netherlands and the UK. 

Temporal change

Records submitted to Data Centre in 2022

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 or plant in your garden. Dispose of unwanted plants responsibly.



EPPO. (2009). PM 9/8(1) National regulatory control systems. Eichhornia crassipes, 39, pp 460-464. Site accessed 15 Aug 2017.

EPPO. (2008a). PM9/19(1) Invasive alien aquatic plants. EPPO Bulletin, 38(3) pp. 441-449. Site accessed 8 August 2017.

EPPO. (2008b). Pest risk analysis for Eichhornia crassipes. Risk assessment. Site accessed 10 August 2017.

European Commission. (2017). Invasive alien species of Union concern. European Union. Luxembourg.

Global Invasive Species Database (GISD). (2015). Species profile Eichhornia crassipes. Site accessed 8 August 2017.

Non-native Species Secretariat (NNSS). (2010). Eichhornia crassipes – Water Hyacinth. Risk assessment. Site accessed 9 August 2017.

Q-bank. (2017). Eichhornia crassipes (Mart.) Solms. Water Hyacinth. Factsheet. Site accessed 9 August 2017.

Ruiz Tellez, T et al. (2008). The Water Hyacinth, Eichhornia crassipes: an invasive plant in the Guadiana River Basin (spain). Aquatic Invasions, 3(1), pp.42-53. Site accessed 9 August 2017.

Tsiamis, K; Gervasini, E; Deriu, I; D'Amico, F; Nunas, A; Addamo, A; De Jesus Cardosa, A. (2017). Baseline distribution of invasive alien species of Union concern. Ispra (Italy): Publications office of the European Union, EUR 28596. Site accessed 10 August 2017.

Villamagna, AM; Murphy, BR. (2009). Ecological and socio-economic impacts of invasive water hyacinth (Eichhornia crassipes): a review. Site accessed 9 August 2017.

CABI Datasheet (

Global Invasive Species Database (

DAISIE Species Factsheet (

Additional comments

The Global Invasive Species Database lists this as one of the top 100 world's worst invasive species. However, its establishment seems to be limited by its inability to withstand the cooler temperatures of higher latitudes than its current range (NNSS, 2010). Most likely Ireland is currently too cold for it to establish here. However, there is anecdotal information that breeders in the Netherlands are developing more cold hardy varieties (NNSS, 2010).