Eichhornia crassipes in the EPPO region
Eichhornia crassipes (Pontederiaceae) is an aquatic plant originating from South America. It is extensively traded for ornamental and aquarium purposes. It is naturalized and often found to be invasive in tropical and subtropical regions. Its common name is “water hyacinth” in English and “Jacinthe d’eau” in French. In the EPPO region, it is already invasive in Spain and Portugal. Because its distribution is still very limited, this plant can be considered a new emerging invader in Europe.
Geographical distribution
EPPO region: Israel, Portugal, Russia, Spain
Note: In the Paúl do Boquilobo Biosphere Reserve in Central Portugal, it forms dense floating mats over extensive areas of wetlands and is considered the most obvious threat to the ecosystem. The plant is also recorded as invasive in Spain in Caceres, Taragon, Castillon and Alicante.
Africa: Burkina Faso, Burundi, Cameroon, Congo, Côte d’Ivoire, Egypt, Equatorial Guinea, Ethiopia, Gabon, Ghana, Guinea, Guinea-Bissau, Kenya, Liberia, Madagascar, Malawi, Mauritius, Mozambique, Nigeria, Reunion, Rwanda, Senegal, Sierra Leone, South Africa, Sudan, Swaziland, Tanzania, Togo, Uganda, Zambia, Zimbabwe.
Asia: Bangladesh, Cambodia, China, Brunei Darussalam, India, Indonesia, Lebanon, Japan, Jordan, Laos, Malaysia, Maldives, Myanmar, Philippines, Singapore, Sri Lanka, Syria, Taiwan, Thailand, Viet Nam.
Caribbean: Bahamas, Cuba, Dominican Republic, Haiti, Jamaica, Puerto Rico.
Central America: Guatemala, Honduras, Nicaragua, Panama.
North America: Mexico, USA.
Oceania: American Samoa, Australia, Cook Islands, Fiji, French Polynesia, Guam, Marshall Islands, Federated States of Micronesia, Nauru, New Caledonia, New Zealand, Northern Mariana Islands, Palau, Papua New Guinea, Samoa, Solomon Islands, United States minor outlying islands, Vanuatu.
South America: Brazil, Chile, Colombia, Costa Rica, Ecuador, Peru, Venezuela.
Morphology
E. crassipes is a free-floating aquatic macrophyte growing generally to 0.5 m in height, forming dense floating mats. Leaves are ovate to circular, 10-20 cm in diameter, thick and rise above the water surface. The stalk is erect to 50 cm long and carries at the top a single spike of 8-15 purplish blue or lavender to pinkish flowers.
Biology and Ecology
It is considered one of the most serious weeds in many tropical, warm and temperate freshwater habitats worldwide. It has the highest growth rate of any saltwater, freshwater or terrestrial plant. It reproduces both vegetatively and sexually, although vegetative reproduction is more important. Stolon buds are distributed by water currents, winds and boat traffic.
Habitats
E. crassipes grows in shallow temporary ponds, wetlands and marshes, sluggish flowing waters, lakes, reservoirs and rivers.
Environmental requirements
E. crassipes exists in Europe, but does not flourish in some countries as a result of the climatic conditions. It can tolerate extremes of water level fluctuations and seasonal variations in flow velocity, as well as extreme variations in nutrient availability, pH, temperature and toxic substances. This plant is susceptible to frost and salinity can limit or modify its distribution.
Impacts
E. crassipes is one of the world’s worst weeds. It forms thick mats that cover rice paddies, clog irrigation channels, impede navigation, halt fishing, favour the destruction of buildings during floods and the development of disease-transmitting mosquitoes.
Control
Control strategies must address both watershed management and direct weed control.
Small infestations can be controlled by pulling and harvesting machines may also be utilised.
Regulatory status in Europe
In Scotland (UK), the Scottish Wildlife and Countryside Act prohibits the release of E. crassipes into the wild. In Portugal, trade, transport and possession of the plant are prohibited according to the Decreto Lei 565/99.
Sources
University of Coimbra (PT) – Decreto Lei 565/99
The Wildlife and Countryside Act 1981 (Variation of Schedule) (Scotland) Order 2005
United Nations Educational, Scientific and Cultural Organization – Biosphere Reserve Information
Global Invasive Species Database