History & Introduction
Native to Brazil, this aquatic floating plant was first Introduced to the United States in the 1884 as an ornamental plant for water gardens during the Cotton States Exposition in New Orleans. It now has a global distribution and is often regarded as one of the world’s worst invasive species.
While it can still be found for sale in the plant trade, it is regulated or prohibited in a number of places. Its propagation, sale, and/or distribution is now illegal in states such as Alabama, Arizona, Arkansas, California, Florida, and Louisiana, as well as countries such as New Zealand.
Currently, water hyacinth is a Tier 2 species within LIISMA. This means there are very few known locations of this species with a goal of regional eradication.
Identification
Habit: A free floating perennial herb with rosettes that can vary in size from a few inches to over 3ft in length. They are connected together by smooth horizontal stems (stolons).
Leaves: Thick, leathery, glossy leaves attached to thick and often have spongy, inflated stalks. Leaves are entire and broadly round or oval in shape, 4-8” in diameter.
Flowers: 8-15 showy lavender flowers, arranged in a spike that can reach 12” long. The uppermost petal of each flower is a bit larger with a bright yellow patch and a darker purple border.
Roots: Dark and purple-ish in color, feathery.
Fruit: a 3 chambered capsule with many very small, ribbed seeds. Seeds are formed in underwater withered flowers.
Phenology: Blooms occur late summer-early fall.
Habitat
All kinds of freshwater bodies (lakes, ponds, rivers, marshes, etc.). Water hyacinth is also extremely tolerant of waters polluted with heavy metals.
Dispersal
Spread of water hyacinth is largely via stolons producing daughter plants, as well as by plant fragmentation and budding. Water hyacinth can also produce numerous seeds, up to 3000 per plant. Daughter plants and seeds can travel through water bodies, on boots, in watercrafts, and by wildlife.
While water hyacinth does not seem to rely heavily on sexual reproduction, it may assist the plant’s introduction to novel areas. Their seeds can withstand drying and may remain viable for greater than 5 years. Invasion in new areas requires shallow water and suitable rooting medium. Water high in phosphates may enhance germination rates, and may therefore be especially susceptible to invasion.
Damage and Impact
Water hyacinth is one of the world’s fastest growing plants. Through it’s ability to reproduce asexually via stolons, water hyacinth populations can double in size in as little as two weeks, and can multiply to cover an entire acre of water in just a single growing season.
Dense monocultures of water hyacinth on the surface of water bodies can impact aquatic recreation, native plant species, and wildlife. Water hyacinth colonies can make paddling activities extremely difficult, and can get tangled up in boat propellers and fishing lines. By crowding out native vegetation, water hyacinth invasions can lead to a reduction in aquatic plant biodiversity, potentially impacting pollinators and other wildlife that rely on native aquatic plants for food and habitat. As well, increased surface cover on ponds and lakes can alter water physiology, such as reducing dissolved oxygen concentrations and harm native and economically important fish populations.
Water hyacinth populations can also reduce the flow of rivers and streams, which can increase the potential for flooding as they form makeshift dams. As well, this water stagnation can provide ideal breeding environments for mosquitoes.
Prevention
Preventing the spread of water hyacinth is the best and most cost effective means of control. Do not purchase or grow water hyacinth. If you already have water hyacinth in a water garden, consider hand pulling or removing the plant from your garden. If you have water hyacinth in an indoor aquarium that you no longer want, dispose of the plant and the entire contents of the aquarium in the trash.
Managing waters with high nutrient loads can increase their resilience against the invasion of water hyacinth, as well as other aquatic invasive species. Updating septic systems and following the NYS Nutrient Runoff Law (using phosphorus free fertilizer and not applying fertilizer between December 1st and April 1st) can aid in freshwater nutrient management.
If you come across water hyacinth on social media pages for plant sales swaps, engaging with and educating swappers and sellers on the impact of this plant can help to prevent its introduction and spread. You can even simply send them the link to this fact sheet!
Wherever you see water hyacinth growing in natural areas, please document it in iMapInvasives or iNaturalist.
Control
Historically, control of water hyacinth has been extremely fraught. Early research into management methods included blasting the plants with hot water, spraying plants with strong acids, coating plants in petroleum followed by incineration, and applying a saturated salt solution (this latter solution was effective, but extremely costly). As a means of biocontrol, hippopotamus were nearly introduced to the US to consume water hyacinth monocultures in Louisiana, but the proposed bill fell short by 1 vote.
Older and larger infestations of water hyacinth may be contained, and eradication may not be feasible.
Manual control: For smaller and novel infestations, hand pull the entire plant, being sure to remove any small plant fragments, and place the plant matter in thick contractor bags. Solarize bags and dispose in municipal waste. Do not compost.
Chemical control: Chemical methods may provide the strongest control for water hyacinth, using approved aquatic herbicides such as Rodeo or Habitat. A certified commercial aquatic pesticide applicator would be required to apply this treatment. See this fact sheet by the Exotic Plant Council for herbicide application recommendations.*
Biological: Three species of weevil including Neochetina bruchi, N. eichhorniae, and the water hyacinth borer Sameodes albiguttalis have been introduced to Louisiana, Texas, and Florida, as well as 20+ countries to control water hyacinth. The weevils feed on the plants and may introduce secondary pathogens which aid in the reduction of vegetative propagation as well as seed production. However, due to the relatively short life cycle and need for constant re-introduction of the weevils species, their overall impact on monocultures of water hyacinth is relatively low. Another biological control insect, the planthopper Megamelus scutellaris has been recently found to be host specific, but more research is needed to determine its success in water hyacinth control.
Native Alternatives
Pickerel weed (Pontederia cordata)
Northern blue flag iris (Iris versicolor)
White water lily (Nymphaea odorata)
Check out the new NYS DEC Guide to Water Gardening in New York State to learn more about aquatic invasive species and recommended native alternatives!
Citations
- https://link.springer.com/article/10.1007/s10750-020-04407-7
- https://doi.org/10.1016/j.sajb.2011.03.009
- https://acsess.onlinelibrary.wiley.com/doi/full/10.1002/jeq2.20022
- https://wric.ucdavis.edu/information/natural%20areas/wr_E/Eichhornia.pdf
- https://www.invasivespeciesinfo.gov/aquatic/plants/water-hyacinth
- https://myfwc.com/wildlifehabitats/habitat/invasive-plants/weed-alerts/water-hyacinth/
- https://wiki.bugwood.org/Eichhornia_crassipes#Economic_impacts
- https://en.wikipedia.org/wiki/Pontederia_crassipes#cite_note-FOOTNOTEKlorer190943-60
- Pérez, E. A., Coetzee, J.A., Ruiz Téllez, T., Hill, M.P. (2011). A first report of water hyacinth (Eichhornia crassipes) soil seed banks in South Africa. South African Journal of Botany.blastin
*When using herbicides, always read and follow label directions for rates, spraying conditions, and appropriate protective equipment, it’s the law. For more information regarding chemical control and potential permit requirements, please see our page on Managing an Invasion.
