Anchored water hyacinth is an aquatic plant that forms dense mats in and across the surface of water bodies. It can invade still or slow-moving bodies of fresh water such as wetlands, dams and irrigation channels, and mud along river and creek banks.
Anchored water hyacinth can form a smothering mass of plant material in the water column and over the surface of a water body, having detrimental impacts on environmental, aesthetic and recreational values, and obstructing irrigation and navigation. The floating weed masses also harbour mosquitoes and can contribute to water loss through transpiration.
Anchored water hyacinth looks similar and is closely related to the floating noxious weed water hyacinth (Eichhornia crassipes), that does occur in waterways in eastern Australia and New South Wales (NSW).
Anchored water hyacinth is a native plant of Mexico, Central America, South America and Jamaica. It is currently found throughout Africa and parts of Texas, where it has been declared as a noxious weed and is the subject of active eradication campaigns. Due to the worldwide weed status of its close relative water hyacinth, anchored water hyacinth is a prohibited plant in many countries.
Anchored water hyacinth is not currently known to occur in NSW. In 2005 it was removed from a retail outlet in northern Sydney, but has not been reported since. It is prohibited from importation into Australia.
Anchored water hyacinth is able to reproduce both vegetatively (when new daughter plants grow from the stems of the parent plant) and by seed. Infestations spread when daughter plants or pieces of stem break away and move downstream. Whole sections of an infestation can break off and move during floods and periods of high water flow.
Flowering occurs in summer and autumn and seeds can be carried in water and mud, on vehicles and by birds. Seeds germinate in spring.
In countries where anchored water hyacinth is an established weed, humans have contributed to spread by growing it as an ornamental plant in ponds or aquariums and dumping unwanted plants in or near waterways.
Anchored water hyacinth can be distinguished from water hyacinth by its petioles (leaf stalks) which are slender - not inflated like the stems of water hyacinth.
Submerged stems are smooth and branched. Flowering stems are erect and stand 8–12 cm above the water.
Emergent leaves are variable in size, generally very rounded in shape, 5–16 cm long and 2–16 cm wide. Leaves growing below the water or in heavily shaded areas become elongated, between 6 and 20 cm long and about 1 cm wide.
Flowers are in spikes with several flowers along a hairy stem. The flowers are funnel-shaped with six toothed petals 1–3 cm long. The flowers are mostly white or lavender blue with deep purple centres. The uppermost petal has a distinct yellow spot. Individual flowers open for one day only.
Seeds are small and only 1–2 mm long.
Anchored water hyacinth is also similar to the native plant Monochoria cyanea - a subtropical species rarely found in NSW. In comparison anchored water hyacinth has larger flowers, a longer and denser flower head, a yellow spot on the uppermost petal, and more rounded leaves.
Anchored water hyacinth usually grows rooted in mud or clay beneath the water, and can reach the surface even when rooted at depths of up to 10–15 metres. It can also survive free-floating.
2006 edition prepared by Annie Johnson; 2012 edition reviewed by Rod Ensbey; Edited and prepared by Elissa van Oosterhout.
Department of the Environment (2011) Weeds in Australia, Eichhornia azura, Australian Government. Available at www.environment.gov.au
Early detection of anchored water hyacinth is critical to keeping Australia free of this serious weed. If you think you have found anchored water hyacinth contact your local council weeds officer immediately for assistance.
See Using herbicides for more information.
PERMIT 9907 Expires 31/03/2020
Glyphosate 360 g/L (Only products registered for aquatic use)
Rate: Up to 200 ml in 10 L of water
Comments: Spot spray application
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate
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State Prohibited Weed
The plant must be eradicated from the land and that land must be kept free of the plant