- Floating waterweed up to 65cm tall, with an extensive (up to 1m) feathery, black to purple coloured, root system.
- Leaves are round, bright to dark green and up to 5-10cm in diameter.
- Leaf stalks of young plants are swollen into spongy, bulbous structures; mature plants have elongated leave stalks.
- Flowers are light purple with a darker blue/purple and yellow centre, 4-6cm long, 3.5-5cm wide.
- Flowers are carried in dense spikes above the plant.
- Fruit capsules, 10-15mm long, containing up to 300 seeds.
- Seeds are egg-shaped, 0.5-1.5mm long.
- Prefers static or slow-flowing water with high nutrient concentrations.
- Used illegally as an ornamental plant in garden ponds.
- Native to Brazil.
- Infestations mostly in coastal Queensland and New South Wales.
- One of the worlds worst weeds, serious weed in Asia, Africa, North America and Papua New Guinea.
- Grows slowly during cooler winter months, starts rapid growth once temperatures rise.
- Grows from seed and through vegetative reproduction, vegetative reproduction is the most important way to of propagation.
- Seeds are produced in capsules at the base of each flower.
- Flowering can begin as early as October and continue through the summer months.
- Each of the flowers on a stalk remains open for one to two days before beginning to whither.
- When all the flowers on a plant have withered, the stalk gradually bends into the water and after about 18 days, seeds are released from capsules at the base of each dead flower and sink to the substrate.
- Seeds persist in the substrate for at least 15 years.
- Seeds and stem fragments spread mostly by water movement.
- Destroys native wetlands and waterways, killing native fish and other wildlife.
- Depletes water bodies of oxygen.
- Increases water loss.
- Provides breeding ground for mosquitoes.
- Large infestations stop the passage of boats by clogging the inlets of boat engine water-cooling systems.
- Degrades the quality of swimming and make fishing impossible.
- Interferes and damages infrastructure.
The best form of weed control is prevention. Treat weed infestations when they are small - do not allow weeds to establish.
Steps for weed prevention:
- Check your property regularly for suspect plants.
- Control new infestations before they spread and become a major problem.
- Don't dump weeds and garden waste in bush or parkland.
- Don't buy waterweeds or keep them in dams, ponds and aquariums.
- Know the weed status of any products or materials you are receiving. This includes fodder, grain, gravel, machinery, mulch, packing material, sand, soil, stock, vehicles and water.
- Clean your equipment, clothing, shoes, vehicles and machinery when leaving natural habitats and camping areas.
- Use a cleandown facility to blow, vacuum or wash dirt and seeds from vehicles, machinery and tools.
- Request a weed hygiene declaration from your suppliers.
- Ensure vehicles and machinery are clean before entering your property.
- Remove by hand or machine for small areas or when numbers are low, before flowering and set seeds in October.
- Large areas can be controlled with harvesters.
- Spraying an entire heavy infestation can cause water hyacinth to sink and result in pollution from the rotting weed. Avoid this by spraying strips of the weed or by mechanically removing much of the weed before spraying. For this reason it is vital to destroy scattered plants when they appear rather than delaying treatment until the entire water body has been choked. Heavy infestations on shallow water Diquat is the only herbicide registered for use in water storage areas used for human consumption. Note that 14 days must elapse after treatment before water can be consumed.
- In non potable water bodies water hyacinth can be treated with 2,4D, Diquat, Amitrole and Glyphosate.
- See the water hyacinth fact sheet (PDF, 388 kB) for herbicide control and application rates.
- Effective on large areas of water hyacinth but may take years to achieve satisfactory control.
- Four insect species have been introduced from South America and released by CSIRO since 1975. The two weevil species Neochetina eichhorniae and Neochetina bruchi, and the two moth species Niphograpta albiguttalis and Xubida infusella are present in Queensland.
- To establish an effective breeding population of biological control agents, infested plants should be placed in an area where the water hyacinth is concentrated. Your Local Government Office or Biosecurity Queensland can assist you with protocols and information on the collection site nearest to you.
- The presence of these biocontrol agents does not relieve landholders from their responsibility under Queensland legislation to control declared plants.
- A declared Class 2 species under the Land Protection (Pest and Stock Route Management) Act 2002.
- Taking for commercial use, introduction, keeping, releasing and supplying (including supplying things containing reproductive material of this pest) is prohibited without a permit issued by Biosecurity Queensland.
- Landholders are required to control declared pests on their properties.