Water lettuce

• This free-floating, spongy aquatic perennial resembles a small floating open head of lettuce.
• Leaves are fan-shaped and covered with hairs.
• Roots are tufted, unbranched, feathery and up to 80cm long.
• Flowers are small, green and 10–20mm long.
• Fruit are egg-shaped, greenish and 1cm across. Each contains 4–15 seeds.
• Seeds are oblong, 2mm long and tapered at each end.

3D model

• View the 3D model to help you identify this plant. You can magnify the image and manipulate the view to inspect the plant from every angle.

• Prefers stationary or slow-flowing water.
• Is sensitive to frost.
• Grows best in water with high nutrient concentrations.

• Found in areas throughout eastern Queensland.

• Seeds germinate in muddy bottoms in late November to early December and float to the surface as seedlings.
• Flowering and reproduction begin early in the plant's life, about the fourth or fifth leaf stage, when plant densities are high.
• Propagation is by seed or by 20cm-long stolons (runners) that produce daughter plants; propagation by stolons is the most prevalent form of reproduction.
• Flowering occurs mostly during summer and early autumn.

Environmental

• Restricts water flow and increases water loss.
• Damages wildlife habitats, particularly when infestations are large.
• Serves as breeding grounds for mosquitoes.
• Transforms aquatic ecosystems.
• Shades out native aquatic plants.
• Reduces oxygenation of water.

Economic

• Interferes with irrigation and stock watering.

Social

• Interferes with boating when infestations are large.
• Degrades quality of swimming and fishing.

• Spread by daughter plants and seeds.
• Spread mostly by water movement.

• Find out how farmers can prevent weed spread.
• Find out how gardeners and outdoor enthusiasts can prevent weed spread.

Physical control

• Remove plants by hand for small areas or when numbers are low. Do this before flowering and seeding.

Mechanical control

• Use waterweed harvesters for larger areas.

Herbicide control

• Use herbicides as directed for effective control.
• For quicker plant death, spray in warmer months.

Read the water lettuce fact sheet for more about herbicide control and application rates.

Biological control

• The weevil Neohydromonus affinis has been introduced and exerts good control in some areas.
• Weevils have proved effective in dams from Bundaberg to Brisbane. The weevil life cycle takes about 3 months. Eggs are laid in fleshy leaves and larvae tunnel through plant tissue. Openings aid the entry of fungi and bacteria, causing tissue to rot.
• Biological control is most effective on large infestations but may take many years to achieve satisfactory control. To establish an effective breeding population of biological control agents, place infested plants in an area where water lettuce is concentrated.
• To find out more about these agents and protocols, contact your local government or contact us online, by phone or in person.

• Water lettuce is a category 3 restricted invasive plant under the Biosecurity Act 2014.
• You must not:
  • give it away
  • sell it
  • release it into the environment.

If you do any of these, penalties may apply.

• You must take all reasonable and practical measures that are under your control to minimise the biosecurity risks associated with dealing with water lettuce. This is part of your general biosecurity obligation (GBO).
• Each local government must have a biosecurity plan that covers invasive plants and animals in its area. This plan may include actions to be taken on water lettuce. Some of these actions may be required under local laws. Contact your local government for more information.