Know Your Weeds: Amazon Frogbit

Amazon Frogbit (Limnobium laevigatum) is a fast-spreading aquatic plant that poses a serious biosecurity risk to waterways across the Wet Tropics. Originally introduced for ornamental use in aquariums and ponds, it has become highly invasive, forming dense mats that smother native aquatic vegetation, reduce oxygen levels, and disrupt freshwater ecosystems.

WHAT IS IT?

Amazon Frogbit (Limnobium laevigatum) is a floating aquatic plant, native to Central and South America. It was introduced for use in aquariums and ponds but has become highly invasive in many regions, including parts of Queensland.

WHY IS IT A PROBLEM?

Amazon Frogbit forms dense mats on water surfaces, smothering native aquatic plants and reducing oxygen levels in the water. This disrupts ecosystems, harms aquatic life, and can block waterways, impacting recreational activities and water management infrastructure.

CHARACTERISTICS

Amazon Frogbit has bright green, rounded leaves that float on the water’s surface, forming rosettes. Its roots dangle below the surface, creating a dense network. The plant produces small white flowers and spreads rapidly through vegetative reproduction. It thrives in tropical and subtropical climates, and can impact ponds, dams, and slow-moving
waterways.

HOW TO SPOT IT ON YOUR PROPERTY

Look for floating clusters of round, bright-green leaves with spongy undersides. The roots are long and feathery, hanging below the water. It often forms thick mats that cover the water surface. Amazon frogbit currently occurs in the Barron River catchment between Yungaburra and Cairns. All detections in other locations should be reported to your local government immediately.