Aquatic weeds in the Ross River

Sagittaria/Delta Arrowhead (Sagittaria platyphylla) is a recent arrival to the Ross River, first found here in 2012. It is currently under a containment program in attempt to eradicate it from the river before it spreads throughout the region. Sagittaria is a highly invasive aquatic weed that can choke shallow waterways, including irrigation channels, blocking the flow of water, fish movement and recreational activities. The economic impact of Sagittaria is imense with farmers in the Murray-Darling basin collectively spending over $2 million on control each year to protect and restore irrigation channels.

Water Hyacinth (Eichhornia crassipes) Water hyacinth is a floating weed that forms a dense mat on the top of water bodies. It has light purple flowers and round, dark green leaves. Water hyacinth was originally introduced from Brazil to Australia as an ornamental pond plant. The dense floating mat restricts wildlife migration, depletes the oxygen levels of the water body and interferes with recreational use.

Cabomba/Fanwort (Cabomba caroliniana) grows completely underwater (except flowers) in slow moving or still water, forming a dense canopy below the surface of the water. The stems can grow to a massive 10m long and pose risk to swimmers who can become entangled.

Water Lettuce (Pistia stratiotes) is a floating water weed with spongy, fan-shaped leaves. It can form dense mats of material that shades out other plant species. Reproduction is by seed or runners which produce daughter plants. Water Lettuce has a rapid growth rate and if conditions are favourable it can quickly spread to cover an entire water body once introduced. The seed is generally spread between water bodies by water movement, natural or within water vessels or equipment.

Hymenachne (Hymenachne amplexicaulis) is a grass with long, wide leaf blades found in shallow water or the banks of rivers and can grow to 2.5 m high. Hymenachne forms dense stands and can increase the possibility of flooding by restricting water flow in drainage channels. The dense stands also pose risk to animals by restricting migration and reducing available habitat.

Salvinia (Salvinia molesta) is a free-floating, spongy water weed, found in slow moving water bodies with high temperature and nutrient loads. Salvinia impacts waterways by removing available habitat, shading the water column and reducing water quality by removing dissolved oxygen. Leaves are small and folded with tiny hairs on the surface and roots float freely in the water column. Salvinia does not produce flowers and therefore the only method of spread is believed to be transportation of live material between water bodies.