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Azolla
(Azolla filiculoides)
A native fern that is found in stationary and slow moving water bodies. Under normal conditions, it is not considered a problem. Heavy infestations are usually an indication of high nutrient levels, and in these conditions it will form quite thick floating mats. Under these conditions it poses a danger to young children who might not realise that deep water can be hidden underneath. It gets its name Red Azolla due the to plant changing colour in late summer early autumn, from green to red.

Similar species
Could be confused with young Salvinia.

Distribution
Can be found in dams, lagoons and drainage channels in most parts of the Hunter and Central Coast.

Control measures
Physical control: This is an effective method of control, however complete eradication is difficult as plants may fragment during the removal process. These fragments may regenerate to form new plants. Once removed, plants can be used as mulch around trees or in the garden, as they cannot survive out of water.
Herbicide control: Not recommended. Contact your local weeds officer for more information.
Biological control: No agents available.

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Duckweed
(Lemna spp) (Wolffia spp) (Spirodela spp)
Duckweeds are tiny native plants that can be found in stationary and slow moving water bodies and are an important food source for birds and other aquatic organisms. Infestations are not normally a problem. Heavy infestations are an indication of high nutrient levels in the water.

Similar species
Should not be confused with other species.

Distribution
Can be found in many areas of the Hunter and Central Coast.

Control measures
Physical removal: Can be effective, removed plants can be used as garden mulch as they absorb nutrients from the water that will be released into the soil as they decompose.
Herbicide control: Not recommended.
Biological control: No agents available.

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Salvinia
(Salvinia molesta)
Salvinia is an introduced aquatic fern that can be found in stationary and slow moving water bodies, home aquariums and ornamental ponds. A quick growing plant that under ideal condition will double its mass in 3-7 days. A declared Category W2 Noxious plant under the Noxious Weeds Act 1993.

Similar species
Young plants could be confused with Azolla

Distribution
Widespread throughout the lower Hunter and Central Coast

Control Measures
Physical control: Mechanical removal can be effective, although it may be difficult to remove all plants by this method. As plants propagate from plant fragments, mechanical control can in some cases make the situation worse.
Herbicide control: There are registered herbicides available for the control of Salvinia.
Biological control: Agents have been released in the region, but due to our climatic conditions the insects do not reach high enough numbers to give control. The recommendation is that both mechanical and herbicide options be used, with the bulk of the plants being removed mechanically and then the remaining plants treated with a suitable herbicide.

Weed Information Sheet PDF

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Water Hyacinth
(Eichhornia crassipes)
Water Hyacinth is an introduced species that has adapted to our climatic conditions. It is a declared Category W2 Noxious plant under the Noxious Weeds Act 1993.

Similar species
No other similar species.

Distribution
It can be found in stationary or slow moving water bodies throughout the coastal regions of NSW.

Control measures
Physical control: Mechanical control of well-established infestations is difficult due to plants being tangled together, and the shear weight of mature Hyacinth. Young infestations can be removed successfully providing the area is not too large.
Herbicide control: There are registered herbicides available that will give control. The disadvantage being that following treatment plants will die and decompose making the water unfit for some uses, and the decomposition my trigger algal blooms.
Biological control: Insects have been released but unfortunately out climate does not allow sufficient numbers to breed up to control infestations.

Weed Information Sheet PDF

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Water Lettuce
(Pistia stratiotes)
Infestations of Water Lettuce are rare, but the plant has the potential to become a serious weed in this region. It is a Category W1 Noxious weed under the Noxious Weeds Act 1993.

Similar species
No similar species.

Distribution
Limited to Maitland and Port Stephens area.

Control Measures
Physical control: Removal of small infestations can be an effective method of control.
Herbicide control: There are registered herbicides available. Where infestations are dense, treatment may result in algal blooms as plant matter decays. Consult with your local Weeds Officer for latest treatment advice.
Biological control: No agents available.

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© 2004 Compiled by Ken Bunn, Coordinator, Hunter and Central Coast Weed Management Program.

Version #2, 2004

Design by Carlena Payne.
Email: carlenadesigns@hotmail.com