Free Floating Aquatic Weed Control

Your Guide to Identifying & Controlling Free Floating Aquatic Weeds

There are three common types of Free Floating Aquatic Weeds

1. “Duckweed” or Lemna
Duckweed is a very common, tiny, free floating aquatic plant, with leaves varying from less than 1mm up to 1cm in size. Duckweed appears as a green cover on the waters surface and is an indication of nutrient-enriched conditions. It grows rapidly in stationary and slow moving water bodies, especially where nutrient levels are high. If not treated, it can double in numbers within five to seven days.

2. “Azolla” / Red Azolla / Green Azolla or Ferny Azolla
Azolla is another common free floating aquatic plant, with leaves varying in size from 1 to 2.5cm in diameter. Azolla appears in a greenish shade and can turn a reddish shade in the late afternoon or when exposed to full sunlight over a period of time. Azolla has a fern type leafed appearance with roots trailing below the waters surface. If not treated it can double in numbers within seven days.

3. Salvinia
Salvinia is a declared noxious free floating aquatic weed, in all states of Australia, with the plant measuring up to 20cm long and leaflets of 0.5-3cm wide. The leaves are covered with hairs that repel water and keep it from sinking. Salvinia is capable of choking a water body, it multiplies by fragmentation and can double the area it covers in five days. If not treated it can take over a water body, kill fish and rapidly affect water quality.


How to Control Free Floating Aquatic Weeds

Free floating aquatic weeds such as duckweed, lemna, azolla and in particular salvinia can be difficult to eradicate due to their rapid growth rates.

The main methods of control include, spray treatments, physical removal and a combination of both.

Spray treatments are most effective when the infestations are smaller rather than advanced. A combination of both a spray treatment and physical removal is best when the infestation is advanced and is covering 90 -100% of the water's surface.



Duckweed-Aquatic Algae

Azola - Aquatic Algae

Free Floating Weed Control



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Emergent Roots are anchored in the substrate with stems, leaves or flowers projecting above the water’s surface.
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Floating Attached Roots are attached to substrate. Stems, leaves or flowers may/may not be above water’s surface.
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Algae No distinguishable roots, stems or leaves.
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Free Floating Roots are not attached to substrate and float on the water’s surface.
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Submerged Growing below the water’s surface whether attached to substrate or not.
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