Parrot's Feather

(Myriophyllum aquaticum)

What is parrot's feather?

Parrot's feather is a weed of freshwater ponds, dams and waterways.
Parrot's feather is a declared weed in Tasmania under the Tasmanian Biosecurity Act 2019 and associated Regulations. The importation, sale and distribution of parrot's feather are prohibited in Tasmania.

How to identify parrot's feather

Parrot's feather is a perennial (long-lived) freshwater herb with yellow-green stems reaching 5 m in length. The leaves are feathery in appearance and occur in whorls, becoming more densely packed towards the end of the stems. The flowers are small, white and unisexual; all plants in Australia have only female flowers.
Parrot's feather roots on the muddy bottom as well as on adjacent saturated mud and gravels, extending from the bank or rising up through the water to form a dense mass of tangled stems.
Rapid growth occurs in summer, slowing in winter and recommencing the following spring. Once fully established, an infestation does not grow greatly in extent, with the new growth replacing the previous year's stems which die off.

Parrots feather infestation, © Stephen Welsh; Parrot's feather.

Parrots feather stem, photo: Stephen Welsh

Stem of parrot's feather, © Stephen Welsh; Parrot's feather.

Close-up of Parrot's feather, © Kiowa Fenner.

Parrot's feather in Tasmania

Parrot's feather is recorded as an occasional weed of ponds, dams, drainage ditches and streams in Tasmania. Localised infestations occur in the north and north-west and around Bellerive in the south. Aquarium occurrences also occur.
Parrot's feather forms dense mats that impede water flow and limit recreational activities, while the floating mats which often break off from an infestation can block hydroelectric intakes and irrigation pumps, and small streams causing flooding.

What is the legal status of parrot's feather in your area?

The legal responsibilities of landholders and other stakeholders in dealing with parrot's feather are laid out in the Statutory Management Plan for Parrot's Feather.
Use Table 1 (Zone A municipalities)in the Statutory Management Plan for Parrot's Feather to find out whether this weed occurs in your municipality.

What you need to do

If you locate parrot's feather anywhere in Tasmania, or if you find a plant that you think could be parrot's feather, immediately contact Biosecurity Tasmania on 03 6165 3777 to report this weed.

Detailed management and control guidelines for parrot's feather can be found in the Parrot's Feather Control Guide. Refer also to Herbicides for Parrot's Feather Control. For further information see Weed Links and Resources.

See also

Parrot's Feather Control Guide

Plan your control program, this will save time and money in the long-run;
Consider the impact of your control methods on off-target species, especially if herbicides are used;
Carefully time your use of herbicide for best results (see Herbicides for Aquatic Weed Control for more information);
Coordinate your control program with neighbouring landholders where your weed problem crosses property boundaries;
Revisit and regularly inspect the site and ensure follow-up is undertaken.

Don't

Don't start your control program without first planning your approach;
Don't allow an infestation to become established. Get in early!
Don't rely on just one treatment: follow-up is essential.

Spread of parrot's feather

Only female flowered plants occur in Australia and reproduction of parrot's feather in Australia is solely by vegetative means.
The stems are fragile and stem fragments broken off by wave action or mechanical disruption float downstream and regenerate wherever they settle on sediments.
Long-distance spread also occurs via people dumping of aquarium material including parrot's feather in waterways.

Physical removal

Hand-pulling, subsurface cutting and draglines can be used to clear waterways of parrot's feather for long periods, but do not fully eradicate the weed.
When removing the weed, it is important to minimise the movement of stem fragments downstream to reduce the chance of spread.
Where possible, an infestation in a small pond or dam can be eradicated by completely removing all water and allowing the parrot's feather to dry out. The removed water must be carefully disposed of to avoid fragments of the weed being transferred to another water body.

Solarisation

Infestations in small dams can be effectively controlled by covering the dam with black plastic sheeting for several weeks to 'cook' the parrot's feather.

Chemical control

A number of herbicides are registered for use on parrot's feather in Tasmania. See Herbicides for Aquatic Weed Control for more information.

Herbicides for Parrot's Feather Control

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To the extent permitted by law, the Department of Natural Resources and Environment Tasmania (including its employees and consultants) excludes all liability to any person for any consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using information or material (in part or in whole) contained on this website.