Parrots feather

What does it look like?

Parrot's feather is a submerged, bottom-rooted perennial aquatic herb. The top 10cm of foliage can be emergent, standing above the water. Sprawling foliage is pale grey-green and stems are up to 2m long. Leaves are finely divided, feathery, and arranged in whorls of 4 -6. Emergent and submerged leaves differ in form. It flowers from September – February. Only female plants are present in New Zealand so no seed is set.

All nodes are capable of rooting, allowing the plant to form dense mats in still or slow-moving water, or on damp ground. It thrives in water with high nutrient and sediment levels—particularly peat—and can tolerate pollution. The plant is also resilient to damage, grazing, temperature extremes (both hot and cold), and low levels of salinity. It will be found in still or slow-moving water bodies including wetlands, lakes, streams, rivers, drains and ponds to a depth of approximately 5m+. Growth rates increase in response to increases in carbon dioxide, and the plant may benefit from climate change.

Why is it a problem?

This plant has a history of invasiveness overseas. Within catchments, it’s spread by flowing water, and new catchments are infested by fragments spread by boats and trailers, eel nets, diggers, and people 'liberating' fish. Birds are unlikely to spread it.

It forms dense mats, shading out existing native species and preventing new seedlings of native species from establishing, and replaces species that usually grow on the margins of waterbodies. Large clumps dislodge, causing flooding, and rotting vegetation stagnates water, killing fauna and flora.

Control methods

Physical control
Rake up from November to January and leave on site to rot down. Make sure it’s away from water and then follow up from February to April by spraying any regrowth. Or,
Weedmat: Lay carefully to ensure fragments are not released. Start at top of infestation and leave for 3 to 4 months.
At lower water levels, mechanically remove and use a weedmat to cover the area or dry out thoroughly for 2 to 3 weeks.

Herbicide control
Spray terrestrial sites (spring-autumn) using glyphosate (20ml/L + penetrant). Spray 4 times over a 10 week + programme.
Before you carry out any control work, make sure the plant you are targeting is not a valued native species. Plant trees adjacent to narrow waterbodies to create shade, create riparian strips, and remove pollution sources to prevent nutrient runoff.

CAUTION: When using any herbicide or pesticide, PLEASE READ THE LABEL THOROUGHLY to ensure that all instructions and safety requirements are followed.

Related links

• Check Clean Dry
• Freshwater Invasive Species Guide 2020
• Ministry for Primary Industries
• New Zealand Plant Conservation Network
• NZ Flora
• NZ Freshwater Weed and Pest Visual Guide
• Unwanted Organisms Register
• Weedbusters
• NPPA and the control of weeds | NZ Government