Parrots Feather

Also known as:
Parrot's Feather
South America

General description

Stout, hairless, freshwater perennial. Sprawling mats in water or carpets of short growth on semi-exposed banks. Submerged stems yellow-green, emerge 10cm above water. Stems <2m in still water and <4m in flowing water; fibrous roots at each node. Emergent leaves in whorls 4-6, densely packed at stem ends, bright blue-green, deeply divided, feathery. Small single flowers have no petals.

Still or flowing freshwater, rooting either above or <2m below water surface. Prefers nitrogen-rich water, temperatures 8-30ºC; tolerates occasional frosts, some salinity.

No seed set in NZ. Spread by stem fragments carried by water, boats, fishing gear, machinery.

Traps sediment, infills shallow waterways, impedes drainage, causes flooding, disrupts recreational activities, out-competes native water plants.

Site management

Very difficult to control in deep water. Stem fragments resprout. In narrow waterbodies, reduce light levels with riparian planting.

Recommended approaches

1. Rake up and dispose, follow up. Spray marginal regrowth.
2. Weed mat small areas, 3-4 months. Start at top of infestation.
3. Lower water level, mechanically remove, use weedmat or dry out thoroughly for 2-3 weeks.
4. Suction removal generally not recommended in large still waterbodies, high chance of fragments spreading. If used, trap all fragments. In moving water all sites below top of infestation are at risk.
5. Spray emergent vegetation including banks <500mm above present water level Oct- Nov (100ml glyphosate/10L, use glyphosate formulation approved for use over water). Respray before growth reaches 50mm high, approximately 3-5 weeks apart. Respray Jan-Feb. Monthly checks over winter to pick up regrowth.

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

Similar species

Ceratophyllum demersum

Hornwort has forked leaves as opposed to the pinnate leaves of parrot's feather.

Eurasian water milfoil
Myriophyllum spicatum

Parrot's feather has less than 12 leaflet pairs per leaf in comparison to E. water milfoil which usually has greater than 12.

Myriophyllum robustum

Native milfoil is monoecious (males and females on the same plant), the exposed stems are usually pink coloured and the leaf tips which are acute rather than blunt ended.

RPMS status

Surveillance - Whole Region
National Pest Plant Accord species - nationwide
parrots feather - Main species image