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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.
Still or slow moving water bodies including wetlands, lakes, streams, rivers, drains and ponds to a depth of approximately 5+m. It is unlikely to be severely problematic in large exposed lakes. Tolerates slightly brackish conditions. Favours water bodies with high nutrient (especially nitrogen) and light levels. Tolerates fluctuating water levels, including complete exposure of sediment. Growth rates increase in response to increases in carbon dioxide. May benefit from climate change.
History of invasiveness overseas. Taller growing form than native Myriophyllum species. Rapid growth rate and highly variable growth forms. Allelopathic - releases chemicals that affect the growth of other species. Growth from fragments provides competitive advantage in dynamic environments.
Does not set seed in New Zealand. Grows from small fragments.
Freshwater weeds are difficult to eradicate once established, but are possible to control. Before you start thooughly check the waterway's adjacent areas and inflows to see if the infestation has spread.
As most aquatic weeds grow from fragments, start control at the upstream end of the infestation. In narrow waterways you can reduce the growth of aquatic weeds with riparian planting to reduce light levels.