Parrot's Feather Infestation
First found in the UK in the 1960’s Parrots feather is an alien invasive species. Parrots feather is native to central South America. It can now be found on up to 300 sites across the UK. While it has mostly been found in ponds, there have been instances of it living in gravel pits, reservoirs, canals, streams and ditches. Unlike other plants from the same genus, parrots feather has the ability to continue growing when ponds and waterways dry out. Its characteristic feathery appearance, producing both emergent shoots as well as submerged ones. The plant spreads by asexual means; this is because it is only the female plants that have established within the United Kingdom. The plants stems are quite brittle and the plant propagates itself through the growth of small fragments from the parent plants.
Unfortunately the species is sold by nurseries and aquatic garden centres and as a result is grown in ponds right across the UK. Garden centres also often sell M. propernaciodes, or M. brasiliense, or M. propium – these should be avoided as they are all also highly invasive species. Parrots feather has now become established in Austria and France, as well as the UK. It is not believed that the introduction of these plants has been deliberate, but that small fragments of the plant have been transferred via the soil of other purchased aquatic plants.
Mechanical control – Mechanical control via weed cutting boats is an effective method of removing large infestations of this plant. However, it is important that great care is taken to prevent any stem fragments (the stems are very brittle and fragmentation happens easily) from floating downstream as their regrowth is rapid.
Chemical control – The plant can be controlled by applications of glyphosate late in the season, and also to some extent by applications from April onwards. Short term elimination of parrots feather can occur with chemical control, however recolonisation from original sources will often take place. Because of this it is important to try to eliminate the infestation at the source.
Biological control – Grass carp will not eat this species unless they are at least 2 years of age and then only reluctantly if no other preferred species are present.