Parrots Feateher on sale in an aquatic centre
Australian Swamp Stonecrop (Crasulla helmsii), water fern (Azolla filiculoides), reeds, rushes, sedges and algal blooms.
The alien invaders.
Parrots Feather is grown and widely sold by aquatic garden centres for domestic use. It has spread since the 1960s to over three hundred wild sites in the UK. It favours slow flowing water with a high nutrient status. It grows quickly, reproduces asexually and spread from stem fragments. Its bulk reduces water flow which, in turn, can raise the silt levels of pools and ponds. Cutting and clearing of this plant is not advised. It spreads through stem and root fragments which will then re-establish down stream. The best control is achieved through foliar applied herbicides, though this is specialist work that requires both an environmental risk assessment and consent from the Environment Agency. It is best to consult with an expert. Reducing nitrogen and phosphorous inputs will help manage the nutrient rich environment this plant needs. Remove its
Pool infested with Australian Swamp Stonecrop
food source and it will be less able to compete. This is the ideal long term solution.
Australian Swamp Stonecrop is an immigrant from Tasmania that arrived in the 1920s. It was sold as an oxygenating plant for ornamental ponds and was released to the wild. It spreads rapidly from fragments from cutting. Swamp Stonecrop grows to form very dense mats of vegetation that can engulf smaller ponds and pools, often choking them completely. It severely reduces the oxygen content of water and out competes all other indigenous plants, impoverishing the aquatic environment. Cutting and removing is not advised as it causes it to spread downstream. The most effective treatment is to use either root applied or foliar herbicides.
Water Fern is the only floating fern found in the UK. It is a native of North America. It floats on the water surface forming dense floating mats that shade out other plants and deoxygenate the water. It can cause serious problems to pumping and filtering equipment due to
Water Fern in winter
its size. In winter it turns a characteristic red colour. It is tiny and easily spread by contaminated water, or water birds. In times of stress it releases spores as a survival mechanism. There are many techniques to manage this floating pest. If possible, raising and then lowering water levels to leave it stranded on the bank is cheap and effective. If not, weed scoops will provide a short term solution, as will herbicides. Long term, increasing water flow, preventing it from gaining a foot hold, is the desirable option.
Native opportunists
In the right conditions native plants can establish and cause reductions in water flow and raise silt levels in pools, ponds and water storage lagoons. Sedges, reeds and rushes, when established, can quickly colonise new areas. They grow and spread via rhizomes that accumulate silt. This accumulation diverts water to other areas, often dropping the bankside water level making it shallow enough for other plants to colonise. This gradual process causes loss of capacity and the literal
Reaching New Heights
Osorno
A granular residual herbicide for the control of broad leaved
weeds, grasses and aquatic weeds. Osorno contains 6.75%w/w dichlobenil
Always read the label. Use pesticides safely. Osorno is a registered trademark of NuFarm Dispose of chemicals safely.
Sherriff Amenity The Pines Fordham Road Newmarket Suffolk CB8 7LG Tel. 01638 721888
www.sherriffamenity.com 59
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