|
Beware of invasive aquatic species By Andy McConnachie from Aqua Landscape Design
Where possible, use native plants in your pond to help fight the threat of invasive species which can drain goodness and energy out of the water
Japanese knotweed for example is widely considered to be the UK’s most damaging non-native plant. However many people may not be aware of the scale and impact of invasive species found within ponds. By definition an invasive species is described as any introduced species that can out compete a native species for space and nutrients. Introduction is usually intentional as many invasives can be visually impressive; unfortunately often little or no thought is given to the long-term implications of the introduction. An attractive non-native species may seem to add colour and exoticism to a UK pond but the invasive may quickly spread and out compete native species, so that the pond can quickly turn to a monoculture only able to sustain the non-native. Once popular pond plants like parrots feather, Myriophyllum aquaticum, water lettuce, Pistia stratiotes and floating pennywort, Hydrocotyle ranunculuoides are now causing major problems to our natural lakes, streams, canals and other water ways. Floating pennywort, often considered to be one of the most damaging invasives, was first found in the wild in 1990 in still or slow-flowing water bodies. It can grow up to 20cm a day, rapidly clogging up the surface, blocking out light and reducing oxygen for other aquatic inhabitants. It has been known to block drainage ditches and storm channels, increasing the potential risk of flooding. The plant is able to regenerate from the smallest of fragments, making it almost impossible to completely eradicate from an infected area. It is suspected that the initial plant came from a garden pond owner unaware of the potential damage a non-native species could cause. The outbreak has lead to a firm stance being taken from authorities and any action resulting in the spread of pennywort can result in prosecution. There are a number of simple steps pond owners can take to help protect our natural aquatic environments from further damage by invasive species. Firstly and most importantly know what you are buying. A reputable retailer should have a detailed knowledge and understanding of all aquatic plants. Don’t be afraid to ask questions and always ask if the aquatics plants available for sale are permitted under UK legislation. Although you can no longer buy American Floating Pennywort some suppliers and stockists are now selling the New Zealand variety, Hydrocotyle nova zealandiae, which has caused problems in other parts of the world. Plants like Parrot Feature, an attractive oxygenator, is still available from stockists and although it is not illegal to sell or buy this plant it is an offence to plant or otherwise cause this plant to grow in the wild. If in any doubt contact a reputable retailer or visit the government-run ‘Be plant wise’ campaigns website at; www. beplantwise.direct.gov.uk. At Aqua Landscape Design we make sure that we only stock plants we know will not cause harm to the natural environment and offer help, advice and identification for most problem species. We are also able to do large-scale aquatic weed control for commercial and residential clients. The plants in your pond will need to be managed regularly as they can become overgrown and if left to spread can lead to many detrimental conditions within the pond. Make sure all plant matter is composted and that any water from your pond is poured over the garden rather than down the drain or into water ways. Avoid getting plants from other ponds as many non-invasive species carry small plant fragments from invasive species that can spread quickly, for example Azolla, Azolla spp or New Zealand Pigmy weed, Crassula helmsii, can rapidly regenerate and smother your garden pond. Where possible, use native plants. Plants like oxygenator Hornwart, Ceratophyllum demersum, or the floating plant Frogbit, Hydrocharis morsus-ranae. These plants are not only perfectly suited to the conditions found within our ponds but can be an attractive and beneficial addition.
|
