Habitat: stagnant and slow flowing freshwater systems.
Description: Fanwort is fully submerged except for occasional floating leaves and emergent flowers. The roots grow on the bottom of water bodies and the stems can reach the surface. It is a perennial, growing from short rhizomes with fibrous roots. The branched stems can grow up to 10m long and are scattered with white or reddish-brown hairs. The underwater leaves are divided into fine branches, resulting in a feathery fan-like appearance. These leaves are about 5cm across and secrete a gelatinous mucous which covers the submerged parts of the plant. The floating leaves, however, are small, diamond-shaped, entire, and borne on the flowering branches. The solitary flowers are less than 2cm across and range in colour from white to pale yellow and may also include a pink or purplish tinge. The flowers emerge on stalks from the tips of the stems.
Origin and Distribution: Native to South America and also some southern states of the US. The species is currently invasive in North America, Australasia-Pacific, Australia and Asia. The species has also been recorded on sale in Britain.
Impacts: This species can form dense stands that crowd out well-established plants. Fanwort spreads primarily by stem fragments making control difficult if not impossible in some circumstance. Where infestation rates are high, waterways can become clogged with ecological, recreational and economic consequences. Drinking water can also become tainted by this species adding additional costs to treatment.
How might it get here? This is a popular aquarium plant. Transport and inappropriate disposal of this plant is considered the most likely route into Ireland
GB Risk Assessment EU Risk Assessment
- Promote native species and biodiversity - use alternative, native plants
- Know what you are buying/growing and source native Irish seed and plants
- Do not swap plants and cuttings
- Clean plants before adding to ponds (dispose of water away from water courses)
- Follow control advice and watch out for hitchhikers - inspect new imported purchases for invasive pest and pathogens
- Clean equipment before moving between waterbodies
- Never collect plants from the wild.
- Safe disposal of plant material and growing media.