Floating Pennywort

(Hydrocotyle ranunculoides)

Floating pennywort Hydrocotyle ranunculoides (hereafter H. ranunculoides) is a non-native and invasive aquatic plant originating from North America. It is not to be confused with the native Marsh Pennywort Hydrocotyl vulgaris. . H. ranunculoides roots in the shallow margins of lakes and lowland rivers. The species can grow up to 20cm per day and spreads rapidly within a waterbody, forming thick mats of vegetation on the surface which can impede water flows and amenity usage. The plant is able to regrow from small fragments, making transmission to new water bodies very easy and complete removal from a system very difficult. Floating pennywort is particularly problematic on small rivers and streams. Under the right conditions, the plant can significantly reduce light penetration through the water and reduce oxygen levels.  H. ranunculoides invasions can also reduce river flows, increasing sedimentation which may have flood risk implications. Invasive pennywort should be managed with care and with the support of a qualified individual. Chemical treatment is considered the most effective method of H. ranunculoides removal but this should be approached with caution, to avoid water pollution with herbicides. More information on H. ranunculoides can be found at the links below.

Invasive weed control

Control of Floating Pennywort

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