• Floating pennywort (Hydrocotyle ranunculoides)

Floating pennywort (Hydrocotyle ranunculoides)

Floating Pennywort originated in North America and studies show that this invasion probably resulted from a single population made available through aquatic garden centres and nurseries. The plants form dense mats of floating vegetation on the water surface, altering the ecology of the water body.

This species is causing many problems,  "including deoxygenating the underlying water, killing fish and invertebrates, drowning cattle, choking drainage systems and sluices, causing extensive localised flooding, and crowding out our native plants such as Frogbit, Duckweed and Water Crowfoot” (English Nature, 1999)

Removal of floating pennywort can be achieved using a weed-cutting bucket or boat and must be repeated throughout the growing season due to its high growth rate. All loose fragments must be contained and removed from the water due to the plants' capability to spread from single fragments.

Chemical control is difficult for a number of reasons. The dense tangled growth restricts penetration of herbicide spray to underlying leaves, growing points may be below the waterline and subsequently protected, and the waxy cuticle of the leaves can restrict  herbicide uptake. The use of low volume, high concentration chemical should be adopted and treatment should take place early in the season (late June to early July).

Image Crown Copyright GBNNSS