Floating pennywort: Environmental control (e.g. shading, reduced flow, reduction of rooting depth, or dredging)
Overall effectiveness category Awaiting assessment
Number of studies: 0
Background information and definitions
There are several possible methods of environmental control of floating pennywort Hydrocotyle ranunculoides, none of which give a complete solution.
Shade may be an effective method of control as the plant does not establish well in shaded conditions, and may be achieved by planting trees on the south side of the water body (Newman & Duenas 2010). This is unlikely to be practical to implement on larger water bodies.
Increasing flow will restrict the growth of floating pennywort in situ but may increase the spread of the plant downstream (Newman & Duenas 2010).
Increasing rooting depth to below one metre may reduce the ability of floating pennywort to root at the margins (Newman & Duenas 2010). This, however, will not often be a feasible option. Reducing the amount of suitable rooting substrate by piling or preventing access to suitable areas by netting off sections may prove effective (Newman & Duenas 2010).
All these environmental options are likely to be expensive to implement and are untested (Newman & Duenas 2010).
It is reported that dredging does not seem to be an effective method to eradicate floating pennywort (Haury et al. 2010). It is also reported that survivorship of floating pennywort may be prevented by a rise in salinity (Ruiz-Avila & Klemm 1996)
Haury, J., Hudin, S., Matrat, R. & Anras, L. (2010) Manuel de gestion des plantes exotiques envahissant les milieux aquatiques et les berges du bassin Loire-Bretagne. Fédération des conservatoires d'espaces naturels, Loire-Bretagne. 136 pp.
Newman J.R. & Duenas M.A. (2010) Information sheet: control of floating pennywort (Hydrocotyle ranunculoides). Centre for Ecology & Hydrology, Wallingford, UK. 3pp.
Ruiz-Avila R.J. & Klemm V.V. (1996) Management of Hydrocotyle ranunculoides L.f., an aquatic invasive weed of urban waterways in Western Australia. Hydrobiologia, 340, 187-190.