Scientific name Apium nodiflorum – Ranunculus penicillatus aquatic community
Common name Fool’s-water-cress – Stream Water-crowfoot aquatic community
Community code FW2D


FW2D map: Apium nodiflorum – Ranunculus penicillatus aquatic community

Download full pdf synopsis: FW2D



This aquatic community has a notable floating-leaf component, with Ranunculus penicillatus (subsp. penicillatus) a constant species, as is Fontinalis antipyretica. The curly leaves of Potamogeton crispus are also frequent here, whilst other pondweeds (Potamogeton natans, Potamogeton pectinatus, Potamogeton lucens, Potamogeton pusillus and Potamogeton perfoliatus) may all occur but are individually rare. The main free-floating plant is Callitriche stagnalis, a constant, with Lemna minor and Lemna trisulca both occasional. Submergents consist of Zannichellia palustris and Myriophyllum spicatum. There is also a significant marginal/emergent component where Apium nodiflorum is constant, frequently accompanied by Berula erecta, Rorippa nasturtium-aquaticum agg., Phalaris arundinacea, Mentha aquatica and Glyceria notata. Leptodictyum riparium and Rhynchostegium riparioides provide a bryophyte element to the assemblage.



This vegetation occurs in fairly eutrophic, base-rich rivers and streams.



No sub-communities are currently described.


Similar communities

Ranunculus penicillatus and Fontinalis antipyretica are also constant features in the FW2C aquatic community. That community, however, has a less pronounced emergent and marginal element with both Apium nodiflorum and Berula erecta less frequent. Furthermore, Callitriche stagnalis is seldom encountered in FW2C. From FW2E, the present community differs by the higher frequency of pondweeds and the lower dominance of Rorippa nasturtium-aquaticum agg.


Conservation value

Almost all examples of this community with a relative abundance of crowfoots (Ranunculus spp. subgenus Batrachion) correspond with the EU HD Annex I habitat 3260 Floating river vegetation. Elodea canadensis is a non-native submergent that is not considered a major ecological threat and has already colonised much of its suitable niche in Ireland.



This community has no specific management. Eutrophication from discharges and agriculture run-off is probably the major threat. Other impacts may come from river engineering and trampling from livestock with access to the bankside.