The blooms of water-crowfoot, a helpful aquatic plant, brighten streams and rivers in early summer
How to identify water-crowfoot
Like blackthorn blossom that has fallen into a clear stream, water-crowfoot brings a smile to the water. In May and June, the crystalline purity of England’s chalk streams lights up with the five white petals of this aquatic member of the buttercup family, the display draping over the long ropey filaments of the submerged plant.
Why is water-crowfoot a sign of a healthy river?
Far more than just a pretty sight, water-crowfoot is a barometer that allows us to gauge the health and cleanliness of the stream. The plant is also a surprising habitat that supports a rich collection of life, from freshwater shrimps to Atlantic salmon.
Water-crowfoot has a family network as tangled as its stems. In Britain, many different species occur, which are difficult even for experts to distinguish. But regardless of which species is in a riverbed, water-crowfoot functions like fingers in the waterflow, sediment catching on its feathery fronds. As you look from the bank upon its long green strands, it is easy to imagine the nymphs and larvae sheltering there.
Fish soon follow. River-keepers have long tended water-crowfoot, but science provides a startling view of this plant from a salmon or trout’s perspective. Research on the River Frome in Dorset shows that not only do young fish congregate around it – giving protection from predators and extreme temperatures – but they grow faster and better, increasing their chances of survival when they migrate to sea.
Is water-crowfoot under threat?
Like all buttercups, water-crowfoot has a sinister side; it contains a compound called ranunculin, which is poisonous to many mammals if eaten. Nevertheless, water-crowfoot is foraged by swans and ducks, which has caused concern on occasion when grazing pressure is severe. Low water levels from abstraction are also a risk to the plant, as is nutrient enrichment. When inputs such as phosphates are washed off farmland or leak from sewage effluent, water-crowfoot tends to decline and algae blooms instead.
Where to see water-crowfoot
Water-crowfoot is by no means limited to chalk streams – its pretty white flowers adorn many larger and slower watercourses. But the chalk remains its most poetic home. These chalk streams are one of our special habitats; England hosts over three quarters of the world’s total.
Listen to our award-winning podocast, The Plodcast, when we explored the amazing life of a Hampshire chalk stream with insect expert, Dr George McGavin.
Find out more
Check out our expert guides, including how to identify freshwater pond wildlife, garden pond guide: how to look after your pond and wildlife to spot, guide to small river fish: where to see and how to identify and guide to frogs and toads: when do they spawn and how to care for them.
