Water-crowfoots
What are they?
These attractive plants are essentially white-flowered buttercups and are plaved in the same genus (Ranunculus) though as a separate subgenus (Batracium) of that large group of plants. They share many of the characteristics of buttercups, including five petals and multiple stamens and carpels in the centre of the flowers.
Where are they found?
Water-crowfoots are plants of watery or muddy places. Some species may be found in great quantity in permanent running water in chalk streams, while others favour the still water of ponds or their muddy margins.
Identification
Although recognising a water-crowfoot is easy, putting a name to species can be difficult because there is much variation in the appearance of the plants according to their growing conditions. It is important to note the following features: the shape of the nectar pit on the yellow base of the petal; presence or absence of either broad, floating leaves and/or finely-cut submerged leaves; hairiness of the green carpels in the centre of the flower (these swell to become the fruits); sepal detail. Note that the nectar pit is a small area at the base of each petal that produces a small blob of nectar to attract pollinating insects. This pit has a raised edge which can be seen with a x10 hand lens and the raised edge may be either semi-circular, circular or narrowed at one end and somewhat pear-shaped.
Ivy-leaved Crowfoot Ranunculus hederaceus
Native. Scarce and declining and scattered at a few sites across Norfolk, but mostly more or less coastal in Suffolk. Typically found growing on muddy banks of ponds or slow-moving rivers rather than in the water. Flowers mostly late May to August. Leaves three-lobed, but not deeply so and rather resembling ivy leaves. Petals well-spaced (not overlapping), with semi-circular nectar pit. Sepals not reflexed, carpels and fruits hairless.
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Brackish Water-crowfoot Ranunculus baudotii
Native. Frequent in coastal wetlands where there is saltwater influence and most often found in ditches and ponds on grazing marshes - further inland on salt-influenced areas in the Fens and Broads. Usually growing in water but will survive on wet mud where ponds dry out in summer. Flowers mostly late May to August. Plants may have both broad, floating leaves and deeply cut, submerged leaves, or may have only submerged leaves. Floating leaves are divided more than half way into usually three lobes; submerged leaves stiff with segments strongly divergent. Flowers with reflexed, bluish-tinged sepals; petals with semi-circular nectar pit. Immature fruits hairless, the fruiting body becoming taller and more oval than other species as the fruits mature.
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Common Water-crowfoot Ranunculus aquatilis
Native. Scattered throughout the region in ponds and ditches on usually chalk-influenced, still or slow-moving waterways. Despite the name, not particularly common. Flowers mostly late May to August. Floating leaves broadly three- or five-lobed, the lobes cut about half way into the leaf and only narrowly diverging at the leaf base; submerged leaves with stiff and strongly divergent segments. Petals rather broad and with circular nectar pit. Sepals not reflexed, carpels and fruits downy.
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Pond Water-crowfoot Ranunculus peltatus
Native. Uncommon and perhaps declining due to habitat loss. Typically found in ponds, ditches or slow-moving rivers. Flowers mostly late May to August. Floating leaves broadly three- or five-lobed, the lobes usually cut a little more than half way into the leaf and usually strongly diverging at the leaf base; submerged leaves with stiff and strongly divergent segments. Petals rather broad and with pear-shaped nectar pit. Sepals not reflexed, carpels and fruits downy.
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River Water-crowfoot Ranunculus fluitans
Native. A species of faster-flowing chalk streams and rivers, mostly confined to the west of our region. Flowers mostly late May to August. A perennial species, rooted on the river bottom with stems and leaves trailing in long horsetails in the current. Leaves all submerged, with long, thread-like segments, the leaves longer than the stem internodes. Petals broad, with pear-shaped nectar pit. Sepals not reflexed, carpels and fruits variably downy to hairless, receptacle hairless.
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Fan-leaved Water-crowfoot Ranunculus circinatus
Native. A perennial of often deeper waterways such as gravel pits, lakes and deeper, slower-moving rivers. Flowers mostly late May to August. Leaves all submerged, their segments finely-dissected and lying in a single, fan-shaped plane. Petals well-spaced (usually barely touching when fully open), with semi-circular nectar pit. Sepals not reflexed, carpels and fruits hairy.
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