Llanelli Naturalists Newsletter - March 1985
George Hutchinson

Have you ever seen those white petalled buttercups with yellow centres floating in streams, rivers, ponds, lakes and in wet meadows on mud, particularly in May, June and July? These are the Water Crowfoot or Water Buttercup, members of the genus Ranunculus as are all Buttercups, but split off into a subgenus of their own called Batrachium.

Being look-alikes they tend to ha ignored by the average nature lover with such phrases as “Oh, that’s a Water Crowfoot, I don’t know which one though, they’re to too difficult to identify.

My interest in them started when I noticed the stream which flowed through my village was choked with one of them throughout the year, culminating in a mass of delicate flowers in late June and early July.

A look at the usual botanical guides including the good illustrations on Plato 2 of Keble Martin’s “Concise British Flora in Colour” did not convince me of its identity. “British Water Plants” by Sylvia Haslam et. al. indicated it could be Ranunculus penicillatus variety calcareus. It was a case of “taking the bull by the horns” and sending some pressed material to the Referee for the Batrachium in the U.K., Dr. Nigel T.H. Holmes, Nature Conservancy Council, P.O. Box 6, Huntingdon PE18 6BV, who confirmed my identification and referred me to “A Guide to Identification of Batrachium ranunculus Species in Britain” which offers the best guide to Water Crowfoots in Britain.

The advantage is that it contains a lateral/tabular key which allows the maximum number of relevant identifying features to be compared simultaneously, In Carmarthenshire the most commonly encountered species by far are Ranunculus omniophyllus and Ranunculus hederaceus. They happen to be the only British species with pat entire leaves. Growing on mud and in shallow water in disturbed habitats, they have no need to produce the thread-like divided leaves of ether species. Bare mud on the edges of streams and mud churned up by cattle’s hooves are favourite sites for colonisation. Ranunculus omniophyllus prefers mere acid environments and is thus probably more common in Carmarthenshire in my experience; Ranunculus hederaceus preferring more basic conditions the commoner species of the coastal lowlands, although there is a wide overlap and the 2 species can be seen growing together at times. They offer the first challenge of identification for the Batrachium spotter and can be separated by leaves alone.

Ranunculus omniophyllus - Leaf lobes (segments) narrowest towards their base, i.e. towards the centre of the leaf. Broadest part of lobes towards the rim of the leaf. Petals 2 to 3 times longer than the pale green sepals underneath than which are often reflexed downwards.

Ranunculus hederaceus - Lobes broadest towards the centre of the leaf. Petals and sepals approximately the same length. Mature leaves often dark green in the centre resembling a miniature ivy leaf in shape and colour. Both species start flowering in spring, much earlier than most species.

Plants of different species of Batrachium may appear very similar while single species may exhibit a wide range of characters depending on environmental factors. One stands the best chance of separating species when they are in flower (mostly late June and July). This is either because flower parts are diagnostic, or because entire leaves only develop on certain species when they are in flower.

Here is an explanation of some of the terms one has to come to grips with when identifying Batrachium species:-

Entire leaves: These look like leaves, often lobed about ½ inch or less usually floating on the surface and are attached to the stem by their long petiole.

Divided leaves: These are not deeply dissected entire leaves but are submerged thin threads which can often be seen as large vegetative growths in rivers flowing gracefully with the current like a horse’s mane. These are the flaccid ones but some species have rigid ones which are often fan shaped. The rigidity of a species’ divided leaves is best checked at the site, ac the segments often clump together if specimens are taken for late examination and become limp.

Nectar pits: The upper surface of the petals are yellow at their base where they are attached to the rest of the plant. The nectar pits are found in the middle of this tiny area. Their shape is very useful for identification. Well camouflaged by colour, best seen with a hand lens. Look at well developed petals. Crescent-moon shaped (lunate) in trichophyllus, baudotii, triartitus and circinatus; circular in aquatilis; pear-shaped (pyriform) in flutans, penicillatus and peltatus.

Peduncle: The stalk of a flower. Attached to the stem at a node where there is usually an opposed leaf attached by its petiole. The relative length of leaves to the distance between nodes (internodes) is important.

Leaf length includes the length of the petiole.

Petal to Sepal Length ratio may be important.

Petals contiguous at anthesis - edges of adjacent petals overlapping then flower fully opened. To be used cautiously

Summary of Carmarthenshire Batrachium with divided leaves. Don’t forget the shape of the nectar pits for identification.

Ranunculus tripartitus. A semi terrestrial plant of shallow pools and temporary bodies of water. Coastal pools and one inland site in Carmarthenshire and decreasing over the British Isles. Flowers late March to April dying down by May and June when most other species start to flower. Divided leaves very fine flaccid; often absent. Peduncle in fruit equal to or less than petiole of opposite entire leaf. It is longer in the next species.

Ranunculus baudotii. Brackish pools and ditches near the sea, frequent on Burrows at Laugharne, Kidwelly and Pembrey. Also at Machynys and Pwll, Divided leaves rigid, yellow-green and always present. The individual seed heads (achenes) are characteristically winged (flat projections).

Ranunculus circinatus. Two sites near Kidwelly only one extant. A rare species in the

British Isles. Divided leaves, rigid and fan-like, in one plane. No entire leaves. The contiguous petals separate it from the next species.

Ranunculus trichophyllus. Ponds on Kidwelly Flats, Talley Lakes, Dinefwr Oxbows and in the

Upper Lliedi Reservoir. One needs flowers to separate from L. aquatilis.

Ranunculus aquatilis.    This aggregate comprises 3 species.

1. Ranunculus aquatilis. (sensu stricto). Widely distributed in the county but probably under-recorded. Can be confused with a few species; flowers essent¬ial. The only species with circular nectar pits. Entire leaves not always formed.
2. Ranunculus petatus. The species has a marked eastern distribution in South Wales, It has only been recorded in two squares west of Kidwelly and they are in Pembrokeshire. Prefers still water. Recorded from Bishops Pond, Talley Lakes, Taliaris Pool Dinefwr Park, Moat Farm Pond and Llyn-y-fan fach. Peduncle greater than opposed petiole of entire leaf when in fruit, separates it from aquatilis. Divided leaves rigid, separates it from the next species.
3. Ranunculus penicillatus. A common species in the county forming large vegetative growths of divide-leaves in rivers. This species has divided leaves - longer than the internodes on mature non-flowering shoots, separating it from peltatus. There are two varieties, both of which are recorded in the county, which can be distinguished from each other when the plants are in flower:

Var. penicillatus produces entire leaves, but only during flowering, which are absent in var. calcareus.

Var. calcareus is tolerant of slower flowing streams tending to occur in neutral or basic water, and never producing entire leaves. Streams flowing off the narrow carboniferous limestone band in the county would be a good place to look for this variety when in flower in late June and July. I have seen var. penicillatus in the Taf, Tywi and Teifi, and var. calcareus is recorded in the Gwendraeth fach and Loughor. Var. penicillatus prefers more acidic waters.

Var. vertumnus has clumpy round divided leaves occurring in fast flowing chalk streams. Not yet recorded from Wales.

Ranunculus fluitans. Recorded from the headwaters of the River Usk on the boundary of the county and occurring in large rivers like the Wye. With divided leaves only, which can be up to 20 inches in length and usually forked only up to four times, it is the giant of the water crowfoots.

So from the hills in the North-east, through the river systems, to the coastal pools, Carmarthenshire can boast all 10 species of British Water-crowfoot. I hope this introduction to the group will stimulate interest and help to clarify the taxonomy of this difficult group for readers.