Ranunculus sceleratus L., Celery-leaved Buttercup

Account Summary

Growth form and habitat preferences

R. sceleratus is quite a tall (30-70 cm), conspicuous but rather scarce, much branched, yellowish green plant producing a host of rather small yellow flowers. This many-seeded winter or summer annual is a pioneer coloniser of shallow water, or wet, disturbed, nutrient-rich (especially nitrogen-rich), bare mud after it has been thoroughly disturbed, eg heavily trampled and poached by drinking livestock. The animals also provide, of course, the required nitrogen in their excretion (van der Toorn 1980; R.A. Fitzgerald, in: Preston et al. 2002). The wet, open, almost always lowland habitats it frequents are generally flooded and deeply submerged for part of the winter months and often indeed remain so into the late spring or even the summer in our wet Oceanic (or Atlantic) climate. R. sceleratus is totally absent from soils below about pH 4.0 and it never occurs in permanently flooded aquatic sites (Grime et al. 1988).

With regard to its ecological status, R. sceleratus is always a pioneer species colonising bare mud. Among its many associates are Myosotis scorpioides (Water Forget-me-not), Rorippa palustris (Marsh Yellow-cress), Persicaria hydropiper (Water-pepper), Alisma plantago-aquatica (Water-plantain), Veronica beccabunga (Brooklime), Lemna minor (Common Duckweed), L. trisulca (Ivy-leaved Duckweed), Callitriche stagnalis (Common Water-starwort) and Bidens cernua (Nodding Bur-marigold). In terms of plant communities, R. sceleratus belongs chiefly to the NVC OV32 Myosotis scorpioides-Ranunculus sceleratus open, nitrogen-rich, often muddy and disturbed, intermittently wet ground community (Rodwell et al. 2000, page 434), an Association of the Bidention Alliance which goes under various names in different parts of W Europe (White & Doyle 1982). It does also occur however, as a regular associate in seven other aquatic and swamp communities listed in Rodwell et al. (1995).

Like most pioneer colonisers of bare ground habitats, the presence of R. sceleratus tends to be ephemeral. Where disturbance occurs more rarely or irregularly, it is gradually crowded out by the arrival of taller, more permanent colonising vegetation dominated by species such as Phragmites australis (Common Reed), Typha latifolia (Bulrush), Schoenoplectus lacustris (Common Club-rush), Equisetum fluviatile (Water Horsetail), Cicuta virosa (Cowbane) and Iris pseudacorus (Yellow Flag). The latter, together with various sedges and a collection of other invading and carpeting species, can very quickly cover and occupy previously bare mud, out-competing and excluding R. sceleratus. In addition, should the inhabited site dry out during a prolonged drought, R. sceleratus quickly succumbs. It is too fleshy and succulent to survive dry conditions for long (Grime et al. 1988).

Fermanagh occurrence

This is a rather scarce annual which had only been seen twice in Fermanagh before 1980, but since then it has been recorded at 15 new sites covering 21 tetrads, 4% of the total in the VC. As the distribution map shows, it is thinly scattered in seasonally flooded water meadows around the Upper Lough Erne basin, mainly in the south of the county, with one outlying station at Derryclawan near Enniskillen. The latter is the only station where it was found in any real quantity and here it grows on cattle poached, wet, well-dunged, anaerobic or very poorly-aerated mud on the bed of an old lake exposed in summer after a spell of dry weather.

Flowering

R. sceleratus flowers are remarkable for their outsized, elongated, pineapple-shaped receptacle, which sits quite incongruously amongst the encircling small petals and tends to dwarf them. Flowers are produced mainly from May to September, but chiefly from June to August. They attract flies and bees with freely presented nectar and they may be cross-pollinated by wind or by their winged insect visitors (Clapham et al. 1962; van der Toorn 1980). In addition, if this fails to occur, the travels of thrips and aphids crawling around individual plants enables self-pollination (Baker & Cruden 1991).

Seed production

The many seeds of the plant (ie the achenes − single seeded dry fruits), are produced at rates of between 70-100 per receptacle and up to 45,000 per plant (with a mean of 26,000, however) (Salisbury 1942). Another estimate given by van der Toorn (1980) indicated that a large plant in very good growing conditions and with little or no competition can produce up to 50,000 achenes. The individual seeds/achenes are smaller than those of R. flammula (Lesser Spearwort) and many times smaller than those of R. lingua (Greater Spearwort) (Clapham et al. 1962).

Seed dispersal

Seed dispersal involves wind and water. Seeds float for at least an hour, but generally somewhat longer, the distance travelled obviously dependent upon rate of water flow and density of waterside vegetation (van der Toorn 1980).

Germination and life-cycle/growth strategy

Celery-leaved Buttercup seed which has been stratified by winter cold for 4 to 6 months and subsequently exposed will germinate in the spring or early summer (van den Toorn & ten Hove 1982). The species can complete its life-cycle in two months (ie behaving as a summer annual). If it germinates later in the summer, for instance in August or September, it is frost resistant and may persist through the winter as a submerged dormant leaf rosette. It then recommences growth when the mud it occupies is exposed the following year − ie it behaves as a winter annual, thus giving the species a dual life strategy (Bakker 1966; van der Toorn 1980). During the second year, these winter annuals will probably seed early in the summer and, since a proportion of the fresh seed can germinate immediately, there may be sufficient time for a second generation to grow and complete their life-cycle in the same season (Bakker 1966; Grime et al. 1988).

In the first year or so after germination, R. scleratus can build up its population very quickly due to its enormous seed output and their easily achieved dispersal by wind and water.

Buried seed survival

Despite their small size, the seeds can lie dormant and survive for many years on the muddy margins of lakes, ponds and ditches, until low water levels expose the bare mud and disturbance brings them up to the light, triggering germination. Five of the 13 records quoted in the survey of NW European soil seed banks reckoned that R. sceleratus seed is long-persistent: one estimate reckoned survival is possible for over 50 years (Thompson et al. 1997).

British and Irish occurrence

In suitable muddy habitats in other parts of Northern Ireland, Celery-leaved Buttercup is much more common than it is in Fermanagh, eg in Co Down (H38) and in all the vice-counties around Lough Neagh in particular, ie Cos Tyrone, Armagh, Down, Antrim and Londonderry (H36-H40) (Harron 1986). It is also more frequently found in coastal areas both around the province and in the wider British Isles. R. sceleratus is tolerant of brackish alluvial mud conditions and therefore it is also a frequent pioneer coloniser of mud on grazed or otherwise disturbed estuarine saltmarshes (NI Flora Website 2002; R.A. Fitzgerald, in: Preston et al. 2002). Overall, however, R. sceleratus occupies a rather restricted niche habitat and it is not surprising that although it is widespread and frequent in C & SE England, the species is uncommon in many inland parts of Ireland, Wales and Scotland (Gray 1970; Stace 1997).

European and world occurrence

In Europe, R. scleratus is widespread, especially in C & W areas, becoming scattered to rare and increasingly coastal to both the north and south of its range (Jalas & Suominen 1989, Map 1828). The species extends through the Near East, Siberia, C Asia, Japan to eastern N America (where it is in fact also represented by an additional subspecies, subsp. multifidus) (Hultén 1971, Map 291). A further subspecies, subsp. reptabundus (Rupr.) Hult. is later mapped in N Europe and NW Siberia (Hultén & Fries 1986, Map 857). Hultén remarks that as the plant is so often apophytic (ie occupies man-made or strongly man-influenced habitats) it is difficult to decide exactly where R. sceleratus is native. He is particularly suspicious about its native credentials in eastern N America, and I would go further and say that it is always introduced in N America. In the southern hemisphere, Celery-leaved Buttercup is a certain introduction, for instance, in C & E Africa, New Zealand, Queensland and Tasmania (Hultén 1971; Jonsell et al. 2001).

Fossil record

Living as it does in nutrient- and nitrogen-rich muddy habitats and requiring disturbance to initiate germination, R. sceleratus is very often associated with human settlements. This naturally raises the possibility that in some places it might be an ancient introduction, ie an archeophyte. However, these muddy habitats also favour preservation of fossil pollen and achenes and this evidence clearly indicates that R. sceleratus has been continuously present in Britain and Ireland from the Pastonian stage onwards. Thus Celery-leaved Buttercup is very definitely a native species (Godwin 1975).

Toxicity

Like other buttercups R. sceleratus contains the glycoside ranunculin, which on hydrolysis breaks down to yield an irritant oily substance protoanemonin, plus glucose (Saber et al. 1968). Protoanemonin is responsible for the toxicity of all Ranunculus species, and R. sceleratus is reputed to be the most poisonous of all. It is possible, however, that because of the rich, luxuriant, somewhat succulent growth of the plant, it may be eaten in larger quantities than other buttercup species. Protoanemonin poisoning is reported most frequently in cattle, the acrid juice causing blistering of the mouth. In an experimental trial, one goat fed with R. sceleratus died and two others became severely ill. Celery-leaved Buttercup does not normally invade pastures, but a horse that grazed an area where it had access to R. acris (Meadow Buttercup) and R. sceleratus temporarily developed paralysis, convulsions and a loss of sight and hearing (Cooper & Johnson 1998).

Names

The plant's toxicity undoubtedly explains why it was given its Latin specific epithet 'sceleratus', which means 'wicked' or 'vicious' (Gilbert-Carter 1964).

Apart from the aptly descriptive English common names, 'Celery-leaved Buttercup' and 'Celery-leaved Crowfoot', the plant is also known in N America as 'Cursed Crowfoot'. Presumably farmers whose animals attempt to eat it, refer to it in this way. An alternative common name listed by Britten & Holland (1886) is 'Ache', apparently through a connection with the old French name for Parsley, and thus a connection via 'Apium' to the vegetable, Celery. A further name 'Thiretelle' originates in two dictionaries of obsolete English which refer to, "The herb apium risus", which is identified by Britten & Holland (1886) as R. sceleratus. Another name these authors mention is 'Blisterwort', which originated with Lyte (1578), and is a useful reminder that buttercup sap very readily causes burn-like blisters on skin.

Uses

In past times, beggars were said to use buttercup species commonly, and especially R. sceleratus, in order to induce sores on themselves to excite compassion and gain alms from the public (Lightfoot 1777, p. 291; Vickery 1995, p. 63). According to Mrs Grieve who reports this nefarious use of the plant, after 'working' their 'con', the beggars afterwards would cure their blisters by applying fresh Mullein leaves to the wounds (Grieve 1931, pp. 182 & 235). Funnily enough, Grieve does not mention this healing property under her entry for Mullein (Verbascum species). Poor beggars! Grieve warns that R. sceleratus, "is one of the most virulent of native plants: bruised and applied to the skin, it raises a blister and creates a sore by no means easy to heal". She goes on to indicate that if the plant is boiled and the water discarded, it can be eaten as a vegetable, and was peasant food in Wallachia (an old name for Romania). Grieve mentions a tincture, used in small doses, as an herbal cure for "a stitch in the side and neuralgic pains between the ribs".

R. sceleratus is widely used to this day in homeopathy and numerous internet websites deal with this topic. YOU ARE STRONGLY ADVISED NOT TO MAKE ANY ATTEMPT TO MAKE USE OF THIS VERY DANGEROUS CAUSTIC PLANT.

Threats

Due to the general nutrient enrichment of aquatic habitats, we may see this species increasing, provided that climatic change does not reduce the water level fluctuation that provides bare mud for colonisation.

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