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Ranunculus lingua L., Greater Spearwort

Account Summary

Native, occasional, but easily overlooked and perhaps under-recorded. Eurosiberian temperate.

1836; Mackay, J.T.; Lough Erne.

May to September.

Growth form and habitat preferences

Greater Spearwort is an erect, robust, semi-aquatic, emergent perennial up to 120 cm tall with a creeping rhizome or stolon up to 50 cm long, bearing shallow fibrous roots (Jonsell et al. 2001). As such, it is a bigger plant that shares some of the characteristics of both R. flammula (Lesser Spearwort) and R. repens (Creeping Buttercup), ie like R. flammula it is a helophyte, growing in soil frequently saturated with water or it stands in shallow water with its base submerged. Again, like R. repens, the underground stoloniferous stem branches and produces offsets, daughter plantlets or ramets, which can play an important role in vegetative reproduction, clonal local diffusion and longer-distance dispersal of the species within a lowland, wetland system (Johansson & Nilsson 1993).

R. lingua is a plant of mesotrophic to eutrophic, rather nutrient-rich, sheltered, shallow water, rich-fen and swamp vegetation. It seems to prefer places where there is a fairly gentle inflow of stream water, presumably adding nutrients. It is often rooted in organic, peaty, lime- or base-rich mineral mud, usually with a pH between 5 and 6.5 (Spence 1964; Garrard & Streeter 1983; R.A. Fitzgerald, in: Preston et al. 2002). As is the case with R. auricomus (Goldilocks Buttercup) and some other species, which in the British Isles frequent calcareous or base-rich soils, in Nordic countries R. lingua appears indifferent to lime (Jonsell et al. 2001).

Fermanagh occurrence

Prior to 1975, there were a total of just 27 records for R. lingua in Fermanagh. However, thanks to the extensive recording in the VC from 1977 onwards, which has particularly focused on lowland wetlands, there are an additional 200 post-1975 records for Greater Spearwort in the Fermanagh Flora Database. This stoloniferous perennial has now been recorded in a total of 64 tetrads, 12.1% of those in the VC.

In Fermanagh, R. lingua grows among tall, often dense, fen and marsh reed vegetation, especially around the small inter-drumlin lakes that form the fretted margins of Upper Lough Erne. It is also found around a variety of other lakelets and ponds and on the muddy banks of rivers, canals and ditches, eg in marl ponds along the River Finn, on the banks of the Swanlinbar River, the Old Ulster Canal and in gravel-pits at Gortaree. It typically associates with Phragmites australis (Common Reed), Typha latifolia (Bulrush), Carex elata (Tufted-sedge), Equisetum fluviatile (Water Horsetail), Cicuta virosa (Cowbane) and Sium latifolium (Greater Water-parsnip). It is present, but not a constant or even a very frequent species in one aquatic (A4) and six swamp plant communities in the NVC listing (S1, S4, S17, S22, S24 and S27) Rodwell et al. 1995).

Although R. lingua is stoloniferous and potentially clonal patch-forming, in Fermanagh it is always a rather sparse and local component of the type of tall waterside vegetation it frequents. R. lingua is a decidedly inconspicuous plant until about mid-June when it comes into flower. It could thus be very easily overlooked during early season field recording. Seven Fermanagh tetrads contain only pre-1976 records, possibly indicating a loss of suitable habitat, or the need for more timely recording.

Greater Spearwort is said to be intolerant of trampling and grazing (Sinker et al. 1985), and since both these pressures must occur on the grazed water meadows along most of the Fermanagh lake shores where the species occurs, these two factors might well be limiting its local occurrence.

Flowering

R. lingua begins flowering in late June and continues until September, reaching a peak in July. The rather large, creamy yellow, very glossy- petalled flowers are usually borne in a few-flowered cyme, but sometimes flowers are solitary. The flowers are protogynous (ie their female stigmas ripen before their pollen) and they attract insect pollinators (mainly flies) by producing copious nectar (Clapham et al. 1962; Hutchinson 1972). Broad-leaved forms of R. flammula can easily be mistaken for R. lingua, but they have much smaller flowers, about half the diameter of those of Greater Spearwort.

Fruiting, overwintering and vegetative reproduction

R. lingua is described as 'thermophilous' by the Dutch botanists van der Voo & Westhoff (1961), meaning that it prefers relatively warm temperatures, or it requires such conditions to really thrive (Holmes 1979). Further north in Sweden, fruit-set is often poor and recruitment from seed is regarded as very infrequent. It is possible that from time-to-time in a poor summer fruiting may also be poor in parts of Britain and Ireland. I have not located any measurements or estimates of the reproductive seed capacity for this species in either Britain or Ireland and, clearly, there is need for further study in our latitudes. A Swedish study at around 60oN reported that individual plants (ie ramets) of R. lingua live for just one year, and that propagation occurs by means of overwintering rhizomes. These overwintering organs are up to 10 mm thick and 25-75 cm long and consist of 5-10 nodes. They are produced in late summer from basal stem nodes lying just below the sediment surface (Johansson & Nilsson 1993). This system of growth and perennation results in clones of physiologically independent ramets or daughter plantlets. It was observed that each established ramet went on to produce one or two daughter ramets each year of the study (Johansson & Nilsson 1993).

Dispersal

The overwintering rhizomes or stolons are very efficient water-borne dispersal units, being perfectly buoyant for long periods due to their having hollow internodes. In comparison, seed only floats for one to two hours, which must severely limit their efficiency as water-borne dispersal units (Romell 1938, cited in Johansson & Nilsson 1993). There is, however, a high mortality of dispersed ramets during the first year after dispersal, so that successful establishment, even from organs as large as rhizomes, must be rare events. In their study the Swedes concluded that (at least in their area) R. lingua is a "pseudo-annual clonal plant", and that annual clonal disintegration (of the individual plant) can be viewed as a form of (ecological and biological) risk-spreading (current author's inserted brackets) (Johansson & Nilsson 1993). The probability of extinction decreases because some ramets are always devoted to dispersal to new sites. "In reality, however, only a few of all rhizomes are dispersed, and this can also be interpreted as a safeguard against local population extinction." (Johansson & Nilsson 1993).

Although seeds in many wetland species are ineffective for long-distance dispersal within water systems, their smaller size and longer life must still allow them to be the most effective means of dispersal between water systems by transporting agents such as birds and other animals (Smits et al. 1989). Only one reference is given in the comprehensive survey of soil seed banks of NW Europe (Thompson et al. 1997), and it suggests that seed of R. lingua is transient, surviving less than one year.

Changes in distribution

As mentioned above, R. lingua has been in decline for perhaps as long as 200 years (Harron 1986; Hackney et al. 1992), a situation demonstrated for the British Isles in the 1962 and 1976 Atlases (Perring & Walters 1962, 1976). This decrease in range is also described for the Nordic countries by Jonsell et al. (2001), where the plant has retreated south of the Arctic Circle (see their map, p. 277). Although changing temperatures may have had some effect on the sexual reproductive capacity of the species further north, it is much more probable that the main factor causing losses in Britain and Ireland was land drainage, since R. lingua is not very sensitive to either water pollution or eutrophication (nutrient enrichment) (Jonsell et al. 2001). However, at least in Britain, if not elsewhere, previous losses have been reversed, as is clearly illustrated by the maps published in the New Atlas (Preston et al. 2002).

Introduction to gardens

During the last 40 years or so, Greater Spearwort has gained appreciation from horticulturalists and is now considered a sufficiently decorative, appropriate and easily enough cultivated subject for planting around the fashionable, indeed almost obligatory garden 'water feature'. Thanks to this trend, there have been so many 'escapes' and deliberate introductions of the plant to the wild in Britain, that Fitzgerald commented, "the distinction between native and alien populations is now hopelessly blurred" (R.A. Fitzgerald, in: Preston et al. 2002).

Irish occurrence

The New Atlas shows that R. lingua is widely scattered and locally frequent in Ireland, but the main areas of concentration are undoubtedly in the C & NE of the island. However, while it may remain scattered in NE Ireland, the area around Upper Lough Erne now appears to constitute the main stronghold of this rather scarce and local emergent aquatic species in the north of Ireland. Harron (1986) described Greater Spearwort as being widespread but very sparingly distributed around Lough Neagh and he considered it was probably decreasing there. Hackney likewise regarded it as rather rare in the three counties in the FNEI 3.

British occurrence

Due to the increased use of the plant in gardens in recent decades, it is almost impossible to distinguish many native populations from introduced populations of R. lingua in S & C England in the New Atlas map (Preston et al. 2002). However, if we mentally subtract the obviously alien concentrations of R. lingua around the major conurbations, the encouraging impression remains discernible, that the species has at least survived in those native areas where it appeared in the earlier BSBI Atlas (Perring & Walters 1976). The better recording coverage in some areas also helps offset some definite losses.

European occurrence

In Europe, the species is widely represented in W & C areas, declining to both N & S, and only occasional and very scattered throughout the Mediterranean region. There have also been significant extinctions in Belgium, N and W France, S Germany and Hungary (Jalas & Suominen 1989, Map 1861).

World occurrence

Beyond Europe, Greater Spearwort ranges from SW Asian Russia (to the Altai), the Caucasus and Kashmir in W Asia. It has been introduced in New Zealand (Hultén & Fries 1986, Map 868). There is very little variation within the species and none of taxonomic importance (Jonsell et al. 2001).

Toxicity

Like other buttercup species R. lingua contains bitter-tasting toxins which undoubtedly help deter cattle and other stock, although it is not specifically reported as being responsible for poisoning any such animals (Cooper & Johnson 1998).

Names

The Latin specific epithet 'lingua' means 'tongue' and refers, quite aptly in this instance, to the shape of the stem-leaves (Gilbert-Carter 1964). The English common names 'Spear-wort' and 'Spear Crowfoot' were applied from the 14th century, again on the basis of the leaf shape, to both the more common R. flammula (Lesser Spearwort) and to R. lingua (Grigson 1974). Thus to distinguish them in modern times, they have been called 'Lesser' for the smaller, narrower-leaved R. flammula and 'Greater' for the larger of the two. The only additional name is 'Sparrow-weed', which Britten & Holland (1886) list only from Co Londonderry (H40).

Threats

Hyper-eutrophication of its habitat, or destruction of the vegetation surrounding the lakes where the plant grows.