Caltha palustris L., Marsh-marigold

Account Summary

Growth form and preferred habitats

A perennial with a short, thick, rather tuber-like horizontal rhizome, C. palustris occurs in a very wide variety of wet habitats, including the margins of rivers, streams and ditches, in wet woods and fen carr around lakes and ponds where it grows well in partial shade in low-lying ground. Vegetative growth begins early in the year and, like Ranunculus ficaria (Lesser Celandine) and Anemone nemorosa (Wood Anemone), it is pre-vernal in its flowering when growing in deciduous woodland. It also occurs more locally in seasonally flooded meadows and pastures where it can sometimes form large dominant patches, but it does not tolerate permanently flooded ground (Grime et al. 1988).

Typically C. palustris prefers neutral to base-rich mineral or fen-peat soils, rather than very acidic ones and it is, therefore, rare or absent on boglands and on soils with a pH below about 4.5 (Grime et al. 1988). Like several other members of the Ranunculaceae, it tends to frequent areas of disturbed ground with relatively high exposures of bare earth and it often grows on banks of streams and lakes close to the water's edge where fluctuating water levels help minimise competition from taller, tufted, potentially dominant emergent species (Grime et al. 1988). As with most wetland species, it is chiefly found in lowland situations, but it is known to ascend to 1,100 m in Scotland (Wilson 1949). With increasing altitude the species occurs more frequently in open, completely unshaded situations.

Reproduction

In the normal upright growth form of the plant there does not appear to be any form of vegetative propagation, rather reproduction and dispersal relies entirely on seed. However, Grime et al. (1988) reported that shoots detached during disturbance are capable of regeneration, a feature which deserves to be further investigated, since, for example, trampling by grazing livestock and drain cleaning operations must often result in plant fragmentation.

The showy and very familiar flowers of Marsh-marigold are produced early in the year from March onwards and, depending on the season, they continue flowering through to July or even August. The flowers are petal-less but have five to eight sepals, glossy yellow above, often greenish beneath, which take on the protective and insect-attracting, advertising roles of petals. Flowers of C. palustris are self-incompatible and are visited and pollinated by a variety of insects, including flies, bees and beetles, which collect both nectar (secreted by the several carpels at their base and, therefore, partly concealed, though generally copiously produced) and plentifully produced pollen as food sources (Hutchinson 1948, p. 139; Proctor & Yeo 1973; Fitter 1987; Jonsell et al. 2001).

Fruit and seed production

The distinctive star- or crown-like fruit (hence the English common name 'Kingcup'), usually contains five or six compartments (ie follicles), which split open along their upper sides to reveal a double row of seeds (Melderis & Bangerter 1955). Salisbury (1942) found that a considerable proportion of the ovules formed normally abort, so that while the usual number of ovules per follicle is 17 or 18, the number of seeds is generally much fewer, the calculated mean being nine per follicle. The average plant examined by Salisbury (1964) produced 2,700 seeds, though as Butcher (1961) earlier pointed out, the species is very variable in both reproductive and vegetative respects, and therefore such estimates should be regarded as merely a guide.

Seed dispersal

There is no specialised seed dispersal mechanism: seeds simply drop out of the boat-shaped open follicle and since they possess a corky swollen attachment, they may float for between one and four weeks (Ridley 1930, p. 198; Jonsell et al. 2001). After flowering the leaves of the plant have been observed to increase very considerably in size (Step & Blakelock 1963).

Seed germination and longevity

Caltha seeds have a well-defined chilling requirement which ensures that they remain dormant during winter and germinate in the spring (Grime et al. 1988). A survey of soil seed bank data in NW Europe has provided information from 18 sources, 12 of which regarded the seed as transient, two as short-term persistent (ie surviving for 1-5 years), and two as long-term persistent (ie surviving for at least five years). The two remaining studies were undecided as to which category the species fitted (Thompson et al. 1997). Clearly there is no consensus on this important matter and further study is required.

Genetic variation and the 'creeping' form: In the Typescript Flora of Fermanagh, which details finds up until the early 1950s, Meikle remarked on variants of C. palustris with slender, hairless, creeping stems rooting at the nodes and bearing sparse inflorescences of small flowers that are frequent on lake shores and in wet woods in Castlecoole and elsewhere in Co Fermanagh. The extremes of variation in C. palustris are very distinct and the different forms are said to remain distinct (though rather less so) in cultivation. However, it is not easy to distinguish them satisfactorily from typical C. palustris at a taxonomic level, because numerous intermediate forms exist. Stace (1991, 1997) believes that these few-flowered, procumbent plants are best recognised as var. radicans. In the critical Flora Nordica volume 2 (Jonsell et al. 2001), Piirainen elevates this variety to subspecific level as subsp. radicans (T.F. Forst.) Syme. Whatever we decide to name it, this creeping form was first recorded in Fermanagh by Barrington (1884) as C. radicans (Forst.), and although Meikle states that the variant has been recorded by him and his co-workers in all four of their district subdivisions of the county (Meikle et al. 1975), subsequent local recorders have tended to ignore the form, and in fact there are just three records of this form of the plant in the Fermanagh Flora database. The prostrate creeping form of the plant spreads both by seed and by rooting shoots, so it definitely demonstrates vegetative reproduction. The seeds of this form of the plant lack the corky appendage and do not float, which must restrict its dispersal considerably (Jonsell et al. 2001, p. 331).

Genetically, in terms of chromosome numbers, C. palustris contains a polyploid series ranging from diploids to octoploids, plus a number of aneuploid

forms. However, the chromosome variation is not correlated with variation in form, nor with geography (for details see Jonsell et al. 2001, p. 329).

It is interesting to note that argument regarding the taxonomy of C. palustris and the status of its varieties has rumbled on since 1768, when Philip Miller produced the 8th edition of his Gardeners Dictionary. [NB There is no apostrophe in Gardeners in the original work]. In this work he proposed distinguishing Caltha minor for montane (ie upland) plants having round, crenate, heart-shaped leaves and smaller flowers than normal C. palustris. This suggestion was made only 15 years after the Swedish taxonomist, Carl Linnaeus, described and named C. palustris (Panigrahi 1955). Despite its age, the author of this latter paper has conveniently summarised the history of the debate on the several forms of C. palustris, their morphology, cytology and geography. Panigrahi gives full weight to several significant contributions based on Irish material by Robert Lloyd Praeger. Anyone requiring a more modern treatment of the subject should consult Woodell & Kootin-Sanwu (1971) or Jonsell et al. (2001).

Grazing and toxins

The fact that it can become so prevalent in wet grassland is unfortunate for the farmer and his animals, since like other members of the Ranunculaceae, Caltha contains a significant quantity of the dangerous toxin protoanemonin (for details of this poison see the Ranunculus acris synopsis). This makes plants acrid tasting and they are avoided by stock animals to such an extent that Cooper & Johnson (1998) have not reported any recent cases of poisoning in the British Isles. Salisbury (1964) comments that C. palustris acts as a purgative and that it leads to diminished milk production in cattle which graze it. He also reports it being known to cause death in both cattle and horses.

Fermanagh occurrence

Marsh-marigold is the tenth most frequently recorded vascular plant in Fermanagh in terms of records and it is the ninth most widespread species in the VC, being found in 376 tetrads, 71.2% of our total tetrads. It is absent only from the highest altitudes, permanently flooded, or excessively acidic soils below pH 4.5.

British and Irish occurrence

C. palustris is common and very widespread throughout Great Britain, but is absent from areas of intensive farming such as Cambridge. It is also common and widespread in Ireland, but more or less absent from the more acid boglands of the S & W. Rather remarkably, it is a rare and introduced species in the Channel Isles (Garrard & Streeter 1983; Preston et al. 2002). Despite the destruction of many wetland areas in Britain and Ireland during the past 40 years, the index of change calculated and provided in the New Atlas is -0.26. At least at the hectad scale, this suggests there is little evidence of any change in the species distribution in these islands (R.A. Fitzgerald, in: Preston et al. 2002).

Fossil record

Seed and pollen of C. palustris are well represented in the fossil record although Caltha type pollen also includes Aquilegia vulgaris (Columbine). Godwin (1975, p. 119) suggests that the abundance of site records in the Late Weichselian ice age, strengthens the possibility that the species, "survived the glaciations in this country". One has to presume that as an English writer Godwin was referring to his native island (Great Britain) alone, but perhaps he did not mean to be so insular, and really meant to specify periglacial survival of C. palustris in all unglaciated areas within Britain and Ireland. An opinion on this matter from a suitably qualified authority would be appreciated.

World distribution

In Europe, C. palustris is widespread in both temperate and Arctic areas, but in Europe it becomes scarcer towards the south and around the Mediterranean, reaching only N Portugal. It is absent from the Greek Peloponnese and from all the Mediterranean islands (Jalas & Suominen 1989). Due to differing views of the taxonomy of Caltha palustris, the species has been mapped in different ways; for example, Hultén recognises and maps several different subspecies so that it becomes necessary to mentally combine these variants to achieve an overall picture (Hultén 1971, Maps 75 & 76). Once this is done, C. palustris in this broad sense is shown to be circumpolar in Arctic and boreal, northern temperate regions.

Uses

Considering the fact that the plant is not a Near Eastern nor a southern species, and thus it never attracted the attention of the older Classical civilisations who handed on a knowledge of plants and their uses to Mediaeval and Renaissance Europe, the long list of English common names that Grigson provides must derive almost entirely from the colourful show the plant makes in the countryside and in the water garden. Its prominence, even in habitats disturbed by man and his animals, and the religious and folk beliefs associated with it, rather than any widespread use in folk or herbal medicine, must have made Caltha palustris very much a favourite plant (Grigson 1987).

Being a severe irritant and causing blisters, it was widely known to have caused serious effects when attempts were made to use it in herbal medicine. Nevertheless, it did have some medicinal use associated with mythical beliefs on the treatment of fits (Grieve 1931, p. 519). The leaves were also boiled and eaten like spinach and flower buds were occasionally used like capers − although even Grieve regarding this type of usage as "rather inadvised" [my italics].

Names

The genus name 'Caltha' is derived from the Greek 'kalathos' meaning 'a cup', a reference to the bowl-like shape of the flowers. The Latin specific epithet 'palustris' means 'of marshes' (Melderis & Bangerter 1955). C. palustris has a huge number of English common names. Grigson (1987) lists no fewer than 93. The most widespread English name, 'Marsh-marigold', refers to its use in church festivals in the Middle Ages, as a flower devoted to the Virgin Mary. Several other names also refer to Mary and to May-Day festivals (Grieve 1931; Grigson 1987).

Threats

Many of the plant's meadow sites are vulnerable to drainage operations and could easily be destroyed. However the plant is so widespread and abundant in Co Fermanagh that the threat level to the species is nil.

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