Anagallis arvensis L., Scarlet Pimpernel

Account Summary

Growth form and preferred habitats

Rather surprisingly, this little sprawling annual is classified as one of the worst weeds in the world, having been accidentally introduced by emigrants almost everywhere around the globe from its native range in S Europe (Holm et al. 1977). Much of the reason for this drastic reputation rests in the fact that this small plant is a very variable and adaptable weed in a wide range of crops, including pulses, cereals, vegetables and oil seed. Despite the small scale of the plant, the species is also dangerously poisonous to a wide range of stock animals (Chrtek & Osbornova-Kosinova 1986). The plant can also cause dermatitis in some individuals if the leaves or stems are handled (Holm et al. 1977).

In our relatively mild, wet climate, A. arvensis is mainly a summer annual. Previously, in B & I, it commonly grew on the field margins of spring-sown crops. It can also behave as a winter annual or even as a facultative perennial, but there is no evidence that it does so in Fermanagh (Grime et al. 1988 & 2007).

Since the 1950s, increasingly effective weed-control measures have made this once familiar agricultural weed and widespread wildflower much scarcer. Nowadays, it is seldom found and then almost always in open, heavily disturbed sites where competition is either absent or slight. Examples include around rural gateways, quarries or near habitation where bird-sown seed (some of which may originate from bird-tables) may establish.

The species can tolerate light shade, but the flower always demands full sun and will close if cloud darkens the sky, a fact that gave rise to the numerous alternative English common names relating to both the clock and the weather, eg 'John-go-to-bed-at-noon', 'Twelve o'clocks' and 'Shepherd's watch', and with regard to weather, 'Poorman's Weatherglass', 'Grandfather's-, Old Man's-, or Shepherd's- Weatherglass', or 'Weather-teller' (Grigson 1987).

Fermanagh occurrence

The Fermanagh Flora Database contains records from a total of 26 tetrads, 4.9% of those in the VC. As the tetrad distribution map indicates, A. arvensis is confined to the lowlands, is very thinly scattered and has declined significantly. Only 15 Fermanagh tetrads contain post-1975 records.

The decline of arable farming together with weed-control has made A. arvensis much more occasional or rare here. Nowadays, it appears in small, ephemeral populations confined to open, heavily disturbed sites, both urban and rural, around gateways, roadsides and quarries or waste ground near habitation.

The only semi-natural situation in which A. arvensis has been recently recorded in Fermanagh is on sandy lakeshores, but even these are grazed and trampled by cattle. The preferred soil is light and sandy, yet neither too dry nor too acidic. The plant can tolerate light shade, but the flower always demands full sun and will close if cloud darkens the sky. 'Scarlet Pimpernel' is something of a misnomer, the normal and virtually constant flower colour in the current author's experience (RSF), being a distinctive orange-red.

Evidence of decline

A pronounced decline in the occurrence of A. arvensis, similar to that in Fermanagh, was found in surveys of Danish arable fields made in 1967-70 and again in 1987-9 (Andreasen et al. 1996). These workers attributed the steep decline of the species to its sensitivity to herbicides, together with low rates of seed production and the plant's lack of competitive ability against modern crop varieties. Rich & Woodruff (1996) analysed changes in the flora of England brought to light by the BSBI Monitoring Scheme, comparing samples from 1930-60 with 1987-8. They found significant reductions in 31 species of arable weeds, but did not include A. arvensis in their list of declining species. The editors of the New Atlas calculated a Change Index, comparing the results of the 1962 and 2002 BSBI Atlas surveys and, for A. arvensis, the negative value is quite large (-0.73). In addition, comment is made that there have been losses in the north of the species range, the timing of which is unknown (A.J. Richards, in: Preston et al. 2002).

Flowering reproduction

Unlike many other ruderal, annual weeds, A. arvensis has quite a short flowering period (June to August) and, although very variable with respect to the environment in terms of the number of capsules produced, overall the species produces a relatively small seed crop, numbering on average just 902 ± 54 seeds per plant (Salisbury 1942, p. 149).

The seed coat of A. arvensis contains a water-soluble germination inhibitor which provides an innate dormant period and the species produces a persistent seed bank. Natural seed dormancy is at least ten years and seed longevity certainly exceeds 16 years, with other estimates ranging up to over 68 years (Thompson et al. 1997).

Flower variation

The English common name 'Scarlet Pimpernel' is something of a misnomer, the normal and virtually constant flower colour in the current author's experience, being a distinctive orange-red. The five (or more) colour variants known are scarlet, pink (or orange-pink or salmon), white, purple (or lilac) and blue, all form a series, in which scarlet is simply dominant to pink, pink to white, and so on across the spectrum. The beautiful blue-flowered variant is recessive to all the other forms, except that when it is crossed with lilac there is segregation in the F₁ generation (Allen 1954). Actually two blue forms of the species exist: A. arvensis subsp. arvensis forma azurea and A. arvensis subsp. foemina, the latter having both narrower upper leaves and petals and with petal margins minus the numerous hairs of subsp. arvensis forma azurea (for full distinction see Stace 1997, p. 301). The forma azurea (Blue Pimpernel) is known to occur in coastal parts of counties Antrim, Dublin and Wicklow (H39, H21 & H21) at least, and the two blue forms are by a long way the most prevalent variants of the species in the Mediterranean region, where they behave as winter annuals. As far as the current author is aware, neither form of the Blue Pimpernel has been recorded in Fermanagh.

Toxicity

The poisonous principles in A. arvensis are not yet properly understood. Aerial parts of the plant are said to contain a glycosidal saponin, while the roots supply another saponin called 'cyclamin'; an acrid volatile oil has also been isolated from the species (Cooper & Johnson 1998). When 31 cattle and buffalo died in India after been fed collected 'greens' with a high proportion of A. arvensis, Sadekar et al. (1995) considered the clinical symptoms, lesions and histopathology pointed to oxalate toxicity. Subsequent analysis showed the plants contained 9-13% oxalic acid on a dry weight basis. In addition to the animals mentioned, in various parts of the world the plant has produced gastro-intestinal, heart, liver and kidney problems (sometimes lethal) in horses, dogs, sheep, rabbits and poultry. The seed has also affected birds (Cooper & Johnson 1998).

Medicinal uses

In the past, the plant was used in herbal medicine as a diuretic and to stimulate bile flow, but fortunately it is now considered completely obsolete in allopathic medicine, although it is still retained in homeopathy for skin complaints such as itching and warts (Launert 1981).

European and world occurrence

Hultén & Fries (1986, Map 1484) regard the Mediterranean basin as the probable point of origin of A. arvensis, from whence it spread as a weed, firstly to C and N Europe and then, more recently, to other parts of the world, carried around by emigrants along with their crop seed. It has now become circumpolar and, indeed, almost cosmopolitan everywhere Europeans became established, although there are wide gaps in the overall world distribution.

Threats

None.

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