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Anthemis cotula L., Stinking Chamomile

Account Summary

Introduction, archaeophyte, a very rare casual and locally extinct. European southern-temperate, but widely naturalised in both hemispheres.

1900; West, W.; cultivated ground in Enniskillen Town.

Growth form and preferred habitats

An annual weed of arable crops and farmyards, like other Chamomile and Mayweed species, A. cotula has daisy-like flowerheads and very finely dissected foliage, but it can be distinguished by its lack of hairs (glabrous) or almost so, ie sparsely hairy, or subglabrous as Salisbury (1964) puts it. In common with most other 'Mayweeds', A. cotula possesses a strong, aromatic scent but, in this instance, the odour given off by glands on the leaves when they are rubbed is very definitely malodorous, unpleasant, or even foetid and stinking, depending on the sense of smell of the individual smelling it! Gerard (1597, 1633) said it had, "a naughty smell". The fluid secreted by the foetid glands is also so acrid it can burn skin, a fact that made it a hated weed in the days of hand harvesting of crops and hay (Grigson 1955, 1987; Salisbury 1964; Kay 1971).

A. cotula can germinate in both the autumn and in spring so can behave either as a winter or a summer annual. The plant is phenotypically very variable and plastic with response to minor changes in environment, plants displaying a wide range of size and habit (appearance, degree of branching, etc) when growing in a varied environment, such as what we might characterise "normal farmland" (Kay 1971). However, the species typically grows erect, 20-50 cm tall, branching above to produce a corymb of terminal, daisy-like, white-rayed flowerheads.

A. cotula typically behaves as a pioneer colonist of lowland, open weed communities in cereal fields and other arable crops, and it appears very much more rarely in disturbed, semi-ruderal waste ground and, then, usually near farm buildings (Kay 1971; Sinker et al. 1985). The established strategy of A. cotula is characterised as 'R', meaning a straightforward Ruderal (Grime et al. 1988, 2007). It favours heavy, damp, sometimes winter-wet clay, clay-loam or marl soils, especially if they are base-rich, but can grow less commonly on soils of medium texture and also rarely on lighter, somewhat drier ones, including those over chalk. The association of A. cotula with heavy soils is very strongly marked (Kay 1971; Sinker et al. 1985). It can persist as a weed of under-sown ley grass, overwintering in stubble, reappearing and flowering in the spring (Kay 1971).

On account of its acrid, odorous leaf glands, the plant is unpalatable to grazing animals, which avoid it unless they are near-starving (Salisbury 1964). The species is able to withstand moderate levels of trampling and frosts do not harm its overwintering leaf rosettes. It is, however, susceptible to drought, plants becoming extremely dwarfed under such growing conditions (Kay 1971).

Roadside populations have typically always consisted of just a few plants and as the species has declined over several decades, this is now true in the majority of sites in B & I where it manages to survive. Isolated, solitary plants are also more frequent than was observed in the past and they usually set few, if any, seeds, since they are unlikely to be cross-pollinated (Kay 1971). Like most annuals, the size of the plant is very plastic and variable with respect to immediate environmental conditions, ranging from miniscule 5-10 cm tall specimens, to large, well branched, tall, spreading individuals that can produce several hundred flowerheads. The species is susceptible to modern herbicides, which offer farmers a high level of weed control (Kay 1971).

Flowering reproduction

Effective reproduction is entirely by seed. A. cotula flowers from May to July, and if growing in an arable crop, after the crop has been harvested, it flowers again in the stubble in September and October (Garrard & Streeter 1983). The daisy-like flowerheads are usually less than 2.5 cm in diameter, slightly smaller than those of the closely related A. arvensis (Corn Chamomile) and, as they age, the disk of yellow, tubular, bisexual flowers becomes conical and the sterile white ray-florets that surround them bend downwards, a distinguishing feature that is in marked contrast to the almost flat flowerheads characteristic of A. arvensis (Salisbury 1964).

Average sized plants (25-30 cm tall) usually produce somewhere between ten and 25 flowerheads and the flowers are almost entirely self-incompatible. It is worth remembering that nothing is absolute in biology, but A. cotula is normally over 90% self-incompatible (Q.O.N. Kay: in Stace 1975). The flowers are cross-pollinated mainly by hoverflies and other flies (Kay 1971; Garrard & Streeter 1983). The average-sized flowerhead produces 50-75 achenes. Seed set is very dependent on insect activity and prolonged periods of poor flying weather, cold autumns, or insect population depletion by insecticide spraying, all seriously affect seed production (Kay 1971).

The fruit and its dispersal

The achene fruits are yellow-brown, 2 mm long, "with 10 ribs bearing pimply bosses" according to Salisbury (1964) or small tubercles (Perring & Walters 1989). There is no pappus, the achene being topped by an inconspicuous rim. There clearly are no structural adaptations to enable seed dispersal, but the mature achenes are less densely packed together than those of A. arvensis (Corn Chamomile). The central achenes drop off the ripe flowerhead quite readily, while those on the lower margin of the domed receptacle can become cupped by the involucral bracts and retained on the plant being transported in hay contaminated by the species. The achenes may also be transported on clothes and in mud adhering to machinery and the feet of animals, including human footwear (Kay 1971).

Seed germination and longevity

Being an annual, seed germination principally takes place in both autumn and spring, but it can occur at any time of year (Kay 1971).

There are ten estimates of seed longevity listed in the survey of seed banks in NW Europe, which reflect all four seed bank types recognised: three suggest seed survival is transient (less than one year), two that it is short-term persistent (one to five years), four that it is long-term persistent (at least five years) and one that is unable to decide which category to place it in (Thompson et al. 1997).

Hybrids

A. cotula is reported to be able to hybridise in C Europe with four closely related Chamomile and Mayweed species, A. tinctoria (Yellow Chamomile), A. arvensis, Tripleurospermum inodorum (Scentless Mayweed) and Matricaria recutita (Scented Mayweed) (Kay 1971). Only the intermediate intergeneric hybrid with T. inodorum has ever been recorded in Britain and that extremely rarely (Kay 1971; Stace et al. 2015).

Fermanagh occurrence

There has only ever been a single record of A. cotula in Fermanagh as listed above. For comparison, in immediately adjacent Co Tyrone (H36), there are just two records for A. cotula, both very old: Doon Point, Belfast Naturalists' Field Club, 1914; and Killycolpy, Greer, 1934, both reported in McNeill (2010).

British and Irish occurrence and status

In both the distant past and the early 20th century, A. cotula was formerly a widespread, but casual and non-persistent ruderal weed of arable agriculture and waste ground throughout almost all of Ireland, with records from 37 of the 40 Irish VCs (Cen Cat Fl Ir 2). It was often recognised in Ireland as having been introduced as an impurity with agricultural seed (Stewart & Corry 1888), or with grain or animal fodder (eg Brunker 1940). Stinking Chamomile had therefore generally been considered as 'probably introduced' in Ireland (Cen Cat Flora Ir 2). The current author (RSF) finds it puzzling that it needed someone of the authority of Prof D.A. Webb (1985) to eventually state that he was absolutely convinced A. cotula was accidentally introduced along with grain crop seed. Webb (1985) then suggested the same situation and status might well be true in Britain. The editors of the New Atlas followed Prof Webb's lead and declared A. cotula an ancient introduction, an archaeophyte, a weed of arable farming, probably present in B & I since the Iron Age (H.J. Killick, in: Preston et al. 2002). This view was further confirmed by research on the topic of status carried out and presented by Preston et al. (2004).

Species decline

A. cotula began to decline in B & I at the end of the 19th century, its demise attributed to a combination of the increased efficiency of seed cleaning, weed control methods and changes in agricultural practice (FNEI 3). The marked decrease of the area under tillage in B & I as a whole since the 1950s, a feature that is particularly noticeable in Fermanagh, has hastened the decline of this annual and it is now considered locally extinct in the county, having not been seen since West's solitary record of 1900. The Change in the British flora survey of 1987-2004 (Braithwaite et al. 2006) and the Atlas 2020 hectad map both indicate that A. cotula has experienced a spectacular decline across lowland B & I, especially in Ireland, Scotland and N England. It has, however, managed to hang on to a limited extent as an increasingly uncommon species in C & S England, especially south of a line between Bristol and Hull (Stroh et al. 2023). Populations are often very small and local, however, as recent county Floras indicate (in England and Wales: Brewis et al. 1996; Beckett & Bull 1999; Crawley 2005; and Chater 2010; in Ireland: Reynolds 2013; Green 2022).

European and world occurrence

A. cotula belongs to the European southern-temperate phytogeographical element and is believed to be probably indigenous in the Mediterranean region. It is very widely introduced with agricultural seed extending north into Scandinavia including C Sweden, S Norway and S Finland. The distribution includes N Africa, the Canary Isles and W Asia and it has been accidently introduced with grain to N America, Argentina, Australia and New Zealand (Hultén & Fries 1986, Map 1803; Sell & Murrell 2006).

Uses

Although A. cotula is regarded as a toxic weed on account of its ability to blister bare skin, it still has been used as a medicinal herb in the past. It was considered to have tonic, antispasmodic, emmenagogue (ie it stimulated or increased menstrual flow) and emetic (ie caused vomiting) properties. It was also used as a sudorific in treating colds and chronic rheumatism, for headaches, in convalescence from fevers, for treating scrofula and hysteria (Grieve 1931). An unguent made from it was also used to treat old sores that would not heal. Stinking Chamomile was also claimed to have been used as a powerful insect repellent, although Allen & Hatfield (2004) cast doubt on some of the properties claimed, saying they were, "too unspecific to be accepted without fuller evidence".

Names

The genus name 'Anthemis' is probably derived from the Greek 'anthemon' meaning 'a flower', and could, therefore, be said to mean 'flowery'. The name was applied to a plant by the ancient healer Dioscorides (Gilbert-Carter 1964; Gledhill 1985). The Latin specific epithet 'cotula' means 'small cup' or 'cup-like', probably referring to the flowerhead (Johnson & Smith 1946).

No less than 25 local English common names are listed by Grigson (1955, 1987), six of which have the word element 'dog', (eg 'Dog's Fennel'), which always indicates a negative, unfavourable complexion regarding some feature(s) of the plant. In addition to 'Stinking Chamomile' (see the current author's Matricaria recutita (Scented Mayweed) account), this species is regularly referred to as 'Stinking Mayweed'. The familiar name 'Mayweed' dates to the 15th century when it appeared as 'Maydewede', from the Anglo-Saxon 'Maegthe' and the Old English 'mægthe', of which 'Maythe', 'Maythen' 'Maithen', 'Maitheweed' and 'Maise' survive in some areas, and which may be akin to 'Mægth', meaning 'a maid', perhaps a reference to the rather pretty-looking white flowers (Grigson 1955, 1987 and Grigson 1974).

Threats

None any longer, since it is locally extinct in Fermanagh and elsewhere in B & I it is in rather steep decline.

References

Webb, D.A. (1985); Scannell, M.J.P. and Synnott,D.M. (1987); Hackney, P.( Ed.) and Beesley, S., Harron, J. and Lambert, D. (1992); Preston et al. (2002); Preston et al. (2004); Brunker 1940; Salisbury (1964); Kay 1971; Garrard & Streeter 1983; McNeill (2010); Thompson et al. (1997); Stroh et al. 2023; Perring & Walters 1989; Grigson 1955, 1987; Grigson 1974; Gerard (1597 & 1633); Grieve 1931; Allen & Hatfield (2004); Brewis et al. 1996; Beckett & Bull 1999; Crawley 2005; Chater 2010; Reynolds 2013; Green 2022; Gilbert-Carter 1964; Gledhill 1985; Johnson & Smith 1946; Braithwaite et al. 2006; Hultén & Fries 1986, Map 1803; Sell & Murrell 2006; Grime et al. 1988, 2007. Sinker et al (1985); Stace (1975); Stace et al (2015); Stewart & Corry (1888)