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Matricaria discoidea DC., Pineappleweed

Account Summary

Introduction, neophyte, common.

July 1904; Colgan, N.; by railway line at Lisnaskea.

March to January.

Growth form and preferred habitats

An extremely successful, small, erect, branched ruderal weed up to 35 cm tall, M. discoidea is frost hardy and can behave as either a winter- or a summer-annual depending on when it germinates. Once the pineapple odour of the finely divided leaves is smelt, this plant is not easily forgotten. Unfortunately, the strength of the smell is very variable and some plants appear to lack the property altogether.

M. discoidea prefers open habitats offering moist to temporarily dry, weakly acidic to weakly basic, usually fertile, lowland soils. It avoids strongly acidic conditions and, being tolerant of considerable trampling, it frequently occurs in the heavily disturbed, muddy, sometimes compacted soils around field gates, along roadside kerbs, in pavement cracks, urban waste-ground and on the margins of arable fields. While it is mainly lowland, it has been recorded at 845 m on Great Dun Fell in Westmorland (VC 69) (Grime et al. 1988, 2007; Hill et al. 1999; H.J. Killick, in: Stroh et al. 2023).

Flowering reproduction

M. discoidea flowers from May to September; the average plant produces 43 rayless, conical, yellowish-green flowerheads which are little visited by insects and presumably are self-pollinated. In mild weather conditions in N Ireland, the species can flower well into the autumn, although whether or not these later flowerheads produce seed is undetermined. Each inflorescence generates a mean of around 6,500 achenes, although large individuals can produce over ten times this figure (Salisbury 1964; Clapham et al. 1987).

Like its relatives, the Oxeye Daisy (Leucanthemum vulgare) and Corn Marigold (Chrysanthemum segetum), the small achenes lack a pappus. Since the plant occurs mainly in muddy soil by road and trackside gutters, the achenes are most likely spread by rainwash and in mud attached to vehicles and to the feet of animals, including man. Mabey (1996) describes an experimental demonstration of this spread carried out in 1968, but unfortunately he fails to give a correct reference.

A persistent soil seed bank and ready germination during most of the year together allow the species to survive repeated disturbance (Grime et al. 1988, 2007).

History of introduction and spread

First found in Britain between London's Richmond and Kew Gardens in July 1871 (Colgan 1894; Kay & Hutchinson 1993) and probably native somewhere in NE Asia, Pineappleweed is thought to have come to these islands via N America (Ellis 1993). The first three Irish sites were found inland in Co Dublin by N. Colgan in August 1894; ten years later he also found the first Fermanagh plant.

The species did not spread much beyond its original sites until the first quarter of the 20th century when it did so explosively along the verges of the as yet untarred roads and railway tracks throughout B & I. Dispersal was very probably assisted by the development of motorised transport (Salisbury 1964). The amazing speed of the dispersal in C Ireland and the role of rail and road transport are both clearly demonstrated by the records accumulated in Irish Topographical Botany just seven years after Colgan's initial discovery (Praeger 1901).

Fermanagh occurrence

M. discoidea has been recorded in 286 Fermanagh tetrads, 54.2% of those in the VC. It is widespread in a variety of disturbed, artificial, man-made sites, particularly at lower altitudes.

British and Irish occurrence

The dispersal of this neophyte has been so successful it has become the most widespread alien and the 33rd most widespread plant species in these islands (Crawley et al. 1996). The BSBI Atlas 2020 hectad map shows it is near universal across both B & I at this level of discrimination, except on the highest ground in Scotland. The pattern of distribution and coverage is very similar to that of its relatives Leucanthemum vulgare (Oxeye Daisy) and Senecio vulgaris (Groundsel). In the case of M. discoidea, the recording data for Atlas 2020 indicate it is still spreading in both B & I (H.J. Killick, in: Stroh et al. 2023).

European and world occurrence

As suggested above, the centre of origin of M. discoidea is still a little contentious: Hultén & Fries (1986) suggest it should be looked for in the Pacific region of E Asia and north-western N America as the oldest collections of it are derived from there. It spread very rapidly in the 19th and 20th centuries through N America, Europe and parts of Asia. It first arrived in Europe in botanic gardens in Berlin, Breslau and Uppsala (where it arrived in 1840) and it subsequently spread to Kew (Hultén 1971). It also spread more locally to S America and New Zealand, so that the present distribution is almost circumpolar. It is, however, still surprisingly scarce and widely scattered in the Mediterranean region, although it very probably will eventually colonise there too (Hultén & Fries 1986, Map 1808).

In B & I, Pineappleweed spread before roads became metalled and it did the same throughout Europe, N & S America and New Zealand (Clapham et al. 1987; Ellis 1993).

Names

The genus name 'Matricaria' is a medieval name, derived from the Latin 'matrix' meaning 'womb' because at one time it was used in herbal medicine for infections of the uterus (Stearn 1992). The Latin specific epithet 'discoides' translates as 'discoid', meaning 'without rays' and obviously refers to the rayless flowerheads (Stearn 1992). The English common name 'Pineappleweed' is also an obvious reference to the pineapple-like shape and appearance of the rayless flowerhead. The term 'pineapple', the fruit of Ananas comosus, native of tropical America introduced to Europe in the 17th century, refers to a resemblance to an extra large pine cone, such cones having previously been described as 'pine-apples' (Grigson 1974). An alternative English common name is 'Rayless Mayweed' (Clapham et al. 1987).

Threats

None.

References

Salisbury, Sir E. (1964); Kay, Q. and Hutchinson, G. (1993); Mabey, R. (1996); Clapham, A.R., Tutin, T.G. and Warburg, E.F. (1987); Colgan, N. (1894); Praeger, R.L. (1901); Grime, J.P., Hodgson, J.G. and Hunt, R. (1988, 2007); Hill, M.O., Mountfield, J.O., Roy, D.B. and Bunce, R.G.H. (1999); Crawley, M.J. Harvey, P.H. and Purvis, A. (1996); Hultén & Fries 1986; Hultén 1971; Stearn 1992; Grigson 1974; Stroh et al (2023); Ellis (1993).