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Euphorbia exigua L., Dwarf Spurge

Account Summary

Introduction, archaeophyte, a very rare casual, now locally extinct. European southern-temperate.

1952; MCM & D; waste ground by railway at Belcoo.

Fermanagh and Irish occurrence and decline

There is just one 1952 record for this small, 5-20(-30) cm, erect, ± glaucous, ruderal annual spurge in Fermanagh. Meikle and co-workers in their 1975 Revised Typescript Flora commented that it is hardly more than a casual in the VC. Principally a weed of lowland arable farming with fibrous roots and a slender taproot and flowering nearly all year round, it prefers light, dry, base-rich soils and open sunny situations; E. exigua was always quite a rare plant in NI where such specific growing conditions were fairly uncommon (Hutchinson 1972). Dwarf Spurge does not stray far from arable fields and only rarely features on other forms of disturbed ground including gardens and bare patches in waste ground. Nowadays, it is all but extinct in NI. The New Atlas map plots a solitary hectad with a post-1987 record in Co Armagh (H37).

Elsewhere in Ireland, according to the 1987 Cen Cat Fl Ir 2, Dwarf Spurge was previously recorded in all but four of the 40 VCs (S Kerry (H1), W Mayo (H27), Sligo (H28) and Fermanagh (H33) and was chiefly found in the east and centre of the island, but with the major decline in arable tillage and the expansion of intensive farming practices involving changes in crop management, increasing pasturage, reseeding, the use of broad-spectrum herbicides, increased fertilizer application and the development of competitive crop varieties, this weedy little spurge naturally and unnaturally declined everywhere. In most of Ireland, the major decline of E. exigua took place around the 1930s and 1940s, thus preceding this major agricultural shift and intensification, but it is now a rare and definitely dwindling species presence that is categorised as 'Near threatened' in the Ireland Red List No. 10 Vascular Plants (Parnell & Curtis 2012; Wyse Jackson et al. 2016).

Good examples of the historic contraction of E. exigua are found in Cos Wicklow (H20) and Dublin (H21): in his Flora of the County Wicklow, Brunker (1950) regarded the species as rare and he listed all known VC records from 1866 to 1932, a total of just eight localities. In adjacent Co Dublin, immediately to the north, Colgan (1904) regarded E. exigua too common a cornfield weed to list localities. By 1961, when a Supplement to Colgan's Flora was published (infuriatingly without an index to either genera or species – but on p. 60), Dwarf or Cornfield Spurge is listed as 'occasional', although only one 1947 station, on the banks of the River Dodder, is actually listed. The understated accompanying comment was, "Apparently not so common as in Colgan's time." (Brunker et al. 1961). In comparison, the most recent (1998) Flora of Co Dublin listed a total of six stations for E. exigua located during the 1984-93 recording period (Doogue et al. 1998).

While the peak level of this casual weed species presence and the timing and rate of decline must have varied locally to a considerable but now unknown extent, this did not stop Praeger & Megaw (1938) from claiming in the 2nd edition of the Flora of the NE of Ireland that Dwarf Spurge was a, "frequent and locally abundant colonist" among crops on light soils in all three VCs covered (Down (H38), Antrim (H39) and Londonderry (H40)). Fifty years earlier, the first edition of this local Flora by Stewart & Corry (1888) was more circumspect in its appraisal, describing E. exigua as, "rare but locally abundant", and in Co Londonderry (H40) as, "common in cornfields, and in sandy or gravelly land".

Status in Britain and Ireland

While always regarded as introduced or probably introduced in Ireland, E. exigua has previously and traditionally been assumed native in most Flora accounts in Britain prior to 2012. Stace (1997), for instance, was unusual in considering it, "probably native". However, Webb (1985) listed it among 41 species he believed were probably introduced to Britain by man. Subsequently, Preston et al. (2002 & 2004) carried out the necessary analysis of the available circumstantial evidence and they have declared it an archaeophyte, vindicating Webb's opinion.

British occurrence

E. exigua remains fairly common and widespread in SE & C England, but is much less common in the N & W of Britain and in Wales where it has always been more or less coastal. Losses in the N & W of Britain were occurring before 1930 and, elsewhere, continue into the present day due to intensification of farming (J.H.S. Cox, in: Preston et al. 2002).

European and world occurrence

The species belongs to the European Southern-temperate element and probably originated in the Mediterranean region. It remains widespread in W Europe stretching north into mid-Norway (around 65oN), N Sweden and S Finland, Atlantic Isles (Azores), N Africa, eastwards to Palestine and N Iran. It was introduced and naturalised in some of these northern areas, probably as an agricultural seed contaminant and was also introduced into N America, SE Australia and New Zealand (Clapham et al. 1987; Hultén & Fries 1986, Map 1283).

Threats

None.