Euphorbia helioscopia L., Sun Spurge
Account Summary
Introduced, archaeophyte, occasional. Eurasian southern-temperate, but naturalised in N America and now circumpolar.
1882; Stewart, S.A.; Co Fermanagh.
April to November.
Growth form and preferred habitats
A taller (20-45 cm), hairless and somewhat more robust, weedy spurge than either E. peplus (Petty Spurge) or the locally extinct E. exigua (Dwarf Spurge), the oval, yellow-green leaves, that are finely toothed in their upper part, make Sun Spurge an easy species to identify. Plants on poor dry soils may be very dwarf, but still manage to flower. E. helioscopia frequently has an erect, unbranched stem below, but above it terminates in regular side branches that give the entire plant a candelabra-like appearance (Salisbury 1964).
Like the other two spurges mentioned, Sun Spurge is a quick growing summer-annual, ruderal of open habitats and appears in and on the margins of cultivated and disturbed ground in gardens and near habitation, plus in arable root and leaf crops, waste ground, soil heaps, roadsides, or in gravel or pavement cracks (Grime et al. 1988, 2007). E. helioscopia is also similar to its two relatives in terms of its preferred ecology, being essentially a plant of dry or well-drained, near-neutral, calcareous or base-rich soils. As its current English common name 'Sun Spurge' suggests, it grows best in sheltered, lowland, sun-warmed sites. The Latin specific epithet 'helioscopia' means 'turning towards (or following) the sun'.
Fermanagh occurrence
In Fermanagh, E. helioscopia usually occurs as isolated individuals or in rather small populations, never appearing in any great quantity. It is thinly but widely scattered throughout the lowlands, particularly in the SE of the county where the better agricultural land lies. In terms of frequency, E. helioscopia is very similar to E. peplus, being found in 29 Fermanagh tetrads, 5.5% of those in the VC. Ten tetrads have pre-1975 records only, a fact which RHN and the current author (RSF) believe reflects the casual nature of the occurrences of this weedy species.
Flowering reproduction
Both E. helioscopia and E. peplus flower from May to October or November. The inflorescence is an umbel, usually with five main rays and yellowish-green bracts similar in shape to the leaves. The small groups of flowers that make up each inflorescence consist of a single female and a few male flowers, all without perianth parts, held in a cup-like axillary structure called a cyanthium. This has 4-5 small teeth alternating with conspicuous green glands at the top. The female flowers have three styles, each with bifid stigmas. The ovary is 3-celled, with a single ovule in each cell, and it is carried on a pedicel (stalk) that elongates in fruit. The flowers are pollinated by small flies and the resultant fruit is a 3-valved, globose, smooth capsule, c 2.5 cm in diameter (Sell & Murrell 2009).
The seed number per plant varies from 600-700 (Guyot et al. 1962) and the mean seed number is 257 per plant (Pawlowski et al. 1970). The seeds of Sun Spurge are very much larger than those of E. peplus, weighing on average 0.00248 g, five times the mean weight of the latter, and they are of the order of size approaching that of typical woodland perennials, ie plants of closed, shaded vegetation (Salisbury 1942, pp. 23-4). Compared with smaller, lighter propagules, the large seed of E. helioscopia may create dispersal difficulties associated with fewer numbers and less ready transport. However, this could be more than offset by greater competitive ability at the extremely critical stage of seedling establishment.
In common with other spurges, E. helioscopia seeds are released by the sudden splitting of the 3-lobed fruit capsule which throws the three contained seeds a short distance from the parent plant. The seed possesses an elaiosome nutritive oil body (sometimes called a caruncle), that attracts ants, and it helps scatter the seed, minimising possible seed predation (Salisbury 1964). Again, as with other ruderal spurges, a small proportion of E. helioscopa seed can survive dormant in the soil for many years (more than five) and some estimates reckon this could be for over 20 years (Thompson et al. 1997).
British and Irish status and occurrence
Although Stace in the New Flora of the BI (1997) still regarded E. helioscopia as native in B & I, it is now considered an archaeophyte. Its date of introduction is unknown, but believed to be prior to 1500 AD (Preston et al. 2004). Sun Spurge is widespread and common throughout most of lowland B & I, becoming less frequent and more coastal northwards in Scotland and westwards in Ireland. There has been no change in the overall distribution of E. helioscopia during the last 60 years, except for a slight decline at the margins of its range (J.H.S. Cox, in: Preston et al. 2002).
European and world occurrence
E. helioscopia probably originated in the Mediterranean area and in W and possibly E Asia. It has spread as a common agricultural weed of root and leaf crops across most parts of the world, including B & I, N Europe, S Africa, N & S America, Hong Kong, Australia and New Zealand (Hultén & Fries 1986, Map 1282). It is a more casual weed in the extreme north of Europe and has become circumpolar (Clapham et al. 1987).
Toxicity
All spurge tissues contain a poisonous milky white latex sap that exudes when the plant is cut or crushed. The toxic principles still require further elucidation, but a resin, an alkaloid (euphorbin, euphorbine or euphorbane), a glycoside, dihydroxycoumarin and other complex compounds such as a diterpene ester called ingenol mebutate have been reported in various Euphorbia species. The poisonous action of the toxins is not affected by drying and storage, so that feeding dried fodder crops containing spurges could still poison animals. Having said this, very few cases have been reported in Britain (Cooper & Johnson 1998).
E. helioscopia caused severe swelling and inflammation of the mouth, salivation and some diarrhoea in sheep allowed to graze a field of poorly grown kale that was infested with Sun Spurge. The animals recovered fully when transferred to good pasture (Cooper & Johnson 1998).
The milky latex is very caustic and quickly burns and irritates skin with which it comes in contact. Even handling broken stems (eg after weeding) and then touching the face, especially around the eyes, is a very bad idea, resulting in painful regret.
Uses
The corrosive latex has a universal reputation for removing warts, as has that of the even more common garden weed, E. peplus, and the much rarer E. hyberna (Irish Spurge) endemic to S & W Ireland. In NE Scotland, E. helioscopia was used against ringworm, while in SE England it was recommended as a poultice for adder bites and other venomous wounds. An unusual and rather dangerous use in Northumberland was as an infusion of the plant, drunk twice daily, to relieve the pain of chronic rheumatism (Allen & Hatfield 2004), perhaps by fatally poisoning the patient! The internal use of the latex has been abandoned by herbalists owing to the severity of its action (Grieve 1931, p. 764).
Names and folklore
Grigson (1987) lists a total of 25 English common names from around B & I for E. helioscopia and Vickery (2019) tops this with 29 names, five of which refer to the famous wart cure, 'Wart-grass', 'Wart-gerse', 'Wart-weed', 'Wartwort' and 'Wret-weed' (another form of 'Wart-weed'). Gerard (1597, 1633) is quoted as saying that the juice or milk, "cureth all roughness of the skinne, mangines, leprie, scurffe, and running scabs, and the white scruf of the head. It taketh awaie all maner of wartes, knobs, and the hard callouses of Fistulaes, hot swellings and Carbuncles". An excellent name (highly appropriate) listed by Vickery (2019) is 'Little good', or variants such as 'Little giddie', 'Little gweedie', 'Little guid' and 'Littlegude, the Devil'.
Threats
None.