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Sedum acre L., Biting Stonecrop

Account Summary

Native, scarce or occasional only. European temperate, but widely naturalised including in N America and New Zealand.

1884; Barrington, R.M.; Enniskillen Town.

June to August.

Growth form and preferred habitats

This distinctive, low-growing stonecrop with its perennial fibrous roots, creeping stems and tufts or cushions of annual flowering shoots is the most common and widespread succulent species in B & I, being found in every VC (New Atlas). Nevertheless, it is quite rare and thinly scattered in Fermanagh, where it is found in a range of typical open, dry, shallow and occasionally droughted soils. It grows in sandy and rocky lowland natural or semi-natural habitats of neutral or calcareous reaction. It is also a pioneer colonist of open, man-made habitats, including crevices and the tops of walls or roadside kerbstones in both rural and urban settings. S. acre produces clusters of bright golden yellow, star-like flowers in June and July on often dwarfed branching shoots, and is propagated by its extremely light seeds (each weighing less than 10 millionths of a gram), or by leaves or other fragments of the plant being transported by wind (Salisbury 1964, p. 305; Ridley 1930, p. 29).

Fermanagh occurrence

Altogether S. acre has been recorded in 15 scattered Fermanagh tetrads, ten of them with post-1975 dates. Although it is reputed to be sometimes, or perhaps frequently, deliberately cultivated in gardens (Grime et al. 1988; Grey-Wilson 1989), Robert Northridge and the current author (RSF) have never observed this anywhere in Fermanagh. S. acre is slightly more frequent around the limestone shores of Lower Lough Erne, where it is sometimes found lodged on tops of large boulders.

An ecological study of plants in and around the Sheffield area concluded that Biting Stonecrop, which is slow-growing, is more or less restricted to undisturbed, unproductive, infertile, often rocky situations, which often have little or no soil (ie skeletal soils) (Grimes et al. 1988). In view of this, these workers classified the ecological survival strategy of S. acre as a stress-tolerator, meaning it avoids biological competition by surviving in a far from ideal growing environment. In maritime areas of B & I, S. acre is very commonly met on open, nutrient-depleted, species-rich grasslands, sand-dunes and shingle, sometimes forming quite substantial patches. The survey of soil seed banks in NW Europe listed seed of all species of this genus as transient or indeterminate (Thompson et al. 1997).

British and Irish occurrence

The New Atlas map displays many hectads in Ireland, W Scotland and Cornwall with only pre-1970 records, a fact that suggests this stonecrop species may be in decline.

Uses

The English common name refers to the very acrid, toxic sap obtained from the plant leaves, which strongly deters herbivores. The sap is a notable skin irritant and its pungency gave rise to alternative English names such as Wallpepper and Wall Ginger (Grieve 1931; Cooper & Johnson 1998, p. 69). In herbal medicine, it was an ingredient of a famous worm-expelling treacle or vermifuge. It was also recommended for treating scurvy and useful for intermittent fever and dropsy. Great care is required in terms of dosage, as it can easily cause inflammation and blisters when applied externally (Grieve 1931).

Threats

None.