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Sagina apetala Ard. s.l., Annual Pearlwort

Account Summary

Native, occasional. European southern-temperate, but widely naturalised.

1900; Praeger, R.Ll.; Co Fermanagh.

May to September.

Growth form and preferred habitats

This small, stress-tolerant winter and summer annual is a pioneer colonist of dry or well-drained, sunny, lowland, open artificial or disturbed habitats where there is a virtual absence of biological competition. It frequently occurs in a wide range of such habitats, including, eg on the tops of walls, in cracks in weathered concrete, between paving stones, on or along forestry tracks and in bare or sparsely vegetated areas of sandy, clayey, and gravelly or otherwise stony soils. The most natural habitats it occupies are gravelly or sandy soils on heaths, sea cliffs and by paths on commons (Sinker et al. 1985; Stace 2010).

Compared with the generally perennial, prostrate, appressed, spreading habit of S. procumbens (Procumbent Pearlwort), the typical S. apetala plant generally has a more diffuse, more upright appearance, growing up to 15 cm tall. Both these species are very tolerant of trampling and they can colonise heavily compacted soil on and near pathways. In such circumstances, they are often extremely dwarfed in height and flattened in appearance.

Flowering reproduction

The erect inflorescence bears 2-7 flowers from June to September. Although the Latin specific epithet 'apetala' translates as 'without petals', S. apetala may sometimes possess minute green petals within the ring of (usually four) sepals. While small crawling insects may visit the flowers, most pollination and fertilisation is probably the result of automatic selfing (Clapham et al. 1962). Seed is produced in considerable numbers, about 50 per capsule. The light and dust-like seed is very readily wind dispersed. Since the plant most frequently occupies disturbed, often trampled ground, seeds may also be carried in mud or hair by animals, or footwear and clothing by man (Salisbury 1964). Estimates of dormant longevity in the soil seed vary from transient up to viable for five years (Thompson et al. 1997).

British and Irish occurrence

S. apetala is common and widespread, especially in urban settings in lowland Britain & Ireland, but it becomes more scattered and scarce or absent in wetter, more acid, peaty conditions, especially on higher ground in the N & W of both islands (New Atlas). There is room for doubt about the accuracy of the distribution of this and related forms, due to confusion regarding taxonomy and identification in recent years, and reassignment and renaming of subspecies (P.S. Lusby, in: Preston et al. 2002). This is especially the case with regard to confusion with S. filicaulis (see Variation below).

Fermanagh occurrence

In Fermanagh, S. apetala in the broad sense has been occasionally recorded in 59 tetrads, 11.2% of those in the VC. In Fermanagh, outside urban and village areas, it is especially associated with ground in and around quarries.

Variation

Previously two subspecies were recognised, S. apetala subsp. apetala and subsp. erecta. However, S. apetala subsp. erecta F. Herm. and var. filicaulis have recently been subsumed into a new species, S. filicaulis Jord. (Slender Pearlwort), which is regarded as containing no less than four named varieties (Sell & Murrell 2018). As is shown below, this new combination has not been recorded in Fermanagh, where identification to subspecific level is only rarely achieved.

European and world occurrence

The total distribution is poorly known due to confusion of S. apetala with S. filicaulis. S. apetala is probably native in the whole of C Europe from Britain and Ireland to Poland and Romania, and southwards to Switzerland and the Pyrenees (Jonsell et al. 2001). Earlier treatment by Hultén & Fries (1986, Map 763) suggests a much wider occurrence in Europe extending east to Greece and south to the Mediterranean islands, and possibly to N Africa. A very similar range is plotted in Jalas & Suominen (1983, Map 919), although they they show it as essentially a W European species, near absent in all of Scandinavia. A. apetala is also widely introduced to remote regions around the world including S Africa, S Australia, Tasmania, New Zealand, E & W coast USA and S America.

Names

The generic name 'Sagina' is Latin, meaning 'food crop' or 'fodder'. Spergula arvensis (Corn Spurrey), which was cultivated and much valued in Flanders as a fodder crop for dairy cows, or as human famine food in the 15th century, was previously called Sagina spergula (Gilbert-Carter 1964; Thirsk 1997, p. 17). The Latin specific epithet 'apetala' refers to the petals being absent (or almost so – see Flowering reproduction above). The English common name is a typical book name of no folklore significance.

Threats

None.