Linum catharticum L., Fairy Flax, or Purging Flax
Account Summary
Native, common and widespread. European temperate, but also in N America.
1881; Stewart, S.A.; Co Fermanagh.
Throughout the year.
Growth form and preferred habitats
The unbranched, slender, wiry stems, 5-30 cm tall, of this little biennial (or rarely annual) ruderal herb, with its small opposite, sessile, well-spaced, wintergreen leaves (5-12 mm long), remain attached to its tap-root and shallow fibrous roots all winter, so that the species is identifiable throughout the year. Although individuals are short-lived, the species is a constant and sometimes abundant plant of species-rich, short turf in unimproved, infertile, limestone grassland growing on sunny, dry or winter-wet, rocky or stony, calcareous or base-rich soils.
As the words 'purging' and 'catharsis' associated with its English and botanical names suggest, and despite its small size, L. catharticum contains significant toxins (eg linamarin, a cyanogenic glycoside), so that stock animals know to avoid it (Cooper & Johnson 1998). It therefore tolerates grazing very well and is prevalent on upland rocky pastures.
Fairy Flax is also found in a range of other habitats including short-sedge dominated flushed ground on moderately acidic heaths, in winter-wet marshy grasslands and in the drier parts of lime-rich fens, common enough around Upper Lough Erne. Both in the uplands and in the wetter ground, L. catharticum is particularly associated with sites that are either steep, rocky, swampy or otherwise inaccessible to farm machinery. This type of ground means the vegetation cannot be sprayed with agrochemicals, and where the ground is too rocky, or the soil too shallow, it is also impossible to plough and reseed, so the species manages to avoid major agricultural disruption and can persist.
Variation
Two varieties have been named: the standard form, var. catharticum has solitary stems 5-30 cm, usually branched only in the inflorescence and leaves, oblong, 5-12 mm long; the alternative form, var. dunense (Druce) Druce, has stems only 6 cm tall, densely branched from the base and bears short, 2-5 mm, elliptical leaves. Var. dunense is a coastal sand dune form, probably widespread around the shores of B & I, but not yet widely recorded (Sell & Murrell 2009).
Fermanagh occurrence
L. catharticum is frequent to common in Fermanagh, having been recorded in 194 tetrads, 36.7% of those in the VC. As the tetrad map shows, the species is widely but very unequally distributed in Fermanagh. Fairy Flax is very much more often found on the limestone pastures, rocks, cliffs and quarries lying to the W of Lough Erne, where it may be locally abundant in soils that do not completely dry out in summer.
Ecology, established strategy and phenology
Being a very small biennial plant, often flowering when stems are only a few cm tall and seldom exceeding 15 cm in height, L. catharticum must avoid competition in order to survive amongst other plants. It has adopted, therefore, the life strategy of a rather slow-growing, but extremely stress-tolerant ruderal (Grime et al. 1988, 2007). Following spring germination, the plant grows in gaps in turf where it is supported and protected by taller vegetation. At the end of the growing season it overwinters as a very small wintergreen individual. In its second spring, the plant pokes up an erect wiry stem through the surrounding vegetation, which then branches and flowers that summer. Like other biennials, after flowering the exhausted plant dies.
Flowering reproduction
Small white flowers, 5-6 mm in diameter, are produced from June to September in an open, well branched cymose inflorescence of c 20 stalked blossoms. Floral parts are in fives. The flowers are pollinated by various insects, or may self-pollinate and fruit capsules are formed from July onwards (Grime et al. 1988, 2007; Sell & Murrell 2009).
Kelly (1984) showed that very small, relatively few-flowered and therefore habitually 'depauperate' species, like L. catharticum and other similar species of infertile soils (eg Erophila verna (Common Whitlowgrass) and Gentianella amarella (Autumn Gentian)) can manage to regulate their seed production in relation to the available resources in a particular season in just the same way that larger plants, including perennials, do. All the species studied that produced small plants managed to adjust the number of their flowers that set seed and the number of seeds produced per fruit to the resources available in the particular environment. The more fruits they formed, the greater the number of seeds per fruit were produced (Kelly 1984).
The Linum fruit capsule can develop up to ten internal segments, each containing a solitary seed. Seeds are shed from July to October. The seeds are small (0.15-0.19 mg) and they have no structures to enhance dispersal by wind or involving animal transport. However, they can persist and accumulate in the soil seed bank, since they possess an annual dormancy cycle controlled by soil temperature, plus a light requirement for germination. Soil disturbance is therefore required to bring buried seed up to the light at the soil surface. Thus seeds almost exclusively germinate in the spring after a cold winter breaks both primary and secondary dormancy (the latter created by high temperatures in early summer). Any form of soil disturbance may assist the germination process in spring or early autumn when soil temperatures are moderate (Milberg 1994).
Fossil history
Fossil seeds and pollen of L. catharticum have been recorded in the British Pleistocene and, as Godwin (1975) points out, apart from one exceptional occurrence in the late Hoxnian (at Gort in Ireland), all the other 24 records come either from glacial stages, or from late Flandrian (Irish Littletonian) sites associated with cultivation. The seed and pollen records from across B & I agree closely with one another and indicate, "the plant has a strong preference for fresh soils and open conditions, together with tolerance of climatic conditions of at least the early and late phases of glacial periods" (Godwin 1975).
British and Irish occurrence
Thanks to its tolerance of a wide range of poor soil habitats, Fairy Flax or Purging Flax is common and very widespread throughout B & I. Population losses due to intensification of agriculture since 1950 are ameliorated to some extent by colonisation of a range of infertile, artificial, open habitats such as quarries and embankments alongside railways and roadsides (Grime et al. 1988, 2007; G.T.D. Wilmore, in: Preston et al. 2002).
European and world occurrence
L. catharticum is widespread in temperate regions of Europe, stretching northwards to Iceland and to 69oN in Fennoscandia. It also reaches eastwards into W Asia. In southern parts of Europe, it is mainly confined to the mountains (Hultén & Fries 1986, Map 1277; Sell & Murrell 2009). It is introduced in eastern N America and New Zealand.
Names and uses: 'Fairy Flax', 'Purging Flax', 'Dwarf Flax' and 'Mountain Flax' are just four of the numerous English common names applied to Linum catharticum, each telling us something about the species, although not always clearly! It is a small plant (fairies are usually imagined as being tiny, if not dwarf) and it regularly grows in mountains and it contains toxic compounds that have strong purgative and emetic medicinal properties (Grieve 1931; Grigson 1955, 1987; Allen & Hatfield 2004). The whole plant, small, wiry and sparsely leaved as it is, was collected in July when in flower, and used fresh or dried (Grieve 1931). In the second and greatly improved edition of Gerard's Herball (1633), Thomas Johnson described how this plant, also known to him as 'Mil-mountain' or 'Mill Mountain' in Hampshire and Somerset, was taken for its somewhat fierce purging effect to cure constipation and was prepared by bruising it and gently cooking it in a pipkin of white wine. It is bitter tasting and had a powerful purgative action described by Quincy (1718) as, "evacuating viscid and watery humours from the most remote lodgements"; it was apparently also recommended to common people for rheumatism and led Quincy to advise its use, "only for very robust strong constitutions" (Allen & Hatfield 2004). Grieve (1931) says, "it is generally taken combined with a carminative [ie a drug that relieves flatulence], such as peppermint". Fairy Flax has also been prescribed by herbalists for catarrhal infections, liver complaints and jaundice and was, "employed with benefit" (Grieve 1931).
Threats
None.