This site and its content are under development.

Stellaria palustris Ehrh. ex Hoffm., Marsh Stitchwort

Account Summary

Native, occasional and locally frequent. Eurasian boreo-temperate, but also widely naturalised, including eastern N America, Australia and New Zealand.

1884; Barrington, R.M.; Crom Castle Estate.

June to October.

Growth form and preferred habitats

The normally pale, bluish-green or greyish stem and leaves make this a very distinctive locally abundant, rhizomatous, scrambling, patch-forming perennial in Fermanagh. The typical habitat of the species is in nutrient-rich, mesotrophic to eutrophic, wet to moist ground, often winter-flooded and swampy. In Fermanagh, these enriched, wetland conditions are provided in fens, meadows, pastures and scrub, primarily around the larger lakes, but occasionally also by rivers, streams and ditches, especially where they flood. Although in other parts of Britain and Ireland S. palustris is reputed to colonise artificial, man-made, disturbed habitats, eg old flooded peat cuttings, it does not do this anywhere in Fermanagh (P.S. Lusby, in: Preston et al. 2002).

Variation and identification

Apart from the usually distinctive colour of the aerial parts, S. palustris grows up to a height of around 60 cm and has larger flowers than S. graminea (Lesser Stitchwort) and lacks the ciliate bracts and outer sepals of the latter, the only species with which it might possibly be confused. S. graminea also prefers better drained soils than S. palustris.

We are fortunate that the form of S. palustris present in Fermanagh is so very distinctly grey-green (glaucous), when in fact the colour of the species elsewhere is very much more variable. Elsewhere, the aerial shoots can be whitish, or a pure or a yellowish green, making such plants much less immediately recognisable (Jonsell et al. 2001). On finding the green form in Cambridgeshire in 1985, Walters (1986) naturally worried that English field botanists might possibly be overlooking the species, since not only does it look grass-like when non-flowering, but it may also display a very much later flowering period than the glaucous or pale greyish form, sometimes indeed still being in bloom in early September.

In the critical Flora Nordica of Finland and Scandinavia (Jonsell et al. 2001, pp. 122-5), no less than six variant forms or 'entities' are discriminated within S. palustris, although they can only be identified on combinations of several characters, some of which are relative. The entities are also linked by intermediates, further complicating their identification. It appears that we are dealing with a polyploid complex with exceptionally high chromosome numbers: the series ranges from 10-ploid (2n = 130) up to a 14-ploid with 2n = 182. Little or nothing is known as to how this genetic makeup relates to the six morphological forms, or how much of the observed variation is environmentally induced.

Reproduction

It appears that partial or complete male sterility is common in this species, and unsurprisingly therefore, seed set is poor. Male sterility adds a third level to the variation within the species, as it is expressed both as floral and vegetative dwarfism (Jonsell et al. 2001). In Britain, the average number of seeds per capsule is as low as 13, and the plant does not usually bear many fruits in any case, making its seed output very small (Salisbury 1942, p. 170). Increase in population numbers and local dispersal of S. palustris are clearly very much more dependent on vegetative reproduction than is usual in this genus. Both these aims are achieved by vegetative growth of the slender creeping rhizome, layering of decumbent stem branches, plus stem fragmentation and flotation during floods.

Fermanagh occurrence

In Fermanagh, Marsh Stitchwort has been recorded from 73 tetrads, 13.8% of those in the VC. Nine of the squares have no post-1975 records, indicating a definite decline. Locally, it occupies a decidedly restricted habitat of open areas in winter-flooded marshy grassland, or in base- or lime-rich fens, which in Fermanagh are chiefly found around Upper Lough Erne and along the River Finn. As the distribution map indicates, Marsh Stitchwort has additionally been found – although very much more rarely – on the shores of Lower Lough Erne and in a few scattered additional sites. However, at several of the outlying stations recorded in the 1950s or earlier, it seems to have disappeared, as there are no post-1975 records for them.

British and Irish occurrence

Fermanagh, and in particular Upper Lough Erne, is the northern Irish 'headquarters' of Marsh Stitchwort. Elsewhere in the nine-county province of Ulster there are just three very isolated stations for the plant in VCs E Donegal, Tyrone and Down (H34, H36 and H38) (NI Vascular Plant Database). Apart from this, S. palustris has declined to a certain extent elsewhere in Ireland following a trend in wetland habitat losses that dates back to about the 1940s (Walters 1986; P.S. Lusby, in: Preston et al. 2002). In Ireland, Marsh Stitchwort is now thinly and widely scattered around wetlands in the Central Plain, mainly alongside the long, slow-flowing River Shannon and by numerous tributaries and lakelets off it. Visual inspection of the hectad map for Ireland in the New Atlas indicates that, apart from the four northern VCs already mentioned, it is found in an additional 17 VCs in the Republic.

In Britain the distribution of Marsh Stitchwort is widespread but distinctly thin and patchy, reaching as far north as Perthshire (VCs 87 & 88). The main areas in England are the Norfolk Broads and the Somerset Levels (Walker et al. 2017). The New Atlas map symbols show that there has been a widespread decline in Britain, especially noticeable in lowland areas of C & E England. The decline dates from before the 1930s and represents more than 30% at the hectad level of discrimination (P.S. Lusby, in: Preston et al. 2002). Surviving populations are now small, having a mean of 17 individuals, even in protected sites (Walker et al. 2017).

Reasons for the decline of this wetland species must begin with land drainage, which has undoubtedly occurred on a widespread basis and given rise to loss of suitable, open, wetland habitat. However, other changes in land use and farming are also significant and cause losses, including under-grazing and eutrophication, which together allow invasion and subsequent dominance by tall, vigorous herbs and grasses that out-compete S. palustris and quickly replace it.

European and world occurrence

S. palustris is a Eurasian boreo-temperate species and has a widespread distribution in northern parts of Europe and W & C Asia. It extends south as far as the Alps and the Carpathians, but south of these mountain ranges it is very uncommon. In France, it is mainly confined to the N coast, and is only very thinly scattered elsewhere in the country. It is considered 'endangered' or 'critically endangered' in many French Departments. The species is likewise considered endangered in Switzerland, Belgium, the Czech Republic, Hungary, Germany and Norway. In Great Britain, it is regarded as 'vulnerable' (Walker et al. 2017). In SW Europe, S. palustris is absent from Spain, most of Italy and all of the Mediterranean islands except Corsica (Hultén & Fries 1986, Map 729).

One of the most curious and surprising features relating to the distribution of S. palustris is the fact that the species has been introduced to several regions of the globe, far beyond its native, core area of occurrence. Since it is not a commercial, edible, medicinal or garden plant, it seems rather inexplicable that S. palustris has been introduced and recorded from eastern Canada, Australia, Tasmania and New Zealand (Hultén & Fries 1986, Map 729). However, the authors of the Flora of New Zealand 4 (Webb et al. 1988), rejected S. palustris as not being part of the naturalised flora. One suggestion as to how S. palustris might have travelled across the world's oceans, is as part of ships' ballast. The fact that some strains of the species can grow on seashores suggests the possibility that seed, or other plant parts, might have been incidentally transported in this manner along with shingle, and somehow remained viable until deposited again on a farther shore.

Names

The genus name 'Stellaria' is of medieval origin from the Latin 'stella', meaning 'a star', referring to the shape of the five-petalled flower (Gilbert-Carter 1964). The Latin specific epithet 'palustris' is from 'palus' and 'ŭdis', meaning a swamp of bog, a reference to the typical habitat (Gilbert-Carter 1964). The English common name 'Marsh Stitchwort' is a typical, recent, invented, book name of no folklore significance. The 'Stitchwort' part of the name is examined in my Stellaria holostea species account on this website.

Threats

Habitat loss due to drainage is the principal threat, usually associated with agricultural 'improvement', nutrient enrichment, inadequate grazing, neglect, or general building development. Management using suitable cattle breeds or cutting for hay or haylage is often problematic and uneconomic, due to the small size of many fragmented sites. Sites that are regularly flooded may also require improvement in poor water quality and reduction of cultural eutrophication (Walker et al. 2017).