Callitriche stagnalis Scop. s.s., Common Water-starwort

Account Summary

Fermanagh occurrence

As the New Atlas map indicates, this is the most common species of Callitriche in B & I generally and this is also the case in Fermanagh. It is also regarded as being the most common, widespread and locally abundant member of the genus in Europe, and can occur in a very wide range of wet to damp habitats, but it occurs less frequently in deep or fast-flowing water, than in still or slow-flowing water (Lansdown 2008). C. stagnalis has been recorded in 113 tetrads, 21.4% of those in the VC. As the Fermanagh tetrad map shows, Common Water-starwort is widely distributed over the whole of the area, but it appears somewhat more frequently around Upper Lough Erne. As usual, however, it is important to remember and recognise that thanks to the NI Lake Survey, Upper Lough Erne has been more extensively surveyed in comparison with the remainder of the county.

Preferred habitats

C. stagnalis occurs as a shallow, floating and submerged water aquatic over the whole range of nutrient status from oligotrophic to eutrophic, avoiding only the most acidic, nutrient-starved peaty pools, but including seasonally flooded basins like Roosky turlough. It frequently also behaves as a terrestrial annual of seasonally flooded or regularly damp ground, both in shade and in more open situations. This behaviour appears to be especially the case the further west one goes in B & I (Preston & Croft 1997). C. stagnalis generally occurs with a mixture of terrestrial and amphibious species, such as Agrostis stolonifera (Creeping Bent), Apium nodiflorum (Fool’s-water-cress), Epilobium hirsutum (Great Willowherb), Juncus articulatus (Jointed Rush), J. bulbosus (Bulbous Rush) and J. effusus (Soft-rush). It rarely occurs along with truly aquatic plant species, but it frequently co-habits with Callitriche palustris (Narrow-fruited Water-starwort) and C. brutia var. brutia (Pedunculate Water-starwort) in ephemeral wetlands and on the exposed muddy margins of lakes and pools with fluctuating water levels (Lansdown 2008).

Local examples of terrestrial habitats of C. stagnalis occur in ephemeral pools in damp lakeshore woods, such as Reilly Wood and Silles Wood, but it has been recorded also in the much more upland valley wood of the Correl Glen NR, plus on steep sloping wooded scarps at Pollaphuca (also known as 'Poulaphouca') and Hanging Rock NR. It has been found in the marsh beside Doagh Lough, in hollows and ruts in Lackboy meadows and on Skreen Hill, Derrin Mountain and Legacurragh above Florencecourt. The latter represents more calcareous terrain than would be normal for this species, but the ground is overlain in places by fairly shallow, somewhat disturbed peaty soil. C. stagnalis has also been rarely recorded in ditches along roadsides.

British and Irish occurrence

Lansdown (2008) warns that while C. stagnalis is recorded as widespread and locally abundant throughout B & I, it is probably over-recorded for C. platycarpa (Various-leaved Water-starwort) as the two are not easily and reliably separable, the only really definite distinction involving the uniformly spherical pollen grains of C. stagnalis. In addition, Preston & Croft (1997) suggest that at least in SE England some records of C. stagnalis may perhaps be referable to C. obtusangula (Blunt-fruited Water-starwort).

European and world occurrence

C. stagnalis s.s. occurs throughout Europe from the Azores to Iceland and east to Belarus and W Russia. It is an introduced alien in N America, Australia, New Caledonia and New Zealand (Lansdown 2008).

Threats

Probably none, but insufficient accurate data to be certain.

• Find out more about the format of the species accounts
• View abbreviations
• View references for all species accounts
• View a gazetteer of all the sites