Viola persicifolia Schreb. (= V. stagnina
Kit. ex Schult.), Fen Violet
Account Summary
Native, very rare, declining and possibly locally extinct. Eurosiberian temperate.
June 1919; Steele, Rev. W.B.; Fardrum Green Loughs, NW of Enniskillen.
May to July.
Growth form and preferred habitats
This small, creeping, perennial is one of the rarest and most vulnerable species in Fermanagh. It is a plant of seasonally wet, base-rich soils in fens and unimproved water meadows on lake shores overlying fen peat. It avoids permanently wet or waterlogged ground. It is a Red Data Book species in both Ireland and England (Irish Red Data Book; Wiggington 1999). It is so very rarely found that we fear it is teetering on the verge of local extinction, at least at its oldest station in Fermanagh – the Fardrum turloughs or 'Green Lakes'. As far as we are aware, V. persicifolia has not been seen at any of our local turloughs since 1992. On a visit in 2004, albeit at the end of August, one of the Fardrum turloughs visited was completely covered in tall, rank grassy vegetation, which leaves no physical or ecological space for a weakly competitive, low-growing herb like V. persicifolia.
Fermanagh occurrence
There are a total of 15 records for the species in the Fermanagh Flora Database, nine of which date between 1919 and 1957. The species tetrad map shows that apart from their date range (six are pre-1975 and four of more recent date), the record distribution falls into two groups. These comprise the original stations at the Fardrum turloughs, near Lower Lough Erne, and secondly, and considerably more widespread, at nine sites on rocky limestone grasslands around the middle section of Upper Lough Erne, an area subject to seasonal flooding. The site names and record dates around Upper Lough Erne are as follows: Inish Rath Island, 1953; Gubdarragh on the southern extremity of the Corrard peninsula, 1953 & 1954; promontory ENE of Tiraroe Jetty, 1953; Coolbeg Td, 1954; Corraslough Point, 19 July 1957; Inishroosk, 21 June 1985; Inishbeg shore, Corrard peninsula, 27 July 1986; Aghinish Island, 16 June 1987; Trannish Island, 16 June 1987. Most of the 1950s records were made by MCM & D (Revised Typescript Flora) and the more recent records by members of the EHS Habitat Survey Team.
At the series of turloughs in the townland of Fardrum, Steele (1919) described the plant as occurring, "in great profusion around the edges of the little loughs", but on a revisit 28 years later in 1947 he found it, "very sparingly". Richard Weyl rediscovered the species at the Fardrum site in June 1985 and RHN recorded it again there on 30 May 1992.
English occurrence
Populations of Fen Violet in Cambridgeshire consistently observed for many years have shown that seed of the species is long persistent. The plant reappeared at sites following vegetation clearance and soil disturbance after periods of five decades of apparent absence (Rowell et al. 1982; Rowell 1983). Studies in England also indicate a strong natural cyclical tendency in terms of violet population numbers (Croft 2000).
In England, V. persicifolia was previously known from more than 20 sites in fens and river valleys, mostly in SE England, but nowadays it seems to have been lost from Norfolk (VCs 27, 28), Suffolk (VCs 25, 26), Yorkshire (VCs 61-65), Lincolnshire (VCs 53, 54) and Nottinghamshire (VCs 56). By the early 1990s its only surviving sites appeared to be in Huntingdonshire at Woodwalten Fen (VC 31) and in Cambridgeshire at Wicken Fen (VC 29), but since 1997 it has revived at another site, Otmoor in Oxfordshire (VC 23), where after decades of apparent absence, it is now the strongest English population (Porter & Foley 2017).
European and world occurrence
In Europe, Fen Violet is widely distributed in cool temperate regions from southern Scandinavia to N Spain and eastwards to W Russia. It is absent from the hotter and drier regions including the Mediterranean basin and the south-east. Its distribution in Asia is local and is only poorly known as it becomes confused with V. pumila Chaix (Hultén & Fries 1986, Map 1329).
Threats
Excessive nutrient enrichment and/or inappropriate drainage or disturbance (either too little or too much) may destroy suitable habitat or encourage aggressive competitors.