Northern Ireland's Priority Species

Viola persicifolia – fen violet

 

Distribution map

Click here to view an interactive map of the Northern Ireland dataset as currently collated by CEDaR.
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Viola persicifolia Schreber
Family: Violaceae

This small creeping perennial (sometimes also referred to as Viola stagnina Kit.) is one of the rarest and most endangered species in these islands. It is a Red Data Book species in both Britain and Ireland, listed for protection throughout these islands on account of its major decline over many years to current extreme rarity (Curtis and McGough, 1988; Wiggington, 1999). In Ireland fen violet occupies the habitat of 'vanishing lakes' or turloughs. These are winter-flooded hollows, usually of shallow slope in limestone districts, where the vegetation varies between more or less grassy summer pasture and almost bare rocky 'pavement'.

In brief

  • In Northern Ireland, fen violet is confined to rocky limestone lake shores of Upper Lough Erne and to turloughs or vanishing lakes around Fardrum, but it has not been seen since 1992

  • Fen violet inhabits winter-wet habitats such as fens and short calcareous grasslands where occasional grazing or disturbance keeps bare ground available for seed germination

  • Fen violet is a short-lived perennial which begins to flower in May

  • This species is rare with Northern Ireland being the UK stronghold

  • Threeatened by competition of taller-growing vegetation, and agricultural improvement.

Species description
Certainly the most beautiful of all our native violets, the fragile-looking flowers are a pale, bluish-white in colour and they usually have a sheen reminiscent of mother-of-pearl. The flowers are almost circular in full-face profile and are around 10mm in diameter. The flower also has a short, greenish spur. The plant has no basal leaf rosette and the leaves are ovate-lanceolate, cut off abruptly, or somewhat notched at the base – rather reminiscent of a teaspoon in shape.

Life cycle
Seeds germinate in spring on bare patches of peaty soil above the water table, but the violet only establishes new plants if the water table drops and the soil surface becomes drier. Normal open flowers appear in May, followed by small closed bud-like ones from June onwards. The latter 'cleistogamous' flowers self-pollinate in the bud the technical term means 'closed marriage'. Both flower types produce around 18 seeds per capsule, the selfed flower production being more reliable. Seed is squeezed out of the drying valves of the fruit capsule after it splits, but dispersal distances are normally measured in centimetres and juvenile plants develop close to the parent plant. Some seed may be carried further in mud adhering to passing animals. Seed appears perfectly capable of dormant survival buried in damp or wet ground for many years. The history of population resilience and re-emergence after periods of apparent absence (that is, no reported sightings), lasting sixty or more years in English fens has been well documented (Woodell, 1965; Rowell, 1984). It is possible that levels of habitat disturbance which encourage seedling development may simultaneously destroy established stolon-producing plants, or limit their growth (Pullin and Woodell, 1987; Croft, 2000). Populations tend to fluctuate rapidly and widely in numbers, perhaps in a vaguely cyclical manner.

Similar species
While a rare and unusual plant, it is actually very easy to confuse fen violet with the common dog-violet, Viola riviniana. In addition, fen violet sometimes associates with Viola canina, heath dog-violet, and the two species frequently form intermediate hybrids which confuse their positive identification.

How to see this species
Fen violet inhabits winter-wet habitats such as fens and short calcareous grasslands where occasional grazing or disturbance keeps bare ground available for seed germination. It is a short-lived perennial which begins to flower in May. Relevant access permissions should always be sought prior to visiting any sites.

Current status
In Northern Ireland, fen violet is confined to rocky limestone lake shores of Upper Lough Erne and to turloughs or vanishing lakes around Fardrum. It has not been seen since 1992. In the Republic of Ireland its distribution is restricted to turloughs in north Clare and south Galway. It grows near the low water mark of turloughs. It is distributed widely, but thinly, through middle latitudes of temperate Europe from southern Scandinavia to northern Spain, and eastwards to Russia and parts of Asia. It has become rare or extinct throughout Western Europe along with the loss of its typical base-rich fen peat habitats, following their drainage or overgrowth.

Why is this species a priority in Northern Ireland?

  • This species is rare with Northern Ireland being the UK stronghold.

Threats/Causes of decline
Habitat loss is the major problem this species faces. In Ireland, the turloughs may become overgrown by taller-growing vegetation, or the grassland may undergo agricultural improvement. Drainage operations and inappropriate management of fenland sites have contributed to the decline of fen violet in England.

Conservation of this species

Current action

  • Seed has been collected for preservation and cultivation at the National Botanic Gardens, Glasnevin, Dublin

  • One of the sites for this species, in Fermanagh, Fardrum and Roosky Turloughs, is under ASSI designation.

Proposed objectives/actions

  • Maintain the number of viable populations of the species.

What you can do

Further information

Links
Flora of Northern Ireland

http://www.ehsni.gov.uk/area_interest_sitesview?SiteNo=ASSI138

Literature
Croft, J. (2000). Fen Violet Viola persicifolia at Wicken Fen: a reinforcement population. Nature in Cambridgeshire 42: 27-33.

Curtis and McGough (1988). The Irish Red Data Book: 1. Vascular Plants. Wildlife Service Ireland. Stationary Office, Dublin.

Grime, J.P. (1979). Plant Strategies and Vegetation Processes. John Wiley & Sons., Chichester.

Hölzel, N. (2003). Re-assessing the ecology of rare flood-meadow violets (Viola elatior, V. pumila and V. persicifolia) with large phytosociological data sets. Folia Geobotanica 38(3): 281-297.

Pullin, A.S. and Woodell, S.R.J. (1987). Response of the Fen Violet, Viola persicifolia Schreber, to Differential Management Regimes at Woodwalten Fen National Nature Reserve, Cambridgeshire, England. Biological Conservation 41: 203-217.

Rowell, T.A. (1984). Further discoveries of the Fen Violet (Viola persicifolia Schreber) at Wicken Fen, Cambridgeshire. Watsonia 15: 122-123.

Wiggington, M.J. (1999). British Red Data Books 1. Vascular Plants. Joint Nature Conservation Committee, Peterborough.

Woodell, S.R.J. (1965). Viola stagnina in Oxfordshire. Proceedings of the Botanical Society of the British Isles 6: 32-36.

Text written by:
Dr Ralph Forbes