Source: https://www.brc.ac.uk/plantatlas/plant/Viola-canina-subsp-montana
Timestamp: 2019-04-21 07:35:33+00:00

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A perennial herb of open, moist, peaty ground in fens and on their margins. Reproduction is by seed, which may lie dormant for many years, germinating in response to disturbance which opens up the habitat and reduces competition. Lowland.
Subsp. montana was exterminated before 1930 from some East Anglian sites as a result of habitat destruction. Extant sites at Wicken Fen and Woodwalton Fen (Cambs.) have statutory protection. Morphologically similar plants occur in W. Ireland, but their taxonomic status is uncertain (Webb & Scannell, 1983).
Eurosiberian Boreo-temperate element, with a continental distribution in W. Europe.
This rare subspecies of the widespread but local V. canina, differs from the typical ssp. canina in being much taller, with suberect leafy stems to 30 cm and large stipules up to more than 1 cm long. In habit the plant resembles V. persicifolia, but has more triangular-cordate leaves which are thicker in texture, and no wide-creeping underground rhizome. The pale milky-white colour of the open flower of V. persicifolia contrasts strongly with the blue of V. canina, and the hybrid between these two species (V. x ritschliana) has an intermediate pale colour.
V. canina ssp. montana is confined, so far as is known, to Cambridgeshire, occurring in the NNRs of Wicken, Woodwalton and Holme Fens. Earlier records suggest that the plant was formerly more widespread in that county, and it was recorded at Lakenheath Poor's Fen in West Suffolk in 1954 (S.M.Walters, pers. obs.).
There is some difficulty in assessing the V. canina subspecies involved where rough grazed pasture or heath grades into fen. Thus at Otmoor, Oxfordshire, a survey of ground suitable for V. persicifolia (last seen there in 1963-4) carried out in 1993 revealed only the sterile hybrid V. x ritschliana (V. canina x V. persicifolia) in the absence of both parents. At several Cambridgeshire sites herbarium specimens, referable to one or other subspecies, confirm that V. canina was once more widespread, and usually occurred at the edge of fen areas where V. persicifolia also grew and with which it hybridised.
Hybridisation between V. persicifolia and V. canina was very obvious at Woodwalton Fen, apparently from the early days of the Nature Reserve until at least 1965. The author's own knowledge of the Fen is mainly based on the period 1945-1965, when the south end of the Fen showed a bewildering array of 'fen violets', referable to V. persicifolia, V. canina ssp. montana, and the sterile hybrid. Sterility of interspecific violet crosses is obvious late in the season, because fertile plants set abundant capsules from the cleistogamous flowers produced on the elongated stems after the open flowers, but sterile plants set no fruit. It was these complex violet populations that were described, amongst others, by E.M.Gregory in 1912 in her classic monograph, British Violets.
In continental Europe, where V. canina is more common than in Britain, it is obvious that several tall 'fen-meadow' ecotypic variants occur, and inter-specific taxonomy is more complicated (e.g. Røren, et al. 1994). The use of the name ssp. montana for our fenland plant, based as it is on the Swedish plant that Linnaeus knew, is a practical taxonomic recognition of significant variation, but continental 'montana' has a much wider ecological amplitude than the British plant.
Recent investigations at Wicken Fen, primarily concerning V. persicifolia, have revealed that dormant seed is very important, not only for V. persicifolia but also for the small population of V. canina ssp. montana accompanying it (Rowell, et al. 1982; 1983). Both taxa are clearly dependent upon a combination of disturbance factors in their Wicken and Woodwalton habitats which have the effect of reducing competition and providing open habitats of damp, bare peat for dormant seed germination.

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