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Vicia sativa L., Common Vetch

Account Summary

Introduction, archaeophyte, doubtful numbers, perhaps occasional, but most probably it has declined to extreme rarity. European southern-temperate, but widely naturalised.

24 May 1992; Northridge, R.H.; N end of Devenish Island, Lower Lough Erne.

May to September.

Growth form and preferred habitats

This robust, annual vetch with its typically bi-coloured (claret and blue) or violet, purple or rarely white pea flowers was probably introduced to Britain by the Romans around 80-130 AD as a fodder legume crop and, for a long period, it was popular with farmers in both B & I for this purpose and as a ploughed in green manure to enrich soil fertility (Hollings & Stace 1978). Like other vetches, it is not highly specialised in its substrate requirements, but it is generally associated with light, sandy or gravelly soils. V. sativa produces fibrous roots with nitrogen-fixing nodules and is capable of growing up to 150 cm tall on supporting vegetation. It persists to a certain extent on field margins, hedgebanks and amongst rough, occasionally-mown, tall grass on roadside verges and on various forms of disturbed waste ground.

Fermanagh occurrence

V. sativa s.l. is occasional and widely scattered in suitable disturbed ground in the Fermanagh lowlands and around 50% of the local records of it were generated during the exhaustive field-by-field scrutiny of the shores of Upper Lough Erne made by the EHS Habitat Survey Team recorders in the late 1980s (see subspecies accounts below).

Variation

In the 1980s, when the Upper Lough survey was being carried out, this very variable plant was referred to as V. sativa subsp. sativa in all the available identification Floras, including An Irish Flora 1977 and Clapham et al. (1962). Studies over the last 40 years have found that the true nature of V. sativa is that of a taxonomically confusing and variable complex or aggregate of at least six or seven subspecies. These taxa include wild types, weedy races and cultivated derivatives (P.W. Ball, in: Flora Europaea 2, Tutin et al. 1968, pp. 129-36; Hollings & Stace 1978; Aarssen et al. 1986). It is important to appreciate the extent of the variation involved, which is such that at the variety and form levels, the number of taxa described for the V. sativa species aggregate or s.l. comprise several hundred! A wide variation in chromosome morphology which underlies and helps to explain this situation has been reported, with cytotypes existing of 2n=10, 12 and 14 chromosomes (Hollings & Stace 1974).

Further taxonomic work has now considerably clarified the variation within V. sativa found in B & I (Hollings & Stace 1978; Sell & Murrell 2009), so that with the recognition of subsp. segetalis (Thuill.) Gaudin, three, rather than two subspecies of V. sativa (ie subsp. sativa and subsp. nigra (L.) Eheh. (the latter = V. angustifolia L., Narrow-leaved Vetch), are now listed in the New Flora of the BI (Stace 1991, 1997 & 2019; H.J. Killick, in: Rich & Jermy 1998, pp. 183-5).

The critical Flora of Great Britain and Ireland 3 takes taxonomic matters further and now describes seven subspecies in these isles (Sell & Murrell 2009). The additional names to the above mentioned being subsp. uncinata (Rouy) P.D. Sell and subsp. bobartii (E. Forst.) P.D. Sell, both of which Stace (2019) together subsumes into (or includes within) subsp. nigra (L.) Ehrls.; subsp. cordata (Wulfen ex Hoppe) Arcang., which Stace (2019) regards as not confirmed for our flora; and subsp. macrocarpa (Moris) Arcang., which Stace (2019) regards as a rare casual only.

Decline in planting vetches for fodder

The enormous decline of arable farming in Fermanagh and across Ireland in general, plus the general ousting of vetches by clovers and other legumes as preferred fodder and green manure crops, has seen the area of subsp. sativa grown by farmers in B & I gradual drop from the early 1890s when it was 216,000 acres [87,400 ha] in England and Wales, to near-rarity by the late 1950s (Killick 1975). This last author also found that even when it was being replenished by regular sowing, subsp. sativa seldom persisted for long and by 1974 it was becoming scarce in Britain.

Buried seed longevity

Measurements or estimates of the period of survival of V. sativa s.l. seed buried in soil listed in the NW European survey indicated a range from transient (less than one year) (eleven studies), to short-term persistent (1-5 years) (seven studies), to more than five years (just two studies) (Thompson et al. 1997).

V. sativa subsp. segetalis was also cultivated for fodder and manure purposes, so it might also have suffered a similar decline, although like subsp. nigra, it may perhaps maintain itself rather better than subsp. sativa does without additions from fresh agricultural sowing.

Transfer of Fermanagh V. sativa records: The New Flora of the BI (1991, 1997, 2010 & 2019) regards subsp. segetalis as the commonest of the three subspecies in B & I and in view of the inadequate identification treatment of this aggregate in An Irish Flora (1977, 1996), RHN and the current author (RSF) believe it is more sensible to transfer all the Fermanagh records with dates between 1980-91 from subsp. sativa to subsp. segetalis (see below), rather than accept them as the former.

This leaves just nine definite records for subsp. sativa in the Fermanagh Flora Database in seven tetrads, all but two of which lie between Enniskillen and Gublusk Bay, on the eastern shore of Lower Lough Erne. Details of the other two records are: roadside between Enniskillen and Lisnarrick at Glenross, 21 May 1994, RHN; and Sand pit at Pubble Bridge, Tempo River, 20 August 1999, RSF & RHN.

Irish occurrence

The Reynolds's 2002 Cat Alien Pl Ir acknowledges this naming problem and it lists a number of 1990s records of subsp. segetalis from 17 of the 40 Irish VCs.