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Vicia cracca L., Tufted Vetch

Account Summary

Native, common. Eurasian boreo-temperate, but naturalised in N America and thus now circumpolar.

1881; Stewart, S.A.; Co Fermanagh.

April to November.

Growth form and preferred habitats

This climbing, trailing and twining, tangled, web- or curtain-forming perennial with its very beautifully decorative, many-flowered, bright blue-mauve, one-sided, spike-like raceme of 10-30 pea flowers on a long peduncle and pinnate leaves each with 5-15 pairs of ± parallel-sided leaflets and a branched tendril is unmistakable, at least in Ireland. The base of the plant is a perennial rootstock or a short rhizome (depending on which reference you consult) from which arise both a branched, annual, aerial stem up to 200 cm tall, plus spreading mycorrhizal roots with nitrogen-fixing nodules in the upper soil layers (Aarssen et al. 1986; Grime et al. 1988).

V. cracca clambers over tall supporting herbaceous plants in more open areas associated with woods, scrub, cliffs, hedge-banks, walls and fences. It also grows in various rough grassland situations, including marshy or swampy river- and stream-banks, lakeshores, roadsides and waste places. While quite unspecialized in its substrate requirements, V. cracca appears to be most commonly associated with moist, sandy or gravelly soils. A good example of a mesophyte species, it grows best at pH 6.2 and really avoids only extremes of soil moisture, pH reaction and nutrient levels. It is absent from soils below pH 4.5 (Grime et al. 1988).

Tufted Vetch dislikes excessive disturbance (grazing, cutting and cultivation), deep shade, or exposure to strong winds or severe cold (Aarssen et al. 1986). It can tolerate light grazing and, later in the summer, can survive being cut for hay (Duke 1981). In terms of its established strategy, the colonising and competitive ability of V. cracca is rated as intermediate between competitor and C-S-R, which puts it on a par with Lotus pedunculatus (= L. uliginosus). In species rich grassland it becomes stunted and is eventually ousted (Grime et al. 1988).

Variation

There is considerable chromosome and phenotypic variation within what is described as the V. cracca complex, including polyploidy and aneuploidy (ie unusual non-multiples of the basic chromosome number). The common chromosome race in B & I is tetraploid (2n=28), plus there are other races with 2n=14 (diploid), 12, 27 and 30 chromosomes (Aarssen et al. 1986; Grime et al. 1988). Four intraspecific taxa have been recognised and named as varieties in the critical Flora of B & I (Sell & Murrell 2009), as var. cracca, var. leptophylla Fr., var. sericea Peterm. and var. pulchera (Druce) P.D. Sell. They differ in degrees of hairiness, leaflet dimensions and flower colour. Stace (2019) makes no mention of any of these varieties.

Flowering reproduction

From June to August, the very numerous, 8-13 mm long, clear blue-mauve flowers, which are self-incompatible, attract various large bees as pollinators. The vetches (Vicia and Lathyrus) have a secondary pollen presentation reminiscent of that of the brush mechanism of the genus Campanula. The style is bent up sharply from the tip of the ovary and carries a dense brush of fine hairs just below the stigma. The anthers open and release their pollen while the flower is still in bud and the pollen is shed on to the tip of the brush or into the tip of the corolla keel where the brush sweeps it out as the keel is depressed. By the time the flower opens the anthers have retracted but the stigma brush is fully charged with pollen as it comes up into contact with the lower abdomen of a visiting bee.

The petals are relatively large and stiff and an insect has to be weighty, powerful and long-tongued in order to penetrate the stamen tube and reach the concealed nectar. The flowers are, therefore, more or less restricted to bumble-bees, although other insects may steal the nectar by biting into the base of the flower and circumventing the designed mechanism (Proctor & Yeo 1973).

Later in the season (mainly August to September), the dry, mature, 10-25 mm, legume pod splits suddenly at maturity, explosively hurling out 2-6 relatively large, hard, reddish-brown seeds a short distance. Birds and grazing animals may also eat the legume and eventually pass the intact seeds with their faeces, achieving long distance dispersal (Aarssen et al. 1986; Grime et al. 1988).

Vegetative reproduction

Shallow spreading roots assist the plant to reproduce by vegetative means: buds on the roots can give rise to new adventitious aerial shoots at intervals. Typically, V. cracca forms quite small clonal patches in grasslands, indicating that this form of reproduction is not very significant or particularly successful. The main method of increase is through seed production and dispersal.

Fermanagh occurrence

V. cracca is not quite as common and widespread in Fermanagh as the much less showy V. sepium (Bush Vetch). Yet with records in 310 tetrads, 58.7% of those in the VC, V. cracca remains a very familiar and widespread vetch in lowland Fermanagh.

British and Irish occurrence

The undemanding habitat requirements mean that V. cracca is very common and widespread throughout B & I, scarce only in the Scottish Highlands and the wet, peaty NW of Britain (New Atlas).

European and world occurrence

Rather variable and partly spread by human activities including farming and trade in seed and fodder, V. cracca s.l. (including in more southern areas V. tenuifolia Roth (= V. cracca subsp. tenuifolia (Roth) Gaudin)) is widespread throughout most of Europe plus Greenland, and Asia to Sakhalin and Japan. It is introduced in N America, S Africa, Tasmania and New Zealand and is now circumpolar boreo-temperate (Hultén & Fries 1986, Map 1200; Sell & Murrell 2009).

Threats

None.