Anthyllis vulneraria L., Kidney Vetch

Account Summary

Growth form and preferred habitats

This typically pale-yellow flowered, but extremely variable, polymorphic, creeping, decumbent or erect, usually perennial legume with a stout rootstock has lower leaves pinnate, often with a large terminal and 4-7 pairs of usually smaller lateral leaflets without tendrils. It is a characteristic indicator species of calcareous, shallow, dry, rendzina soils of chalk and limestone grassland vegetation across B & I. As many as 24 subspecies are recognised in W Europe and five of them, plus several varieties, are recognised as occurring in B & I (Cullen 1986; Stace 2019). Only three of the five subspecies in B & I are considered native. Subsp. vulneraria is one of these natives and chiefly frequents open, dry, usually calcareous grassland, including on waste ground, and at the coast on sand dunes, in rock crevices and on cliff ledges and maritime heaths. The coastal form of this subspecies is sometimes referred to as var. langei Jalas. A more mountain-based form of much more restricted distribution in B & I is subsp. lapponica (Hyl.) Jalas.

Fermanagh occurrence

A. vulneraria is a more important member of Fermanagh's plant community than might first appear. It has been recorded in 27 tetrads (5.1% of the total), spread largely across warm, well-drained, sloping limestone pastures, rock outcrops and south-facing screes to the W of Lough Erne.

At Monawilkin, on limestones of the Western Plateau, it is the essential, specific food-plant of the monophagous caterpillars of the only colony of Small Blue butterflies surviving anywhere in NI. A. vulneraria is also the principal larval food-plant of the much more common and very familiar Six-spot Burnet Moth. The only Fermanagh colonies of this insect are again found on the Monawilkin and Knockmore limestones (Thompson & Nelson 2006).

Flowering reproduction

Kidney Vetch flowers from June to September. The inflorescence is a dense cyme of around 18 flowers, up to 4 cm in diameter. Flower-heads are often paired and have twin, leafy, finger-like bracts at their base. The twin flower-heads are carried on a single, long stalk or peduncle. Flower colour is very variable, but with us they are usually pale yellow, or rarely reddish. Apart from the interesting butterfly and the day-flying moth mentioned above, various bees visit the plant to feed on pollen and nectar and collect these for their brood. Only larger bees with a long proboscis are sufficiently heavy to effect successful pollination. Nectar theft is common however, short-tongued bees biting through the calyx and corolla near the base to steal from the flower.

Unlike many other pea-flowers, the two keel petals do not separate to expose the style and stamens when the keel is depressed by the weight of a visitor. First the pollen and, subsequently, the stigma are squeezed like tooth-paste through a tiny opening at the tip of the fused keel petals of the corolla, depositing and later collecting pollen grains transferred on the hairy abdomen of the visiting bees (Proctor & Yeo 1973).

The single- or two-seeded, dry, indehiscent legume fruit pod is surrounded by the persistent inflated, densely white-hairy calyx. Eventually the dry, brown flower-heads become detached and are wind-dispersed, representing a good example of a tumbleweed (Cullen 1986; Knight 1997). Seed germination is delayed by the indehiscent fruit pod, but probably the species population of the following year benefits most from overwintering seedlings initiated in autumn, rather than from slower developing plantlets from spring germination (Knight 1997). Work is required to clarify this matter.

Population biology

Field populations of coastal and inland plants were studied in the Netherlands for several years by Sterk (1975). This showed that seeds germinated predominantly in the spring and seedlings grew on but did not flower until their second spring at the earliest. There was a period of high seedling mortality in both inland and coastal populations, and plants took longer to reach flowering capability, and fewer plants managed to flower, and each produced fewer flowers in the inland populations compared with coastal plants. The more open, less competitive vegetation in coastal dune grassland conditions allowed more appreciable annual fluctuations in population density and in biomass production of generative individuals than in inland calcicole grassland populations on a loam soil. Coastal plants flowered earlier, more frequently and were more seed productive than the inland populations.

Generally, the seed production per plant in A. vulneraria is low, each flower producing only a single seed (or very rarely two seeds). In favourable years, coastal plants produced a mean of 20 flower heads, of which usually 13 were seed-forming, thus averaging 260 seeds per plant. Plants of the inland population in favourable years formed 4-5 heads, with ten productive flowers, producing around 50 seeds per individual. Predation and parasitism by a number of beetles, moths and gall midges reduced the number of viable seed produced per m² (Sterk et al. 1982). However, a small proportion of the inland plants survived longer than coastal plants did, rarely up to four years and very rarely five (Sterk 1975).

In open stands of vegetation along the coast, lack of moisture was a more important cause of mortality, whereas in the denser vegetation inland, biotic factors, especially competition and predation were more important. In unfavourable years, not a single individual attained the generative stage in the coastal populations and local survival in such cases depended on dormant seed present in the soil (Sterk 1975).

British and Irish occurrence

In NI, A. vulneraria is predominantly a common coastal plant of rock crevices and sand and shingle habitats, although a few inland stations on free-draining, base-rich, usually calcareous rocks and soils do exist in all six VCs (H33 and H36-H40).

The New Atlas hectad map shows that Kidney Vetch is much better represented at inland sites on the limestones of the Irish Midlands than it is in inland NI. This is especially so on the bare limestone karst areas of the Burren in Cos Clare (H9) and NE Galway (H17) and along the banks of the great inland River Shannon.

In Britain, the species is very widespread in the lowlands, again principally occurring either at the coast or on inland limestone and on other near-neutral, base-rich soils (Preston et al. 2002).

European and world occurrence

A. vulneraria s.l. is exceedingly polymorphic and is native throughout Europe, stretching east to the Caucasus and south into N Africa and Ethiopia (Hultén & Fries 1986, Map 1252). J. Cullen (1968) in Flora Europaea 2 recognises 24 subspecies and there are numerous additional varieties within these. The subspecies each have rather distinct geographical distributions and some are endemic to restricted areas. Subsp. vulneraria is the typical form in B & I and it stretches across N Europe from Ireland to Finland and Latvia. The coastal form in B & I is referred to as var. langei Jalas and it occurs from B & I to the coasts of the Channel Isles, France, Belgium, the Netherlands, Denmark and Germany (Sell & Murrell 2009). A. vulneraria s.l. has been introduced to several areas in N America and also to New Zealand (Hultén & Fries 1986, Map 1252).

Names and uses

The names Anthyllis vulneraria ('vulnerary' means 'healing of wounds') and Kidney Vetch might certainly point to herbal medicinal usage, but there does seem to be a dearth of information to confirm this in many English literature sources (eg Grieve 1931; Vickery 1995; Allen & Hatfield 2004). The latter says, "Despite a reputation throughout Europe as a vulnerary, the only allegedly folk use traced of Anthyllis vulneraria has been in the Highlands [of Scotland], where, under two Gaelic names, it is said to have been used in the past for cuts and bruises." Darwin (1996), The Scot's Herbal, confirms this, briefly stating, "Kidney vetch was used to treat wounds and also was added to hay." Vickery (1995) mentions that on the Channel Islands the leaves were used to check bleeding from wounds.

The most detailed herbal medicinal account found is Launert (1981) who describes the plant as an ancient remedy for eruptions of the skin, slow-healing wounds, minor burns, cuts and bruises. A decoction could either be added to bathwater or applied as a compress, or sometimes the bruised fresh herb was applied to the affected area. A mild infusion could be taken against constipation or drunk as a spring tonic. The dried flower-heads might also be used as a substitute for real tea.

The genus name 'Anthyllis' is from the Greek 'anthos' meaning 'a flower' and 'ioulos' meaning 'down' or 'downy', an obvious reference to the downy calyx (Johnson & Smith 1946).

Grigson (1955, 1987) lists no less than 20 English common names for the plant, many of them shared with or borrowed from Lotus corniculatus. The much smaller pods of A. vulneraria make the application of some of the names involving feet, fingers, thumbs or claws much less than appropriate in this instance, although the reference might be to the paired, finger-like bracts beneath the twin inflorescences.

Threats

'Improvement' or disturbance of limestone pastures.

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