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Portrait of Kidney vetch

Nature · Wildflowers & flowers

Kidney vetch

Native · flowers Jun–Sep · sand dunes, chalk grassland and sea cliffs

Anthyllis vulneraria — Fabaceae

Kidney vetch is a low, spreading, silky pea-family plant with round clusters of yellow flowers sitting on woolly cushions, found on sand dunes, chalk grassland and cliffs. Its great claim to fame is that it is the only food of the caterpillars of the small blue, Britain's smallest butterfly, so where the vetch is lost, the butterfly disappears too. Old herbalists called it woundwort and used it on cuts.

How to spot them

  • ▸Round, tightly packed heads of yellow flowers (sometimes orange or red), each sitting on a woolly, inflated calyx that makes the head look furry
  • ▸Leaves divided into narrow leaflets, silky and silvery-white beneath — turn a leaf over to check
  • ▸Low, sprawling plant to about 30 cm on dunes, cliffs and chalk grassland
  • ▸Flowers June to September
  • ▸Look-alike: horseshoe vetch (yellow, in loose, flat-topped clusters, with horseshoe-shaped pods, on chalk) and common bird's-foot-trefoil (small, reddish-bud flowers on slender stalks). The furry, round heads of this plant are unmistakable

How to know it

Round heads of yellow flowers on woolly, swollen calyces, above silky leaves that are silvery-white on the underside, on a sand dune or chalk slope

Kidney vetch, Anthyllis vulneraria.

The caterpillars of Britain's smallest butterfly eat only the flowerheads of this plant, so the insect can live only where it grows

Kidney vetch is the sole foodplant of the small blue, Cupido minimus.

Old herbalists named it woundwort and used it to treat cuts, the Latin epithet meaning 'of wounds'

Anthyllis vulneraria — from Latin vulnus, wound; the kidney part of the name comes from its use for kidney ailments.

Turn the leaf over: a silky, silvery underside separates this cliff, dune and chalk pea from others with similar yellow flowers

Kidney vetch — Plantlife.

Yellow is usual, but on some coasts the flower heads of this legume are orange or red

Kidney vetch.

A member of the pea family that fixes its own nitrogen, it colonises bare ground on dunes and cliffs and can cover it as a spreading mat

Kidney vetch — Wildlife Trusts.

Quick-fire facts

  • •Native perennial of dunes, sea cliffs and calcareous grassland, flowering June to September (Wildlife Trusts and Plantlife)
  • •Family Fabaceae, the pea family; it fixes nitrogen with root bacteria like clovers and vetches
  • •The small blue butterfly (Cupido minimus) lays eggs on the flowerheads, and the caterpillars feed on the developing seeds; kidney vetch is its sole larval foodplant (Wildlife Trusts)
  • •The small blue's wingspan is 1.8–2.7 cm, making it Britain's smallest butterfly; it is protected under the Wildlife and Countryside Act 1981 (Wildlife Trusts)
  • •Adult small blues nectar on common bird's-foot-trefoil and horseshoe vetch but stay near kidney vetch
  • •Also known as woundwort, and traditionally used by herbalists for swellings, wounds and kidney and digestive complaints (Wildlife Trusts)
  • •Habitats are managed by grazing with traditional breeds, hay-cutting at the right time and scrub clearance
  • •Rated common, but small blue colonies are often tiny, sometimes of only a few dozen butterflies

Drill it — 7 cards

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