Kidney Vetch and the small blue

The kidney vetch Anthyllis vulneraria was noted in  a recent post about nitrogen-fixers living by the shore on the east coast of Angus. But the kidney vetch has wider acclaim as host of the rare Small Blue butterfly Cupido minimus.

Flowering 'head' of kidney vetch (Squire / Living Field)
Flowering ‘head’ of kidney vetch (Squire / Living Field)

The small blue lays its eggs in the flowering heads of kidney vetch. The hatched larvae then eat the flowers and the developing seed.

However, the range of the butterfly in the north east has decreased in recent years and attempts are being made to record its occurrence. For more on the small blue and current surveys in Scotland –

In the latter can be found people to contact if you want to take part in surveys or to report sight of the butterfly.

Kidney vetch

The kidney vetch is one of the nitrogen-fixing legumes that occur in nitrogen-poor, dry and unshaded environments around the coast of eastern Scotland. 

Yet it was once considered as a sown forage – a constituent of vegetation managed for stock-feeding. Lawson and Son (1852) write that it ‘does not yield much produce, but is eaten with avidity by horses, sheep and cattle, and also by hares and rabbits, and might therefore be introduced into mixtures for very dry soils’.

In the Garden

The Living Field garden grows kidney vetch in its medicinals collection and in the raised beds that have housed a legume collection over the past few years (images below). It grows well, forming luxuriant clumps up to 30 cm in height, taller than on the coast. The flowers are usually more yellow, less red than on the wild plants.

It flowers and seeds profusely in the garden. Some plants die in the winter, but in the last two years it has regenerated freely from its own dropped seed.

Kidney vetch, a forage and wound herb, in the Living Field garden (Living Field/Squire)
Kidney vetch, a forage and wound herb, in the Living Field garden (Living Field/Squire)
The flower heads

The round ‘wooly’ heads may be confusing at first sight, but each ball consists of usually three separate heads each holding many individual flowers. The three heads do not all flower at the same time.

In the image at the top of the page, the head to the lower right is the latest to flower – some flowers are still in bud while others have the fresh yellow petals emerging from the red calyx tube (which previously enclosed the bud).  The head to the left has a mix of new and withered flowers. The largest one, at the top middle and right, has finished flowering: all petals are withered orange, the calyx tubes have turned purple and the hairs have expanded into a whitish mass, protecting the seeds that will form deep in the tubes.

Reference

Lawson and Son. 1852. Synopsis of the vegetable products of Scotland. Authors’ private press, Edinburgh.

 

Fixers 1 Coastal legumes

First in a series on nitrogen fixing legume plants.

Legumes are a group of plants that ‘fix’ nitrogen gas from the air to make proteins that are essential for growth and survival. When legume tissue dies, the nitrogen (N) is returned to the soil.

Legumes have many uses to people as food, medicinals and dyes. They also support insects that in turn  carry out ecological functions such as scavenging and pollination.

Here we begin a short series on wild N-fixers. First are those that live by the eastern shores of Angus.

lf_noim_lgmngs_gs_1100

The east coast of Angus (middle image) is rich in wild legumes. Those shown here live just above the beach or on top of the cliffs, where the vegetation is short and there are no bigger plants to out-shade them. Top left is a patch of purple milk-vetch Astragalus danicus and white clover Trifolium repens behind, top right kidney vetch Anthyllis vulneraria with litter, and ( bottom) flowering heads of kidney vetch (left)  and purple milk vetch.

Nearby were patches of meadow vetchling Lathyrus pratensis, bird’s-foot-trefoils Lotus species, and on the cliff-tops bush vetch Vicia septum, gorse or whin Ulex europaeus, broom Cytisus scoparius and the introduced laburnum Laburnum anagyroides.

One reason for the presence of legumes here is an unfarmed  habitat, low in nitrogen. Fixation by the legumes is one of the main routes by which the plants and soils get their essential nitrogen.

Most of these wild legumes have been tried over the last few thousand years as crops or forages. Some such as kidney vetch have been well-know medicinals (a vulnerary is a herb for treating wounds). Few have remained useful to agriculture, perhaps the best known being white clover, still cultivated today to enrich grass fields with fixed nitrogen.

Legumes are of the pea family Fabaceae, previous known as Leguminosae.

Related on this site:

Contact: geoff.squire@hutton.ac.uk