''Hippocrepis comosa'', the horseshoe vetch,
is a species of
perennial
A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also wid ...
flowering plant
Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...
belonging to the genus ''
Hippocrepis'' in the family
Fabaceae.
Description
The overall appearance depends on its habitat: sometimes it forms upright clumps of flowers; at other times, it sends prostrate leafy runners over a wide area; sometimes it distributes itself as single flowers. The flowers are small, yellow or sometimes orange/red (becoming yellow as they mature), and of typical shape for the family
Fabaceae: these appear for a period of two weeks around May..
Propagation
The rate of seed production is variable: relatively low and sometimes negligible seed production. Seedlings remain the predominant method of extending its range. It has a low germination rate in the wild, although this can be improved in nurseries.
Distribution
''Hippocrepis comosa'' is found in the UK, predominantly in the south..
Habitat
''Hippocrepis comosa'' is a calciole (found only on chalk and limestone). It is a hardy plant that survives long periods of cold winters and dry summers years after year. Colonies are not harmed by sheep grazing, and are resistant to moderate trampling; they do not thrive after heavy ploughing or disturbance of the ground. In areas grazed by cattle they disappear, sometimes after several years (depending on grazing intensity.)
Ecology and butterflies
''Hippocrepis comosa'' is the exclusive food plant of the caterpillars of
chalkhill blue
The chalkhill blue (''Lysandra coridon'') is a butterfly in the family Lycaenidae. It is a small butterfly that can be found throughout the Palearctic realm, where it occurs primarily in grasslands rich in chalk. Males have a pale blue colour, wh ...
(''Polyommatus coridon'') and
Adonis blue (''
Polyommatus bellargus'') butterflies.
Hippocrepis comosa
' Populations that support such butterflies occur on longstanding ungrazed meadows, quarries, edges of paths and wasteland; outside of southern England and the Midlands (e.g. the Gower and Yorkshire populations) the climate is unsuitable for the butterflies.
Re-establishment of a colony of ''H. comosa'' is best attempted by planting individual plants: direct sowing has poor rates of success. Even this however offers no guarantee of a permanent colony (within a period as long as 20 years) and even less likelihood that the new plants will be used by significant populations of chalkhill blue butterflies within another 50 years.
References
{{Taxonbar, from=Q158369
comosa
Plants described in 1753
Taxa named by Carl Linnaeus