Red hemp-nettle is covered in soft hairs, and has narrow, weakly toothed leaves which occur in opposite pairs on the stem (4). It produces flowers in small whorls on the stem, which are dark red or pinkish in colour with yellow flecks on the lower lip(4).
Formerly widespread throughout lowland England, Wales and eastern Scotland, this plant suffered a severe decline in range after 1930 (5). It is now scarce in Great Britain, and mainly occurs in central southern England (5). This species is considered by some to be a native in some parts of Britain where it occurs in natural habitats such as coastal shingle or limestone screes, and by others as an ancient introduction (5). It is rare in north-western Europe, and also occurs in central, western and southern Europe, reaching east to Bulgaria and Poland (3).
Once a locally common weed of arable land, it is now rarely seen. It occurs on roadsides, tracks, waste ground, spoil heaps, limestone scree and limestone pavements, and occasionally grows on sand and shingle on the coasts of southern England and Wales (3)(5). The species shows a preference for sunny locations with fairly open vegetation and free-draining calcareous soils (3)(5).
Most of the factors affecting this species involve changes in agricultural practices, including the use of chemical herbicides and fertilisers, sowing crops in autumn before red-hemp nettle has a chance to set seed, and the introduction of crops that have very high productivity (3). Some shingle sites are threatened by coastal development (2).
This species is one of 15 arable plants listed on the UK Biodiversity Action Plan priority list (6). The Species Action Plan aims to enhance the current range by restoring populations to eight former sites by 2003, and set up ex-situ facilities, which will provide a source for potential reintroductions and preserve the genetic variation of this species (3).
The UK Biodiversity Action Plan for this species is available at UK BAP.
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