Flax-leaved St John's-wort  (Hypericum linariifolium)

Flax-leaved St John's-wort (also known as toadflax-leaved St John's-wort) has reddish stems (2), and produces bright yellow flowers (4) with red tinges (2).

At present, this species persists in England in east Cornwall and south Devon, as well as in Caernarvonshire in Wales (3). Around 90% of the number of flax-leaved St John's-wort plants in Britain are thought to occur in the Dartmoor National Park (4). This species is endemic to Europe, and occurs outside of Britain in oceanic parts of western Europe, including Portugal, Spain, France, Madeira, and the Channel Islands (3).

Inhabits south-facing coastal cliffs, and inland where it is found in open areas typically dominated by bell heather (Erica cinerea) in steep wooded valleys, growing on thin soils over acid rocks (6).

This perennial species is often short-lived, and can produce huge quantities of seeds, which need bare patches of earth in order to germinate. Flax-leaved St John's-wort can withstand times of high temperature and drought (3).

Scrub growth, particularly of gorse, is known to pose a threat to this species; fire may also cause problems (3). Cross-breeding with trailing St John's-wort (H. humifusum) has been documented, and this may dilute the gene pool of Flax-leaved St John's wort (4).

Plantlife, the wild plant conservation charity, has included flax-leaved St John's-wort in its Back from the Brink Programme (5), and has carried out a national survey of the species (4). At several sites, scrub control and removal has caused this plant to increase in extent (3). Many of the sites in the Dartmoor stronghold are managed by conservation organisations (4).

For more on this species see the Dartmoor Species Action Plan, available at:
http://www.dartmoor-npa.gov.uk/dnp/pubs/bap16.pdf

Information authenticated by Plantlife, the wild plant conservation charity:
http://www.plantlife.org.uk