Coincya wrightii

Coincya wrightii (O.E.Schulz) Stace (Brassicaceae)

Rhynchosinapis wrightii (O.E.Schulz) Dandy

Lundy cabbage

Status in Britain: VULNERABLE. ENDEMIC. WCA Schedule 8.

C. wrightii occurs only on Lundy, the main centre of distribution being the south-eastern part of the island (Irving 1984; L. Farrell, pers. obs.). It grows in exposed, open communities subject to high atmospheric humidity during the cooler months and great heat coupled with a high light intensity during the summer (Marren 1971). Habitats are mainly the steep or vertical cliffs of granite and slate, but it also occurs on flat ground above the cliff-slopes where protected from grazing animals. It grows mainly in rather open communities where competitors are few. Species which occur in the same habitat include Arrhenatherum elatius, Digitalis purpurea, Holcus lanatus, Lonicera periclymenum, Pteridium aquilinum, Rubus fruticosus, Sedum anglicum, Teucrium scorodonia and Umbilicus rupestris. However, both seedlings and more mature plants can survive in quite closed swards, in deep bracken litter, and under heavy canopies of bramble, gorse or bracken (R.Key, in litt.). 

C. wrightii is a biennial or perennial of variable habit, sometimes tall and straggly, sometimes large and bushy, and dwarf in very dry soil. Populations fluctuate markedly, and in recent years, numbers have ranged from about 320 in 1979 (Cassidi 1980) to 4,500 in 1994. The reasons for the recent increase are not clear, though it is quite possible that a series of warm and dry summers and intervening mild winters in the 1990s favoured the plant.

However, both overgrazing and spread of invasive shrubs are threatening some colonies. Young plants in particular are grazed by domestic animals (sheep and ponies), as well as by rabbits, Sika deer and the free-roaming Soay sheep. Pteridium aquilinum and Rhododendron ponticum locally threaten some colonies. Although there has been substantial control of the invasive shrubs under a Countryside Stewardship agreement, clearance has not so far been concentrated in areas where C. wrightii chiefly occurs.

Invertebrates associated with C. wrightii are of interest, particularly an endemic flea beetle Psylloides luridipennis which is specific to the plant. The biology of the genus Coincya is described in Leadley & Heywood (1990).

L. Farrell and M. J. Wigginton