This monocarpic, dioecious perennial herb is restricted to dry limestone sites, typically occurring in short-grazed, open, species-rich turf on S.-facing slopes. In heavily grazed turf the plant can be perennial until the opportunity arises to flower. Reproduction is by seed. Lowland.
The distribution of this species has not changed since the 1962 Atlas, and the national population appears to be stable. It persists at one alien site in N. Somerset.
European Southern-temperate element.
Light (Ellenberg): 9
Moisture (Ellenberg): 2
Reaction (Ellenberg): 8
Nitrogen (Ellenberg): 1
Salt Tolerance (Ellenberg): 0
January Mean Temperature (Celsius): 4.9
July Mean Temperature (Celsius): 16.4
Annual Precipitation (mm): 889
Count of 10km squares in Great Britain: 6
Count of 10km squares in Ireland: 0
Count of 10km squares in the Channel Isles: 0
Atlas Change Index: 0.12
RDB Species Accounts
Trinia glauca (L.) Dumort. (Apiaceae)
Status in Britain: LOWER RISK - Near Threatened.
Status in Europe: Not threatened.
T. glauca is restricted in Britain to dry stony limestone sites, typically occurring in short, open, grazed turf on south-facing slopes. Characteristic associates include Festuca ovina, Pilosella officinarum, Sanguisorba minor, Thymus polytrichus and a number of annuals and pauciennials including Carlina vulgaris, Centaurium erythraea and Euphrasia nemorosa, together with Homalothecium lutescens and Weissia species. T. glauca occurs in some of its sites with two other rare plants of the western limestones, Helianthemum apenninum and Koeleria vallesiana, but is not restricted to the xeric conditions which those two species require. It is thus frequently also associated with such species as Briza media, Carex flacca, Helictotrichon pratense and Scabiosa columbaria, and occasionally with Aster linosyris and Potentilla neumanniana. In turf closely grazed by rabbits, plants of T. glauca are no more than a few centimetres tall.
This species is unique amongst British Apiaceae in being dioecious (very rarely monoecious). Flowering is in May and June, the creamy-white flowers of the male plants being especially conspicuous. It behaves either as a biennial or a monocarpic perennial. Regeneration from seed is important in maintaining populations, although its discontinuous distribution is in part a reflection of the very exacting conditions needed for the establishment of new plants. Under grazed conditions, the plant can be a perennial, surviving in a vegetative state until the opportunity arises to flower.
T. glauca is currently known only from the Carboniferous limestone in North Somerset and Gloucestershire, and the Devonian limestone in South Devon, occurring in about twenty sites in six hectads. Populations are generally stable, and records from some sites date back more than two centuries. During surveys in 1988-89 (FitzGerald 1990a; Taylor 1990f) the two largest native populations were found at Sand Point, with an estimated 10,000 plants, and at Crook Peak, with similar numbers. It was abundant at several other sites, ranging from hundreds to a few thousand plants. The large population at Goblin Combe, estimated to number over 18,000 plants in 1989, originated from six rooted plants and 40 seeds sown in 1955 (Hope-Simpson 1987). Most of its sites are protected within SSSIs. A few are grazed by sheep or cattle, and in those which are not, rabbits are especially important in maintaining short open turf. In the Avon Gorge, in the absence of grazing, it is the harsh conditions of the rocky south-facing bluffs that enable T. glauca to survive. This species is not immediately threatened, although potential threats to some populations include a reduction in grazing by domestic stock or by rabbits, and excessive trampling by visitors.
T. glauca occurs throughout western, central and southern Europe, extending to south-west Asia. Its stronghold is in southern and central Europe, becoming rare further north and reaching its northern limit in England. It is threatened in Germany.
R. D. Porley
PLANTATT - Attributes of British and Irish plants. (.zip 1455KB) This dataset was compiled and published in 2004, and last updated in November 2008. Download includes an Excel spreadsheet of the attributes, and a PDF explaining the background and nomenclature. Note that the PDF version is the booklet as published, whereas the Excel spreadsheet incorporates subsequent corrections. A hardcopy can be purchased from the Centre for Ecology and Hydrology.