A perennial herb of base-rich substrates. On the North Downs it is usually found in close-grazed chalk grassland, and in N. England in limestone grassland, on rock ledges and in fissures in limestone scars, and sometimes on damp stream banks and in areas of eroded sugar limestone. Generally lowland, but reaching 530 m on Cronkley Fell (N.W. Yorks.).
The overall range of this species has changed little, although it has disappeared from some sites and greatly declined in others, particularly in Kent, during the last few decades. This is probably caused by changes in grazing regimes.
European Boreo-temperate element, with a continental distribution in W. Europe.
Light (Ellenberg): 9
Moisture (Ellenberg): 6
Reaction (Ellenberg): 9
Nitrogen (Ellenberg): 1
Salt Tolerance (Ellenberg): 0
January Mean Temperature (Celsius): 2.8
July Mean Temperature (Celsius): 15
Annual Precipitation (mm): 1037
Count of 10km squares in Great Britain: 18
Count of 10km squares in Ireland: 0
Count of 10km squares in the Channel Isles: 1
Atlas Change Index: -0.1
RDB Species Accounts
Polygala amarella Crantz (Polygalaceae)
P. amara auct., including P. austriaca Crantz
Status in Britain: VULNERABLE.
Status in Europe: Not threatened. Endemic.
An extreme calcicole, P. amarella grows in open sites in short turf overlying calcareous rocks, often on sloping banks where the drainage is good. All its sites in northern England are in areas of heavy rainfall but its habitats are not prone to waterlogging. Where this species occurs in calcareous mires, as near Malham, it grows on tussocks raised above the wetter surrounding areas. It ascends to 530 metres on Cronkley Fell. In southern England, P. amarella favours open chalk grassland in the absence of vigorous competition. Associated species include Carex flacca, C. panicea, Festuca ovina, Helianthemum nummularium, Sanguisorba minor and, in the north of England, Sesleria caerulea. Polygala vulgaris is also often present, and is a potential source of mistaken identity.
It is a small, often prostrate, herbaceous short-lived perennial. Flowering usually begins in May and can continue until mid-July. Seed germinates freely. Variation in P. amarella is discussed in Fearn (1975).
P. amarella occurs in four disjunct areas in England: Kent, the Craven district of Yorkshire, the limestone districts near Orton, Cumbria, and the 'sugar' limestones of Upper Teesdale. Some of the sites have very few plants, but one of the Craven populations may exceed 1,000 plants, and on Widdybank, more than 100 plants were counted in June 1994. Only small populations of fewer than twenty plants occur at some sites. P. amarella seems to have declined markedly in Craven. It was not found at six of the eight sites surveyed in 1994 and 1995, despite prolonged searching. It seems likely that declines and extinctions can be attributed to recent intensification of farming practices, particularly increased stocking rates. Since it is a short-lived species the removal of flowers and fruit by grazing animals could quickly lead to permanent losses.
It may be significant that the two sites where it was found in 1994/5 are ungrazed banks. The Kentish sites suffer the additional threats of urban development, the ploughing up of chalk grassland and, in some cases, inadequate grazing leading to the growth of scrub or coarse grass swards. Since the soils on which P. amarella grows are extremely skeletal with very low humus content, Kentish populations in particular may also be liable to summer drought (F. Rose and J. Pitt, pers. comm.). Most of the northern sites and some of the Kent sites are within nature reserves or SSSIs, but recent records from Kent are incomplete, and need updating as a matter of urgency.
Two distinct species, Polygala amara in the north and P. austriaca in the south, were once differentiated on the basis of morphological differences and geographical location. Most authorities now consider that they are best treated as different races of a single polymorphic species, P. amarella.
P. amarella has a wide distribution in Europe, encompassing discrete populations in the Pyrenees, northern France, the French and Swiss Alps, central and eastern Europe and Scandinavia.
M. S. Porter
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.