Polygala calcarea

Tracheophyta MagnoliopsidaPolygalaceaePolygalaPolygala calcarea

Ecology

A perennial herb found in tightly-grazed chalk and limestone grassland, usually on warm S.-facing slopes. It is a poor competitor which disappears if insufficient grazing allows coarser grasses to become dominant. Lowland.

Status

Native

World Distribution

Oceanic Southern-temperate element.

Broad Habitats

Calcareous grassland (includes lowland and montane types)

Light (Ellenberg): 7

Moisture (Ellenberg): 3

Reaction (Ellenberg): 8

Nitrogen (Ellenberg): 2

0

Salt Tolerance (Ellenberg): 0

January Mean Temperature (Celsius): 3.7

July Mean Temperature (Celsius): 16.2

Annual Precipitation (mm): 783

Life form information

Height (cm): 10

Perennation - primary

Perennial

Life Form - primary

Chamaephyte

Woodiness

Herbaceous

Clonality - primary

Little or no vegetative spread

Count of 10km squares in Great Britain: 153

Count of 10km squares in Ireland: 0

Count of 10km squares in the Channel Isles: 0

Atlas Change Index: -0.37

Distribution information

JNCC Designations

NHMSYS0000461830

Scarce Atlas Account

Scarce Atlas Account: 

Polygala calcarea F. Schultz 

Chalk milkwort

Status: not scarce

 

This procumbent perennial is woody at the base with basal leaf-rosettes that persist throughout the winter. It grows in very short, ancient Festuca ovina grassland on chalk and Jurassic oolite, on very shallow soils, usually on warm, south-facing sites, often associated with Hippocrepis comosa, and sometimes with Ophrys sphegodes, Tephroseris integrifolia and Thesium humifusum. It is confined to the lowlands.

P. calcarea is a perennial and reproduces by both stolons and seed. It can colonise new sites adjacent to existing ones (e.g. chalk banks created by new or widened roads in downland areas) but not very rapidly.

This species is fairly stable in the core of its distribution but has retreated in places near the edge of its range in Somerset and in the outlying area in Leicestershire and Lincolnshire. It is very dependent on the maintenance of short, unfertilised turf such as that produced by sheep grazing, and it disappears if this is replaced by coarse grasses or scrub.

P. calcarea is a plant of calcareous grasslands in western Europe only, not extending north of Belgium or very far east of the Rhine. 

P. calcarea has often been wrongly reported owing to confusion with P. vulgaris, particularly in certain areas of East Kent and West Sussex where there is no good evidence that it occurs, but the better description of it in modern Floras should avoid this in future. The blunt, obovate basal and stem leaves are diagnostic here, but flower colour varies enormously, as in P. vulgaris. The isolated populations in East Kent and on the Leicestershire-Lincolnshire oolite have smaller leaves and flowers than the main population from mid-Kent to Dorset, Somerset and the Cotswolds. More biometrical studies are required but the outliers appear to have been isolated for a long period.

 

F. Rose

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.

Atlas text references

Atlas (56b)
Meusel H, Jäger E, Rauschert S, Weinert E
1978.  Vergleichende Chorologie der zentraleuropäischen Flora. Volume 2. 2 vols.
Stewart A, Pearman DA, Preston CD
1994.  Scarce plants in Britain.