Carex humilis (Dwarf Sedge)
A perennial herb of closely-grazed, calcareous grassland, especially on steep slopes on chalk downland. Over limestone it also occurs locally in grazed pastures as well as on field margins, track-sides and rock outcrops. It fruits freely, but regeneration from seed and spread into new areas has only rarely been reported. Lowland.
The overall distribution of C. humilis is stable, but detailed studies in Dorset have revealed that over 10% of its recorded sites have been ploughed up (Pearman, 1997). Many extant sites now have some form of statutory protection, but the smaller ones are often ungrazed.
Eurasian Temperate element, with a continental distribution in W. Europe.
Light (Ellenberg): 8
Moisture (Ellenberg): 3
Reaction (Ellenberg): 8
Nitrogen (Ellenberg): 2
Salt Tolerance (Ellenberg): 0
January Mean Temperature (Celsius): 3.9
July Mean Temperature (Celsius): 16.1
Annual Precipitation (mm): 845
Count of 10km squares in Great Britain: 30
Count of 10km squares in Ireland: 0
Count of 10km squares in the Channel Isles: 0
Atlas Change Index: -0.01
Scarce Atlas Account
Carex humilis Leysser
This species is locally abundant in closed turf on close-grazed chalk downland, with a few outliers in more open conditions on Carboniferous limestone rocks to the west, It is now almost restricted to steeper slopes and earthworks, out of reach of ploughing, It favours southerly and south-westerly aspects as it is able to withstand drought, and in such situations competition from other species is presumably much reduced. Associated species on chalk downland occasionally include the nationally scarce species Tephroseris integrifolia and Thesium humifusum. On the Carboniferous limestone it occurs in a community with a large number of nationally rare and scarce species, including Helianthemum apenninum, Koeleria vallesiana, Trinia glauca and the moss Scorpiurium circinnatum. Experimental studies in the Avon Gorge indicate that C. humilis benefits from the addition of mineral nutrient mixtures which are deficient in phosphorus (Willis 1989). It is confined to the lowlands.
C. humilis is a long-lived perennial, gradually spreading vegetatively to form mats 15cm or more across. Recent observations have shown that ripe seed is spread by ants and seedlings are occasionally found on bare ground in the Avon Gorge (Lovatt 1982) and at Brean Down. It is also able to spread by the re-rooting of detached pieces (David 1979a; Lovatt 1982), especially on steeper slopes, and possibly where it is ploughed, and its presence on ancient earthworks may result from this, unless they were thatched with turves. Although the species rarely behaves as a colonist, at Blandford Camp it has succeeded in establishing itself on a variety of manmade habitats, including recreation fields and the central reservations of roads.
Although the map shows little contraction of range, very many individual sites have been lost. In Dorset 17 out of a total of 49 sites were lost between 1860 and 1990, and many others in Dorset and Wiltshire much reduced in size. This reduction is continuing where sites are not being grazed or where cattle, with their extra weight, rather than sheep, are used. Aerial fertilising has also reduced some populations, especially in Wiltshire. In the Wye Valley trampling has completely destroyed some sites. It has been much reduced but not completely eliminated by public pressure at Stonehenge.
It is widespread in Europe, except Scandinavia, and extends east to Manchuria.
For a detailed account of the British distribution, see David (1979a, 1982a).
D. A. Pearman
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
Sedges of the British Isles. Botanical Society of the British Isles Handbook no. 1, edn 2,
, London, (1982)
Vergleichende Chorologie der zentraleuropäischen Flora. Volume 1. 2 vols,
, Jena, (1965)
Scarce plants in Britain,
, Peterborough, (1994)