A tufted perennial herb of acidic rock ledges, screes and stony mountain plateaux. From 760 m to 1100 m (Ben Nevis, Westerness).
P. flexuosa is now known from more 10-km squares than were mapped in the 1962 Atlas. Since 1970 it has been recorded from about a dozen sites, most of these supporting only very small populations. P. x jemtlandica (P. flexuosa x P. alpina) occurs with P. flexuosa at some sites, and may perhaps have given rise to some mis-identifications.
European Arctic-montane element; also in N. America.
Count of 10km squares in Great Britain: 8
Count of 10km squares in Ireland: 0
Count of 10km squares in the Channel Isles: 0
RDB Species Accounts
Poa flexuosa Sm. (Poaceae)
Wavy meadow-grass, Tràthach Casta
Status in Britain: VULNERABLE.
Status in Europe: Not threatened. Endemic.
P. flexuosa is a montane grass occurring on acidic rocks from 760 to 1,100 metres. Clumps grow between stones on plateaux, on open scree and on stone ledges, mostly in isolation without immediate associates. However, plants growing in the vicinity may include Alchemilla alpina and Festuca vivipara, and less commonly Huperzia selago, Juncus trifidus, Luzula spicata, Saxifraga stellaris and Silene acaulis.
It is a tufted perennial, lacking rhizomes, flowering in July and August. Little seems to be known of the longevity of plants or of its reproductive biology, including the factors controlling seed-set and recruitment.
During the past twenty years, P. flexuosa has been recorded in about twelve sites in eight hectads, in Aberdeenshire, Moray, Ross-shire and Inverness, and may still be extant in all sites for which there is only a pre-1987 record. Records from Perthshire are now considered to be doubtful (H.A.McAllistair, pers. comm.). Much the largest known population, of 200-300 plants, occurs on scree slopes on Ben Nevis. Elsewhere, populations are small: for example, colonies of 36 and eight plants on Liathach in 1995, seventeen on Beinn Alligin the same year, and two in Coire an Lochan, Cairngorm in 1991. The rare hybrid P. x jemtlandica (P. flexuosa x P. alpina) grows at some of the P. flexuosa sites.
Small populations are threatened by human activities, including climbing, in the more popular localities, whilst in Ross-shire, damage has been caused by deer trampling the tussocks (Perring & Farrell 1983).
P. flexuosa is endemic to montane regions of northern and western Europe, occurring only in Iceland, Scotland, Norway and Sweden. Plants from Greenland and the Alps, hitherto considered to be forms of P. flexuosa, are now treated as distinct species.
P. J. O. Trist
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.