Scientific name Briza media – Thymus polytrichus grassland
Common name Quaking-grass – Wild Thyme grassland
Community code GL3A


GL3A: Briza media – Thymus polytrichus grassland  GL3A: Briza media – Thymus polytrichus grassland  GL3A map: Briza media – Thymus polytrichus grassland

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This is typically a very species-rich assemblage and has a large number of constants. The main graminoids are Carex flacca, Briza media, Anthoxanthum odoratum and Sesleria caerulea with Carex caryophyllea, Festuca spp. and Koeleria macrantha being less frequent but still characteristic plants. The turf is typically rather low. The plentiful and colourful forb component contains several good calcareous indicators such as Thymus polytrichus, Linum catharticum, Galium verum, Lotus corniculatus, Campanula rotundifolia, Polygala vulgaris, Leucanthemum vulgare and Pilosella officinarum. Other forbs present usually include Succisa pratensis, Plantago lanceolata, Potentilla erecta, Centaurea nigra, Viola riviniana and Euphrasia officinalis agg. The calcicole moss Ctenidium molluscum is frequent.



This community comprises swards of calcareous grassland on shallow, well-drained soils of poor fertility. It is the typical grassland community to be found in association with limestone pavement and eskers and occurs at middling altitudes, often on sloping ground which improves the drainage. Consequently, it has a distinct geographical distribution, with some of the best examples being concentrated in the Burren and in the Dartry Mountains.



There are two sub-communities described. The Sesleria caerulea – Tortella tortuosa sub-community (GL3Ai) is found in association with limestone pavement and species indicative of that habitat have higher frequency than in the more typical Cynosurus cristatus – Centaurea nigra sub-community (GL3Aii). These indicative species include Geranium sanguineum, Asperula cynanchica, Neckera crispa, Carlina vulgaris and Tortella tortuosa. Sesleria caerulea is almost always present in sub-community GL3Ai, but may also occur in GL3Aii


Similar communities

This is generally a distinct community which differs from others in the GL3 group in the richness of species and presence of numerous calcicole species.


Conservation value

This is a very species-rich grassland community of which most examples correspond with the priority EU HD Annex I habitat 6210 Orchid-rich calcareous grassland*. In addition to supporting populations of rare orchids (e.g. Gymnadenia conopsea, Ophrys apifera) and being important for a range of pollinators, permanent pastures of this type can be notable for their anthills. Rare swards of the Dartry Mountains with Silene acaulis match the EU HD Annex I habitat 6170 Alpine and subalpine calcareous grassland.



These swards are managed as light intensity grazing land for cattle or horses. The main threats to these grasslands include improvement and abandonment. As they tend to occur on limestone or eskers these sites are also at risk from quarrying.