Purple moor grass

Molinia caerulea is a perennial herbaceous bunchgrass (tussock-forming), growing up to 120 cm (47 in) tall (taller when sheltered by gorse and heather), with many closely packed stems. The leaves are coarse, green, taper to a point, long, flat and sometimes slightly hairy on top. Due to the dense tussock it is very resistant to heath fires. Its ligule is a ring of hairs, as in heath grass (Danthonia decumbens). The long narrow purple spikelets are a major identification feature – the panicle is 15 cm (6 in) long. It flowers between July and September, later than any other species.

The caterpillars of some Lepidoptera use it as a foodplant, e.g., the chequered skipper (Carterocephalus palaemon). Claviceps purpurea is an ascomycetous fungus which grows on the seeds of purple moor grass. Purple moor grass and rush pastures were a United Kingdom Biodiversity Action Plan habitat, on account of their rarity. However, in 2025 it was reported that purple moor grass was spreading over Britain and displacing other vegetation in a way characteristic of invasive species, although it is native. Over the previous fifty years it had spread over large upland areas in much of Wales, Dartmoor, Exmoor, the Pennines, the Peak District, North York Moors, Yorkshire Dales and many parts of Scotland. Areas of moor grass support very little bird or insect life – a characteristic described as a "terrestrial dead zone" or desert – and is difficult for humans to walk through. It is not controlled by herbivores, who will favour other plant species over the grass and will not eat it whatsoever past early summer, when its nutritional value falls heavily. …

Molinia caerulea is cultivated for its panicles of purple spikelets on yellow stems. In cultivation it grows to 1.5 m (5 ft) tall by 40 cm (16 in) broad. Numerous cultivars have been selected, of which the following have gained the Royal Horticultural Society's Award of Garden Merit:

M. caerulea subsp. arundinacea 'Windspiel' M. caerulea subsp. caerulea 'Edith Dudszus' M. caerulea subsp. caerulea 'Moorhexe' M. caerulea subsp. caerulea 'Poul Petersen' M. caerulea subsp. caerulea 'Variegata'