Cynodon dactylon

Cynodon dactylon (L.) Pers. (Poaceae)

Bermuda grass, Gwair Bermuda

Status in Britain: VULNERABLE.

Status in Europe: Not threatened.

This species is principally a plant of sandy ground in coastal areas of southern England and Wales. Most records are from the lawns of ornamental gardens or along the sea-front of south coast resorts, where they are managed for their amenity value and are mown regularly. In such places, C. dactylon may be mono-dominant, or grow in a mixed sward with other robust species including Bellis perennis, Carex arenaria, Elytrigia repens, Plantago coronopus and Poa annua. However, it also occurs in semi-natural habitat in extreme south-west England. John Ray (1724) noted that it was "found by Mr Newton on the sandy shores between Pensans and Marketjeu in Cornwall plentifully". It still occurs along the shore between Penzance and Marazion, together with typical dune species including Beta vulgaris, Festuca rubra, Honkenya peploides, Hypochaeris radicata, Plantago coronopus and Trifolium occidentale. Other colonies are found on nearby roadsides with maritime ruderal species. 

C. dactylon is a tough perennial grass spreading by extensive, creeping rhizomes. Flowering is in August and September, though it may not flower where severely trampled. It is not known whether there is effective recruitment by seed, but vegetative spread is likely to be the more important.

It seems certain that this species is an introduction at most of its British sites, though positive evidence of planting is hard to come by. However, the long established colonies near Penzance (and in Jersey) have a stronger claim to native status, and are mapped as such. Ryves, et al. (1996) consider this species might be native in Britain, though Margetts & David (1981) more cautiously record it as "probably originally introduced". As a possible native species or ancient denizen, its conservation should not be disregarded, especially in its fore-dune sites. It also occurs more widely as a casual from wool shoddy and other sources.

This grass can withstand a good deal of trampling, and can survive on dry and impoverished ground, often remaining green when other grasses are parched brown. The main threat to the species may be from coastal development or local maintenance works. For instance, part of Newton's original population was destroyed in 1994 by the construction of a sewage outfall, and a long established site in Poole by roadworks.

C. dactylon is one of the most widespread grasses in warm temperate and tropical regions. In Europe it is found throughout the west and south, and eastwards to Ukraine.

R. M. Walls