Scirpoides holoschoenus

Scirpoides holoschoenus (L.) Sojak (Cyperaceae)

Scirpus holoschoenus L., Holoschoenus vulgaris Link

Round-headed club-rush, Clwbfrwynen Bengrwn

Status in Britain: VULNERABLE.

Status in Europe: Not threatened.

In Britain, native populations of S. holoschoenus occur at Braunton Burrows, North Devon and Berrow Dunes, North Somerset, both in coastal dunes. Populations at Braunton Burrows occur in damp dune-slacks and in adjacent very low dunes. Frequent associates in the slacks include Agrostis stolonifera, Anagallis tenella, Juncus acutus, Mentha aquatica, Pulicaria dysenterica and Salix repens, whilst on the low dunes they include Carex arenaria, Festuca rubra, Hypochaeris radicata, Ligustrum vulgare, Ononis repens, Poa humilis and Rubus fruticosus. At Berrow, the single tiny patch occurs in a damp sandy hollow on a coastal golf course, together with Carex disticha, Festuca arundinacea, Hydrocotyle vulgaris, Juncus inflexus and Potentilla anserina.

S. holoschoenus is a densely tufted rhizomatous perennial which grows up to 150 cm tall but is usually about 100 cm. Flowering occurs in August and September, and only after a long hot summer do fruits containing viable seeds appear to form and ripen in quantity. After a favourable summer the seed bank may be substantial and short-term persistent, lasting for at least one year but fewer than five years (Thompson, et al. 1997). Seedling establishment typically occurs at sites with bare ground within reach of the water table but regeneration by seedlings has never occurred at Berrow (A.J.Willis, pers. comm.). The plant may form 'dunelets' by trapping and growing up through sand (Willis 1985), and this probably explains its occurrence in very low dunes at Braunton Burrows.

The stronghold for this species is at Braunton Burrows where the number of clumps has been estimated to exceed 3,000. S. holoschoenus also occurs sporadically as an introduction, particularly in the vicinity of docks and industrial areas. A single clump in Dorset, presumed to be an introduction, grows just above the high tide line in Poole Harbour, where associates include Elytrigia atherica, Picris echioides and Plantago lanceolata. Other presumed introductions have been reported from docks in Cardiff and Newport and from a brickyard in Kent. It is unclear whether any of these are extant; a colony at Newport was lost to development, though some plants may still survive on industrial land nearby.

The areas of Braunton Burrows where S. holoschoenus occurs currently receive no grazing other than by rabbits, and scrub encroachment is a continual threat. Rabbit viral haemorrhagic fever has recently been confirmed there, and this may pose a threat to the regeneration of S. holoschoenus should the level of rabbit-grazing decrease substantially. Scrub is kept in check by annual mowing in the months between November and March, and this management appears to be maintaining the population of S. holoschoenus. The recent de-declaration of Braunton Burrows as an NNR may put the species at further risk there. Plants occurring near industrial areas are liable to be lost when waste ground is developed or tidied, and such losses have increased in recent years. The species is tolerant of cold, but its range in Britain is probably limited by its requirement for high summer temperatures for regeneration by seed (Willis 1985). 

S. holoschoenus occurs widely in Europe, from Iberia northwards to Britain, and eastwards to central Russia and Greece. It also occurs in the Canary Islands, north-west Africa, and south-west and central Asia. It is often common in the southern parts of its range, including all the main Mediterranean islands, and occurs in a wide variety of open habitats.

J. H. S. Cox