An annual of well-drained grasslands on calcareous substrates, especially on S.-facing slopes where the turf is broken by patches of crumbling soil. It used to be a frequent weed of cornfields, and is an occasional wool and grain casual. Lowland.
G. ventricosum was first recorded in 1690 and is possibly native in grassland in S.W. Britain and in the Channel Islands, where it has been found to be much more widespread than shown in the 1962 Atlas. Formerly it was regarded as an arable weed, but it had largely vanished from such habitats by 1930. As habitat details are not available for many old records, they are mapped as if they are native.
Count of 10km squares in Great Britain: 159
Count of 10km squares in Ireland: 0
Count of 10km squares in the Channel Isles: 2
Atlas Change Index: -0.48
RDB Species Accounts
Gastridium ventricosum (Gouan) Schinz & Thell. (Poaceae)
Status in Britain: LOWER RISK - Nationally Scarce.
Status in Europe: Not threatened.
G. ventricosum is a native of well-drained, open grassland on calcareous soils. These soils are invariably shallow, and frequently overlie rock, their texture varying only slightly from a silty clay loam to a sandy loam (Trist 1986). Most sites are on slopes, which are often steep, and are usually south-facing, exposed to wind erosion and in close proximity to the sea or maritime influence. Some of the Somerset sites are now some distance inland (up to 26 km) but are on slopes that were once coastline when the Somerset Levels were covered by the sea. Plant associates in these habitats are Koeleria macrantha, Pilosella officinarum, Sanguisorba minor, Thymus polytrichus, and many other plants of well-drained calcareous soils, including local species such as Althaea hirsuta in Somerset, Gentianella anglica and Ophrys sphegodes in Dorset, Anisantha madritensis and Potentilla neumanniana in the Avon Gorge and Scilla verna in the Gower. Bare ground is always present (Lovatt 1981). G. ventricosum was formerly frequently recorded as an arable colonist, with associates such as Agrostis gigantea, Polygonum aviculare and Veronica persica (Trist 1983).
G. ventricosum is an annual, germinating in autumn, and is frost-sensitive (Trist 1986). Numbers of flowering spikes vary greatly, depending on climatic conditions and competition from other species. Lovatt (1981) suggests that two more or less consecutive hot dry summers are required for reappearance of G. ventricosum in quantity, and that the optimum conditions for seed production are a mild winter, a damp warm spring and a hot June. The longevity of the seed-bank is not known.
There seems to be little evidence of any decline in the native distribution of G. ventricosum in its semi-natural habitats. Indeed recent recording work, particularly in Somerset, but also in Dorset and Glamorgan, has shown that the plant is much more widespread than was previously suspected. It is assumed that greater recording effort is the reason, although recent summer droughts opening up the vegetation may have contributed. Certainly G. ventricosum flourishes only in open situations, and grazing, especially by rabbits, is essential to its survival. It can survive for short periods amongst taller vegetation, by increasing its height as a response to deprivation of light (Trist 1986), but this is only a temporary measure; open ground is necessary for reproduction.
G. ventricosum has almost vanished from arable habitats (the source of most of its records in south-east England) because of the usual combination of cleaner seed and herbicides. But it still persists in one such locality in South Hampshire, and appeared recently in enormous quantity in set-aside arable fields in Dorset, though it may have spread to these fields from a native grassland site (Preston & Pearman 1991). It has also frequently been recorded as a casual. But these arable and casual records have influenced perceptions of decline in this species. Now that its native habitat is better understood and better explored the true position of its status can be appreciated.
G. ventricosum is widespread over west and central Europe, around the Mediterranean, and eastwards to Iraq, and it is found on grassy hillsides and as an arable weed throughout this range.
I. P. Green and D. A. Pearman
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.
Atlas text references
Alien grasses of the British Isles,
, London, (1996)
The distribution, ecology, history and status of Gastridium ventricosum (Gouan) Schinz & Thell. in the British Isles,
, Watsonia, Volume 16, p.43-54, (1986)
British Red Data Books. 1. Vascular plants, edn 3,
, Peterborough, (1999)