Summary1. This account presents information on all aspects of the biology of Cirsium arvense that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of the British Isles: distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, history, conservation and management. 2. Cirsium arvense, creeping thistle (Californian thistle, Canada thistle), one of the world's most troublesome and persistent weeds, is native to Europe and the east northern hemisphere but introduced to North America and the southern hemisphere. Latitudinal distribution north or south is limited by low winter and summer maximum temperatures and by a long day requirement for flowering. 3. Cirsium arvense is believed to have originated in the temperate Middle East and its spread has closely followed human migration and agricultural activity. Colonization of new sites is by seed which establishes best in bare or disturbed ground, mirroring its prehistoric ecology as an opportunist pioneer of bare ground and organic residues. It is now a widespread and scheduled agricultural weed in both arable crops and pastures and also a constituent in over 70 British (National Vegetation Classification) plant communities, occurring mainly on waste neglected land, roadsides, hedgerows and disturbed areas. 4. Its presence in crops leads to yield losses and in pastures seriously interferes with utilization due to the deterrent effect of the leaf spines on grazing animals. This has led to a long history of investigation into control measures: mechanical, chemical, biological and integrated, which are summarized. Combination treatments and integrated control have achieved some success but effective control requires follow-up procedures over a number of seasons. Climate change studies suggest C. arvense could grow better and be more difficult to control in future. 5. Success and persistence derives from an extensive, far-creeping and deep rooting system which ensures survival and rapid vegetative spread under a wide range of soil and management conditions, and a means of escape from sub-aerial control treatments. New adventitious buds capable of shoot development can arise at any point along the horizontal roots, even when these are cut into pieces or damaged. Root buds remain dormant until released from dormancy through damage or decay of the aerial shoots. Carbohydrate root reserves, stored in swollen cortical tissue, fall to a minimum just before flowering and are then replenished for perennation during the subsequent winter. Strategies for control aim to treat the plant when root carbohydrate reserves are at a minimum, to exhaust these reserves and to prevent replenishment for further perennation. 6. Balanced against its difficulty as a weed, C. arvense has significant conservation value as a host to numerous insects, many attracted by copi...

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Three smaJI plot exp>eriments were conducted to investigate the effects of species of grass and forbs, defoliation regime, inclusion of white clover and forb blend on the herbage dry matter (DM) yield, botanical composition and mineral content of swards managed with zero fertilizer inputs. The results of all three experiments were characterized by decline in herbage production and large variations in treatment effects over the harvest period.When sown singly with a standard grass mix the species that competed well with grasses and produced annual forb herbage yields greater than 20 t DM ha"' were black knapweed, oxeye daisy, ribwort plantain, bumet. birdsfoot trefoil, chicory, kidney vetch, red clover and white clover. When sown singly with a standard forb mix, grass species significantly affected the annual yield of total (/'<005). grass (F

Grain maize in south-east England showed a markedly flat-topped curvilinear response between density and grain yield, maximum yields being obtained over a range of 80,000-120,000 plants/ha, but yields were reduced at less than 70,000 plants/ha. A general density recommendation of 80,000 -90,000 plants/ha is suggested, or a seed rate of 95,000 seeds/ha to allow for germination losses. Yields of cv Anjou 210 and DeKalb 202 showed some decline when the density exceeded 100,000 plants/ha, whereas yields of Pioneer 131 increased above this value and 100,000 plants/ha can hence be recommended. Although planting above the optimum density markedly increased the incidence of stem lodging at harvest, only a minor delay in stage of maturity occurred.Following its rapid spread into northern Europe, grain maize was introduced into south and east England during the early 1970s as a potential cereal break crop. Spacing recommendations at that time were based on European practices, which ranged from 80,000 plants/ha for established plant stands in the Netherlands to 90,000 plants/ha in northern France (Anon., 1973), and an intermediate figure of 85,000-90,000 plants/ha was initially suggested in Britain (Milbourn, 1975). Studies on hand-harvested plots over several seasons in central England (Bunting, 1973) also suggested that optimum densities for grain maize in Britain lay between 70,000 and 100,000 plants/ha, depending on variety.In view of the differences in latitude and climatic conditions between the potential grain maize areas of Britain and those of northern Europe, and also because newer, earlier-maturing hybrids were being introduced into Britain, confirmation of the optimum planting density under normal farm conditions was required. A series of density x variety experiments, drilled and harvested mechanically, were therefore laid down at Wye College, Kent, and at six other sites in potential grain maize areas in south and east England during the seasons 1971-74. EXPERIMENTAL METHODSThe range in seed rates tested was 54,000-163,000 seeds/ha, to give established plant densities distributed widely about a mean of 100,000 plants/ha. Varieties from the early group (0-1 rating in the French maize variety classification, 0-200 in the FAO classification) that were being widely used by growers of grain maize were chosen as follows: