Ammophila coast coastal coastline colonist Cornish cornwall dune England english grass Great Britain habitat marram natural nature plant sand shore stabilise Caryophyllaceae Devon flowers little petals small spring stamens Stellaria stichwort stigma tiny verge white wild berries bush crataegus field fruits haws hawthorn hill landscape meadow red shrub South Downs summer Sussex access barrier clouds countryside entrance exercise footpath gate sky walk wooden abundance abundant Apiaceae Bedfordshire damp many profusion riverside umbellifer branch current danger flow green powerful river strong surge surging thames tree violent water arch chalk cliff face hole kent low peephole rock sea stone tide crop farm peace plain rural view woodland flora gorse spiny Ulex yellow