The Chilterns IPA
Location: North west of London, extending from the Thames in the south west to just beyond Luton in the north east.
Grid Reference: SP 762 040
The Chilterns IPA has been recognised as one of 165 Important Plant Areas in the UK.
The key features of this IPA are:
The Chilterns are a beautiful, unspoilt corner of England, beginning in Oxfordshire in the Thames Valley and stretching north-east through Buckinghamshire and Bedfordshire to Hitchin in Hertfordshire. In 1965, 833 square kilometres of the Chilterns were designated by the government as an Area of Outstanding Natural Beauty (AONB).
The Chilterns' rounded hills are part of the chalk ridge which crosses England from Dorset to Yorkshire. The characteristic scarp slope, indented by combes and cut by a number of gaps, looks out north over the panorama of the Vale of Aylesbury. The dip slope, dissected by steep dry valleys, curves gently down into the London Basin. The heavily wooded character of the Chilterns, gives way in the north to the open downland of Ivinghoe Beacon and Dunstable Downs. The Chilterns contain an important diversity of habitats ranging from chalk grassland to the country's most extensive areas of beech woodland, with the finest stretches protected as National Nature Reserves.
Woodland is a dominant feature of the IPA with a characteristic ancient semi-natural woodland of beech, ash and yew. The heavily-shaded field layer is poorly developed beneath the trees, but becomes lusher under more open canopy where carpets of dog's mercury, enchanter's nightshade and woodruff occur. The steeper slopes and valley sides still support substantial areas of unimproved calcareous grassland and scrub, where some juniper can be found. In addition there are some areas dominated by the dwarf evergreen tree, box , a rare woodland type nationally which may be native to this area.
Where the downland consists mainly of close-grazed, species-rich turf, it is dominated by grasses, whereas the more neutral grassland support grasses together with an unusual abundance of herbs such as horseshoe vetch, rockrose and dwarf thistle as well as a notable abundance of uncommon plants like bastard toadflax and chalk milkwort.
The most heavily grazed areas have a sparse flora dominated by short herbs such as biting stonecrop, eyebright, wild strawberry and the nationally uncommon candytuft , a species which has its British distribution centred on the western scarp of the Chilterns. Where grazing is less intense there is a dense, species-rich sward dominated by sheep's fescue and supporting a wide range of broadleaved herbs including rockrose, purging flax, felwort, salad burnet, dropwort, ploughman's spikenard, clustered bellflower, wild thyme, and the nationally scarce Pasque flower and Chiltern gentian.
The chalk downlands are home to a number of orchids including the common spotted, pyramidal, bee, lady and the nationally rare monkey orchid, a Red Data Book species. Sunken lanes are a characteristic feature and the hedgebanks often support species such as spindle, dogwood, wild privet, hazel and field maple.