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
With Britain’s most extensive areas of beech woodland and some of our richest chalk grasslands, it’s no wonder the Chilterns are home to an exceptional diversity of flowers, including rare orchids and unique plants found nowhere else.
This Important Plant Area is home to:
• Some of the UK’s most important populations of eyebrights
• An exceptional diversity of vascular plants growing in dry chalk grassland and deciduous woodland
The gentle, rounded hills of the Chilterns lie on an outcrop of chalk rock that stretches all the way from Dorset to Yorkshire. In the Chilterns the chalk is tilted and its north-western edge forms a distinct ridge, with a characteristic steep ‘escarpment’ slope overlooking the Vale of Aylesbury. This slope is deeply indented by dry river valleys known as ‘combes’. In the other direction, the chalk slope ‘dips’ gently down towards the London Basin.
The landscape here is heavily wooded, especially with beech, and gives way in the north to the open chalk downland of Ivinghoe Beacon and Dunstable Downs.
This is one of the most heavily wooded parts of England, with 21% of the land covered in forest. Much of this is ancient semi-natural woodland of beech, ash and yew. Under the heavy canopy, little light reaches the ground so the flora is often poorly developed. But even in such spots orchids can often be found, including white helleborine, broad-leaved helleborine and bird's-nest orchid. Where more light comes through, a lush carpet of dog's mercury, enchanter's nightshade, wood sorrel, bluebells, wood anemone and woodruff occur in the dappled shade. These woods are also a major stronghold of the very rare coralroot, a relative of cuckooflower with large pale lavender flowers, and include site for the stunning red helleborine orchid, known only from here and two other places in Britain.
On the steep escarpment slopes, substantial areas of flower-rich calcareous grassland and scrub can be found with dogwood, hawthorn, wayfaring-tree, whitebeam and, occasionally, juniper. Some areas are dominated by box, a small evergreen tree that may be native to this area.
The closely-grazed chalk downland can be famously flower-rich and there are too many to mention, with up to 50 species per square metre. The most heavily grazed areas are 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 other flowers can flourish including rockrose, purging flax, felwort, salad burnet, dropwort, ploughman's spikenard, clustered bellflower and wild thyme. Less common plants like bastard toadflax and chalk milkwort also grow here, along with at least four species of Eyebright, including rare chalk eyebright. In a few places, the stunningly beautiful Pasque flower can be seen in bloom around Easter. Rarest of all, though, is Chiltern gentian, found only here and nowhere else in Britain.
The chalk downlands are home to a number of orchids, with common spotted orchid, chalk fragrant orchid, pyramidal orchid and bee orchid all easily seen. Much rarer though are the elegant lady orchid, with a flower that really does look like a lady in a bonnet and skirt, and monkey orchid, with flowers that really do look like a little monkey!