Flowers of the Limestone Pavement

by Tony Bond FRPS

One of the most distinctive habitats in Britain is limestone pavement. Examples are to be found in the Carboniferous limestone which stretches from Morecombe Bay eastwards through southern Cumbria and North Yorkshire. Limestone pavement is not restricted to Britain - the Burren, in the Republic of Ireland is famous for this habitat.

The origins of limestone pavement go back to the last Ice Age when glaciers covered northern England. These acted as giant planing machines in the places where we now find pavements. When the glaciers retreated they left these flat areas of limestone and dumped the occasional erratic. Since the retreat of the glaciers, rainwater has carved the pavements in blocks of limestone, clints, divided by deep fissures known as grikes. Unfortunately, the fascinating shapes and contours created by water made the rock very attractive to gardeners. During the 1970s it was realised that unless positive action was taken, an irreplaceable habitat would be lost. This led to the purchase of Gait Barrows National Nature Reserve (NNR), Silverdale, in 1977 by what was then the Nature Conservancy Council. Gait Barrows is the most accessible limestone pavement reserve and contains both damaged and undamaged pavement. Since the seventies, gardeners have been discouraged from using limestone by campaigns to stop extraction - you may remember one such campaign run by the late, great Geoff Hamilton of BBC Gardeners World. However, I have no doubt that extraction, legal or otherwise, is still going on somewhere.

Globe Flower (Trollius europaeus)

Part of the fascination of limestone pavement is that you can find yourself looking at widely differing habitats all at the same time! There are enormous differences between the cool, dark grikes and exposed limestone and these result in very different types of flora. With the passage of time, soils have built up on the surface which may be of sufficient depth to support trees - Ash (Fraxinus excelsior) and Hazel (Corylus avellana) are the most common.

Dark Red Helleborine (Epipactis atrorubens)

Conditions in the grikes are ideal for a range of plants which we would normally associate with a woodland habitat. Ferns are prolific, the commonest being Hartstonge (Phyllitis scolopendrium). Others include Hard Shield Fern (Polystichum aculeatum) and the nationally rare Rigid Buckler Fern (Dryopteris villarsii). Flowering plants are found in the shallower grikes and these can vary from the very common Ramsons (Allium ursinum) to the rare Angular Solomon’s Seal (Polygonatum odoratum) and Dark Red Helleborine (Epipactis atrorubens).

Birdseye Primrose (Primula farinosa)

On the surface, where there are accumulations of soil, you will find a wide range of limestone loving plants. In the spring these include such favourites as Early Purple Orchid (Orchis mascula), followed by Thyme (Thymus drucei), Common Rock-rose (Helianthemum chamaecistus) and Birdsfoot Trefoil (Lotus corniculatus). While limestone tends to be very dry, any wet flushes may contain two specialities, Globe Flower (Trollius europaeus) and Birdseye Primrose (Primula farinosa).

Ramsons (Allium ursinum)

If you are not already familiar with the delights of limestone pavement and wish to see them for yourself, you do need to be aware of the dangers:

• The rock is very slippery when wet
• Vegetation can often conceal grikes.

A permit is required to visit Gait Barrows and may be obtained by writing to:
Robert Petley-Jones - Site Manager
South Cumbria and North Lancashire NNRs
English Nature
Fish House Lane, Haverthwaite, Ulverston, Cumbria, LA12 8PE

Members of the RSPB may wish to combine a visit to Gait Barrows with Leighton Moss, which is just down the road.