Selecting Stones for a Rock Garden
In order to create a natural looking rock garden, you should try to use locally available stone wherever possible. This will ensure that it will harmonise with the local landscape and it will also cost a good deal less than rock that has been transported halfway across the country. If you do not live in a stone area, you may want to consider carefully whether a rockery would in fact be suitable for your garden.
Sandstone, with its clearly visible layers or strata, is one of the most appropriate rocks for rockeries, especially if you can buy it pre-weathered. One great benefit of using rocks with stratum lines is that they may easily be split.
Tufa is a porous rock that is formed as calcium carbonate deposits around mineral springs. It is an excellent choice for the rock garden as its many air pockets make it light enough to be easily handled and transported. Its soft, porous nature also means that plants may be grown in cavities on its surface as well as in crevices between the stones.
Limestone can also be a good choice. However, never use limestone taken from the natural rock formations known as limestone pavements; so much of this stone has been taken for use in gardens that it has become an endangered ecosystem. However, limestone can be obtained from legitimate quarrying in the Pennines, Oxfordshire, the Cotswolds and Mendip Hills.
Limestone pavement rock may be offered for sale under a variety of names, such as Cumberland stone, water-worn limestone, Westmorland stone, Irish water stone and Irish limestone. Gardeners should avoid these types of stone in favour of rocks from less environmentally sensitive sources.
Hard, igneous rock (such as granite and basalt) tends to be relatively inexpensive; however, its lack of strata makes it difficult to work with. It can also take years to acquire a weathered appearance, which can make it look rather unnatural. You should also avoid using soft, quick-weathering rock such as shale and chalk.
If possible, select the individual pieces yourself, either at a local quarry or garden centre. You will be able to create a more natural-looking outcrop if you use a range of stones in different sizes. Bear in mind though, that the rocks will be positioned in the garden so that at least a third of their bulk is buried below ground.
Rock is usually sold by the ton, and you will get less or more for your money depending on how heavy it is; granite is a heavy rock, whereas sandstone is far lighter. Any well-proportioned rock garden or outcrop will probably use at least ten tons.
You may also want to consider using artificial rocks; these are available from garden centres and are lighter to install and kinder to the environment.