Why Would You Want A Rock Garden?
Your rock garden or rockery will be an attractive focal point whose natural characteristics will attractively evolve over the seasons and years. They are low maintenance and, constructed in a naturalistic fashion, home to a huge and fascinating variety of plants that provide long lasting interest and attractive colour throughout the year.
The Site
Siting the rockery needs careful consideration, you'll need an open aspect away from trees and shade. Most alpine plants appreciate copious amounts sunlight and dislike being waterlogged - which is why they are at their most vulnerable over winter especially if the rock garden has been sited incorrectly in a shady damp location with soil that hasn't been prepared properly.
Rock Type
Geology varies throughout the country so initially you should decide whether to go for stones that reflect your part of the world or choose completely different rock that might have characteristics that are more appealing or are more in keeping with the garden's design.
Sedimentary rock such as limestone from the West Country or sandstone from the Midlands will weather, developing a lovely patina, and slowly alter in shape while non-sedimentary rock such as granite is harder and has perhaps a more dramatic presence. Whatever stone you choose, study natural formations and build the rockery using different shapes and various sized pieces of the preferred type to create a natural landscape.
Construction
Late winter / early spring is the ideal time to start work when the ground is easier to work and the plants have a full season to establish themselves. Mark out roughly where the rockery is to go and clear away any grass and weeds. Break up the ground and put down a layer of hardcore or rubble, this will ensure effective drainage and a stable base. On top lay a covering of weed suppressant fabric.
If you want a rockery of any height, build a mound with soil, stones, bricks, gravel and other similar material. Cover the ground with with a mix of compost, grit and leaf mould or coir and then it's probably a good idea to allow that to settle for a few days before starting to add rocks.
When siting the rocks, start with the largest ones at the base locate them fairly close together, bedding them solidly into the soil while leaving gaps and larger spaces above, below and to the side for planting. Ensure they are firmly in place and fill gaps with the compost mix You can now leave the rockery for a week. Soak it with a hose if there is no rainfall to help every element settle into place.
Planting
There's no shortage of alpine plants to provide all year colour and interest. Kabschia saxifrages will flower from February to April, and Cyclamen coum and Anemone hepatica or pennywort are also useful for these months. From May, gentians and phloxes can take over followed by rock roses and geraniums, bell flowers and many others. Cyananthus will flower into October and Saxifraga fortunei last into November.
To provide evergreen interest and structure over winter and throughout the year why not plant some dwarf conifers. Plant into the compost mix and cover with a scree of small stones, grit and gravel, this will act as a weed suppressing mulch and also help to approximate the appearance of a rocky outcrop. Maintenance is very low, any fallen leaves will need to be removed in the autumn but no fertilizer is normally required and water is necessary only in very dry conditions.