How to build a rock garden

Before attempting to build a rock garden, the gardener should have in mind (if not on paper) a plan of the basic design he or she wishes to make. To get an idea of the possibilities, visit a rock garden in one of the many botanical gardens throughout the country. Here's a step-by-step guide on building a rock garden that suits your landscape.

• If you don't have rocks on your property, purchase them from a garden centre or landscape contractor.
• Whenever possible, choose the pieces yourself, selecting for uniformity of colour and texture. If you order from a supplier, ask for a variety of sizes.
• Large rocks, although not always easy to move and put in place, are likely to provide the most natural effects, but smaller sizes will be needed, too.
• You will also need a supply of five-millimetre chips — gravel or crushed stone — to use as a mulch around the plants. Whatever kind of rock mulch you use, however, the material should blend, rather than contrast, with the surrounding rocks.

• The ideal location is a gentle slope protected from strong winds.
• A sunny site is best for the majority of plants, but dappled sunshine coming through a tree several metres away is acceptable — and even beneficial during very sunny, hot weather.
• Do not build a rock garden beneath trees that cast heavy shade, or in other shady areas, unless you plan to grow only woodland plants. Too much shade from nearby trees can be reduced by cutting off lower branches and thinning upper growth.
• Dig out all perennial weeds on the site.

• To provide drainage, dig trenches that slope down to a lower level. Make them about 45 centimetres (18 inches) deep and one to two metres (three to six and a half feet) apart.
• Fill the bottom half of each trench with large stones, broken bricks, or rubble. Then place a layer of upturned sod (or several centimetres/inches of gravel or crushed stone) on top.
• Finally, fill up with soil. Sandy soil (or other types of soil that do not require drainage) needs to be dug over only lightly before the rocks are laid.

• When the weeds are cleared and any required draining dug, place rocks along two sides of the prepared ground to form an L-shaped outcrop. Use the largest rock as the corner, or keystone, of the L. Employ progressively smaller rocks to form the two arms of the L, with the final rocks almost disappearing into the soil. The result should give the appearance of an outcrop of rock protruding from the earth, with a much larger mass of rock below.
• For good drainage place the rocks so that joints line up horizontally and vertically.
• Take care to set the rocks firmly in position.
• When all have been properly placed, fill the space between the arms of the L with free-draining soil. For this purpose, prepare a mixture of two parts five-millimetre rock chips, one part loam, and one part compost or leaf mould. Shovel this mixture inside the L until it is flush with the tops of the rocks. Then firm it by treading lightly. The mixture will settle; so keep some in reserve for adding later.
• After about 10 days (earlier if there has been heavy rain), the soil will have subsided and can be brought to the proper level with the mixture that was held in reserve. Now, rake the surfaces flat.
• Finally, apply a mulch layer of five-millimetre rock chips, a few centimetres/inches deep. Rake the chips flat.