How to Build a Rock Garden


Creating the Base

Lay down a 15 cm (6 in) layer of drainage material such as coarse rubble, pea shingle, broken bricks or stones. If you removed turf from the area when you prepared the site, lay this upside-down over the rubble to prevent the soil from clogging the underlying drainage material. If you do not have any inverted turves, spread a polypropylene sheet over the area. Puncture this with holes at regular intervals to allow water to drain through.

Cover the turves or polypropylene sheet with a 23-30 cm (9-12 in) layer of soil. This may be newly purchased top-soil or good soil from elsewhere in the garden. A standard mix of sharply drained compost (read the recipe here) should be used in the areas where plants are to be grown.

Stone is very heavy and you must always take great care when moving it so you do not injure yourself.

* Use gloves and sturdy boots to protect your hands and feet and never try lifting anything that is too heavy for comfort.

* Larger rocks may be moved using rollers or dragged over in slings made from sheets of polythene.

* Avoid using wheelbarrows, as these tend to tip over very easily; use a trolley with pneumatic tyres instead.

* Large rocks may need to be manoeuvred into their final positions using a block and tackle, and a crowbar used as a lever for final adjustments.

Placing the Rocks

Before beginning to place the rocks, it is useful to mark out the approximate positions of larger rocks first to avoid any unnecessary work. Use a length of rope and pegs to indicate the shape of each main rock outcrop.

Start with the larger good pieces; these will act as keystones which will set the character of the entire design and from which each outcrop will be developed. Place the largest of these stones first, and then set other pieces around it so that they flow naturally to form the outcrops. Make sure that you take into account the natural features of the rock; any strata lines should all run in the same direction and at the same angle. Sometimes a piece of rock will just look wrong. Put it to one side; there will be a place for it later on.

The stones may be placed to create a number of planting opportunities, such as narrow crevices between two adjoining pieces, terraces or nooks. Using different rock placements will allow you to provide a wide range of planting conditions so that you will be able to grow a variety of species.

Using a spade, dig out a hollow for each large piece of stone so that about a third to a half of it will be buried; this will ensure that it will remain absolutely stable. Lever it into position using a crowbar. Make sure that the rock tips back slightly so that rainwater will run off the back of the rock into the bed, rather than drenching the plants below. Support the stones by wedging smaller stones or rubble underneath.

Continue to add further stones to extend the outcrops, using enough rock to make the structure look realistic, whilst leaving enough room for planting. Take your time in positioning the pieces, making a regular visual check as construction progresses.

When you have finished positioning the stones, infill underneath and in between the rocks with garden soil, treading it down firmly to make sure that each stone is firmly seated and that there are no air pockets. Add a layer of sharp compost (soil, peat and grit) to the surface of the rock garden and around each of the stones.