Building a Rockery

The best time to build and plant the rockery will be in the early spring, when all new growth is starting. This will give the newly planted rockery a chance to establish itself.
When choosing a site for your rockery – it’s best to go for somewhere that is mostly sunny and that gets at least half a days sunshine in the winter.  Remove your grass in sections and keep to the side as you will need this later. (if you are building your rockery on a non-grass site, then just ignore this step!)
If your site is on flat ground – use an eclectic mix of old bricks, broken crockery and anything else small that you can salvage.  Make sure it doesn’t contain toxins that will leak into the ground – eg plastic.

http://www.gardenjoy.co.uk/dirrockeryplants.htm

Lay the turf upside down over the rubble and firm down. Fresh soil will be needed to raise the level further still. If possible, this should be mixed with coarse grit (4mm to 6mm is ideal) and some generous handfuls of bonemeal or a similar slow-release fertiliser.

if it is possible to source local rock, strategically place this around your site (ideally sandstone or granite).  It is important to cover at least half the rock so that the plant’s roots stay cool in summer.  Ensure that the strata (natural lines of the rock) are in line with each other and that the rocks tilt slightly back into the slope.

Another important element is gravel – ideally that matches your rock! (but I wouldn’t worry too much about this)  It actually prevents the soil drying out and the little plants being splashed with mud during heavy rainfall.
It’s advisable to let your newly built rockery settle for a bit before planting, incase there is any movement of your bigger items.  You don’t want to have to replant!
What type of plants to choose taking into consideration soil types.
Dwarf confirs, shrubs, alpine plants, bulbs
It is best to start at the base of the slope and work upwards in layers leaving planting pockets between the rocks. Alpine plants are used to growing in small cervices amongst gravel and shale which is the environment that you are trying to create.

Rockery plants need soil which is both water and air permeable. Rockery plants do not thrive in water logged conditions, e.g. in clay rich soils -If you are to grow rockery plants in clay soils then you must ensure that it is well drained -This can only be achieved by using compost.

What kind of plants should you plant in your rockery?

There are two kinds of plants you should consider;

*Plants for dry positions with plenty of sun
*Plants for shady positions with moist soils and high humidity

These two groups can be combined together in large rockeries. Large rocks, artificially designed hollows and sunken paths will provide shay spots that can be planted with varieties that prefer cool positions. A rockery with water will be very humid while beds edged with bushes or trees are not ideal for rockery plants because of the shade and dry conditions.

Dwarf Conifers – dwarf juniper, cypress, spruce or pine would be an ideal basis for your rockery.
 

Shrubs – Daphne, Berberis, Rock Rose, Parahebe
Perennials – Persian Stone Cress, Cranesbill, sandwort, alpine pink, alpine phlox, violet, snow glory, miniature iris, crocus.

Wildlife In A Rockery
Many creatures colonize a perfectly balanced rockery. The ecological equilibrium will be determined by the conditions of the position, and by the presence of suitable plants and rocks. Rockeries, garden ponds and drystone can all develop into balanced biotypes that can support wildlife. Creatures such as slow worms or lizards, frogs and toads will colonize damp hollows and beside pools of water. Birds may build their nests on cushion plants and spaces between rocks or stones. Shrews look for shelter and food in the rockery and build their homes there.
Planning a rockery

Careful planning is necessary if you want rockery garden to captivate the eyes off passers by. You will need to design the landscape, prepare the soil and select the right position.

Landscape design

You can use the soil that is excavated when a house is being built or landscape modeling. Soil that is left after digging out a pond is ideal for creating a rockery.

Choice of position

You must select an ideal position to prepare the soil. You must scrutinize all areas in your garden, paying particular attention to sloping positions as they are an ideal terrain for rockery design. Level areas close to a garden or patio are also suitable for rockery plants.

Soil preparation

Soil preparation is essential if you are going to have a beautiful rockery. Determine the soil structure by using your hand. Sand soil sifts easily through the fingers, loamy soil stick while the clay soils are normally very hard and lumpy.

You can use a tester kit to determine the numeral content of the soil or alternatively you can send your garden soil to a specialist who can test it for you, although this may cost you.
Soil that has high lime content is most suitable for rockery plants. The lime factor determines the pH factor of the soils. Remove all weeds from the soil before you plant the rockery plants and ensure that the soil is well drained.

If the soil is too compacted then there is a great need to install a drainage layer. The garden compost and a small quantity of hoof and horn help to improve the quality of the soil.