Building a Rock Garden
Once the rocks have been chosen, prepare the site by excavating to the proper depth. Make sure you remove any weeds or lawn grasses now: You don't want them reappearing later between two heavy rocks where you can't get to them.
Most alpine plants require perfect drainage. If your soil is naturally heavy, put down a drainage layer of six inches of gravel or crushed rock. Cover this layer with landscape fabric or two inches of sand so the soil you add later won't percolate through. Unless the soil taken from the excavation already drains perfectly, mix it with an equal quantity of sand. If you don't intend to grow alpine plants, simply add about one-quarter compost or peat moss to increase the soil's organic content. If you intend to grow mostly alpine plants, check the soil's pH and amend it with ground limestone if necessary; alpine plants tend to prefer neutral to alkaline soils. Only a few rock garden plants (heathers and dwarf rhododendrons are among them) need acid soil.To "anchor" a rock garden to its landscape, consider adding a few minor rock outcrops in peripheral areas. Also, add to the base of the rock garden a flat area of gravel or crushed rock in the same shade as the dominate rock. This is known as a "scree garden." This will help prevent lawn grasses from invading the garden, and the effect will appear quite natural, as if bits and pieces of broken rock had fallen off the rock outcropping over the years.
In regions where droughts are frequent, consider adding an irrigation system from the outset. The simplest method is burying a perforated garden hose just below the surface of the soil: It can then be attached to a supply hose whenever watering is necessary.
In the final section, we'll show you how to care for your rock garden.