Choose your rocks
The type of rocks you use will depend on your budget, available space, colour preference and overall garden design you have in mind. Local quarries are a great source for buying rocks that will blend into your landscape. If you’re looking for imported rocks in various sizes, visit a landscape supplier or garden centre.
Before your rocks are delivered, decide where you’ll be placing them and dig a hole for each rock. The idea is to bury half the rock in the ground. Long-rooted alpine plants will appreciate the buried portion of the rocks to cool their roots. The rocks should also be titled back into the soil on a slight angle to allow water and rain to run along the rocks, instead of directly down the slope, which will cause erosion, says Gallagher. “The larger rocks act like a retaining wall for the smaller material in the garden.”
The perfect soil for rock gardens is one that retains moisture, but has good drainage. After the stones are placed, add a mixture of vermiculite, perlite and peat moss into the planting pockets between the rocks. Soil that won’t drain, such as clay, should be avoided.
Decide what to plant
When choosing the plants, consider their proportion to the size of rocks in your garden. If you’re using large landscape rocks, use slow-growing plants such as Dwarf Alberta Spruce, Little Giant Globe Cedar, Goldflame Spirea, Dwarf Hemlock, Abbotswood Potentilla, Blue Star Juniper, Nikko Slender Deutzia, or boxwood. For cascading plants, try Wintercreeper Euonymus, Rockspray Cotoneaster or Siberian Cypress.
For gardens designed with smaller rocks, use a variety of annuals, perennials and miniature bulbs. Tulips, daffodils, snowdrops and crocus will add colour in the spring. For summer interest, try Rock Cress, Creeping Phlox, bellflowers, Scotch and Irish Moss, Creeping Speedwell, candytuff, Dwarf Primula, lobelia, portulaca or alyssum.
For rock garden beginners, Thivierge recommends Hieraclium villosum, Primulas, Aguilegias and Drabas. Her favourite plants are Cyclamens, because of their delicate flowers and foliage, Aguilegias, because of its height and colours, and Pulsatillas, Lewisia cotyledon and Gentianas, because of their brilliants colours. To create a garden with four seasons of interest, combine evergreens with deciduous shrubs, and plants with horizontal and vertical habits to create contrasting textures and height. Gallagher recommends dwarf evergreens as the best choice for interest in the garden year round. Ornamental grasses are also an excellent choice for adding interest.