Eagle Lake Nurseries Gardening Tips April 2008 Rock Gardens A rock feature makes an interesting addition to a garden, and time and effort spent on such a project is well rewarded. The size of your rock garden should be in proportion to the space available, but be daring – a large feature rock adds tremendous character! A sunny slope with at least 6 hours of sun, preferably in the afternoon, may be incorporated into your plans, or if the area is flat a raised berm adds interest and drainage. Consider installing a water feature or even a dry stream bed, both pair well with a rockscape. Alpine plants grow naturally in such areas, and do not require a lot of water once established, an advantage in our climate. When preparing the soil for planting bear in mind that alpines usually like a ‘leaner’ soil with a gritty texture and excellent drainage. Compost and peat moss are good for amending a clay soil but avoid too much manure: an alpine soil mix is available from some landscape companies and is often worth the initial expense. The site must be clear of weeds, so consider fallowing the area or even solarizing with thick clear plastic before planting. Large rocks are needed as the skeleton of your structure, and these may have to be installed with a backhoe or bobcat. Try to avoid scattering the rocks randomly; rocks of similar size and colour should be grouped together to recreate the natural rock strata of mountain landscapes. It is necessary to bury up to half of each rock in the soil for a firm foundation to the garden. It may be a good investment to lay thick, good quality landscape fabric, covered with 3” of mulch: either gravel or bark mulch is suitable for the job. Plants are installed by pulling back the mulch, cutting an ‘x’ with a sharp knife, planting, watering, and then replacing the fabric and mulch around the new plant. Be creative when selecting plants! Try to incorporate some larger plant material to provide balance, and include evergreen specimens and those with special winter interest. Check the mature size of the shrubs as a dwarf selection may suit the site better – such as a ‘Mops’ or ‘Slowmound’ mugo pine instead of the original mugo which may grow to 10ft. tall. Local garden centers have a good selection of perennials for rock gardens, and local garden clubs, in particular the Calgary Rock and Alpine Garden Society, are an excellent source of advice. Some herbaceous perennials to try in your rock garden: Aurinia montanum Androsace sarmentosa Aguilegia alpine Antennaria spp. Arabis caucasia Arenaria Montana Armeria maritime Artemesia spp. Aster alpinus Aubretia deltoidea Campanula carpatica/cochlearifolia/poscharskyana Cerastium tomentosum Dianthus spp. Gentiana spp. Geranium sanguineum Gypsophilia repens Iberis sempervirens Leontopodium alpinum Lewisia cotyledon Papaver alpinum Penstemon spp. Phlox subulata Potentilla spp. Primula auricola Pulsatilla vulgaris Sagina subulata Saponaria ocymoides Saxifraga spp. Sedum spp. Sempervivum spp. Silene spp. Thymus spp. Veronica incana/repens/teucrium Viola spp. Some of the smaller perennial grasses are suitable for inclusion in rock garden plans – try ‘Elijah’ Blue Fescue or Bulbous Oat Grass. Last of all, do not forget to plant bulbs, such a welcome sight after the long winter months! Crocus, Siberian squill, grape hyacinth, dwarf iris, snowdrop, Chionodoxa, Allium, dwarf daffodlils and species tulips are all hardy in the Calgary area. Connie Webb Eagle Lake Nurseries Ltd.