A rock garden is essentially a small raised bed made of rocks and populated with plants that need plenty of sunlight and well-drained soil. Given space restrictions a rock garden is preferable to a conventional garden, and the fact that they require relatively little water, fertilizer, and maintenance is a bonus. Furthermore, the rock garden should feature hardy, long-lived, but attractive perennials, dwarf shrubs, and hardy bulbs that can tolerate a wider range of soils and climatic conditions than most conventional gardens.
The Basic Components of the Rock Garden
Having decided on a location and settled on a size and form for the rock garden, the project can proceed with the gardener laying a base of rocks and soil that can be built upon. Most attractive rock gardens include a natural setting that blends with a pile of stones on level or slightly raised ground. You are lucky and it will be much easier if you can develop a rock garden on property that already has strewn natural stones, large boulders, and maybe a small hill. But that's a dream. Furthermore, even if your land is flat, with a little imagination you can create a great artificial rock garden.
A sufficient number of large flat stones should be included to allow one to walk through the garden or stand while doing maintenance there. These must be deeply imbedded to provide secure footing and preventing erosion and run-off. Rocks that you add to the space should be weathered native stones that establish a natural look.
Start at the base of the slope you have carved out and work up from there. Place the rocks in a natural position with layers on the same level as existing material. Tip the stones toward the back to cause water to run into the soil around the roots of your plants rather than off the hill. To maintain a natural look, rocks should be irregularly placed and be of irregular size. Be sure not to place all large rocks at the back and the small ones in the front, but rather mix them up somewhat without following a repetitive, predictable pattern. Rocks should be buried to a sufficient depth to keep them stable—at least one third of their size should be below ground. If only laid on the surface, they will shift during heavy rain and the frosts and freezes of winter.
Selecting Plants for the Rock Garden
Plants for the rock garden should need a minimum of care while tolerating harsh growing conditions. First, dwarf evergreen shrubs may be used to give a permanent quality to the rock garden. Hardy native ferns, perennial flowering plants, miniature roses, and spring-flowering bulbs add interest and color. Avoid the use of large masses of plants or those with oversized, intensely colored blooms. Annual flowers should be used sparingly, especially such common species as petunias, or the large-flower varieties of aster, marigold, or zinnia, many of which will self-sow and may squeeze out other plants.
Suitable dwarf conifers for the rock garden include Abies balsamea ‘Hudsonia’ (Balsam Fir), Juniperus horizontalis (Blue Pygmy Juniper), and Picea abies 'Little Gem' (Norway Spruce). Consider the following perennials for a wide array of color, texture, and form:
- Artemisia schmidtrana (silver mound)
- Festuca ovina var. glauca (dwarf blue fescue)
- Oenothera speciosa (showy evening primrose)
- Stachys byzantina (lamb’s ear)
- Dianthus gratianopolitanus (cheddar pink)
- Phlox subulata (moss phlox)
- Sempervivum tectorum (hens and chicks)
- Delosperma cooperi (hardy ice plant)
- Helianthenum nummularium (rock rose)
- Campanula garganica (Adriatic bellflower)
- Gentiana newberryi (Alpine Gentian)
- Saxifraga bronchialis (saxifrage)
- Sisyrinchium brachypus (blue eyed grass)
- Sedum spurium (dragon's blood)
- Iberis 'Snowmantle' (minature candytuft)
For seasonal interest in the rock garden, consider planting bulbs such as miniature daffodils (Narcissus asturiensis), scilla, snowdrops and other ‘small bulbs’, Iris pumila (dwarf bearded iris plant) and species tulips (Tulipa species, such as Tulipa humilis 'Eastern Star') and annuals like California poppy ‘Rose Chiffon’ (Eschscholzia californica) and Portulaca grandiflora (moss rose).
Routine Maintenance for Rock Gardens
It is important to provide adequate good soil in the pockets around and between the rocks. Because your rock garden's soil should be well-drained, you will want to mix one third sand, one third garden soil and one third humus. You may need to add more sand for those plants that require the most perfect drainage or more humus for those plants that prefer acidity and root moisture.
Watering is usually not a problem in rock gardens, but it is important to water the area thoroughly when first planted. Use care not to use a harsh stream of water. You may find it better to apply a little water at a time even though it takes longer than otherwise. You should find that your plants thrive. Avoid using powerful fertilizer of any kind so as to avoid growing large plants—in a rock garden smaller plants are better.
Most rock plants benefit from an occasional application of manure or compost. Routine maintenance will include trimming back leggy plants, dead stems, and spent foliage. Remove weeds from the rock garden’s nooks and crannies so they don’t crowd out plants. Check plants regularly for diseases and insects, in particular slugs that seek shelter among the rocks. Finally, plants that have become root bound or too large for the available space should be promptly divided.
Shirley Hollis - Shirley is a professional sociologist and was a college professor until her health drove her from the classroom. Now retired she divides ...
