Filled with alpine flowers and woodland plants, rock gardens are a wonderful way to enjoy wild plants that traditionally grow in habitats such as deserts and mountains, says Jody Payne of the New York Botanical Garden.
Rock gardens are easy to build, and you can adapt them to small or large spaces using an innovative technique called crevice planting, which means placing a plant into a narrow space between two rocks. As an added bonus, since rock garden plants have evolved to survive in extreme conditions, they require very little care. Just water occasionally and you're all set.
Rock gardens can be planted in troughs using scree, a soil mix with high mineral content. Scree contains:
- Turface: a double-fired clay used on baseball diamonds, which provides excellent drainage and makes the soil mix lighter.
- Grit: a larger-sized sand, available in varieties from fine to medium to coarse.
- 1/4-inch pea gravel: pebbles that are slightly larger in size than grit; can be found at local quarries.
- Greensand: mineral often used in organic gardening that acts as a slow-releasing source of nutrients.
- Potting soil (without perlite) or peat
The soil mix should vary according to the plants used, with a basic proportion of approximately three-quarters mineral to one-quarter potting soil or peat.
Begin by selecting two rocks that fit together nicely. (Gneiss, schist, limestone, or tufa are good options.) Apply less than a 1/4-inch of potter's clay to the inside of each rock.
Unpot plant and wash roots in water. Place roots over clay and sandwich between both rocks. Bring the two pieces together tightly, and place in trough filled halfway with scree. Add other plants as desired, washing roots in water. (Tip: Vary the height of your plants by using rock in the troughs for a dynamic composition that will look lovely all season.)
Once the trough is planted, add scree mix around plants, taking special care to position the crown of the plants just above the scree. Fill trough to top. Water thoroughly and add a small amount of coarse sand. Close crevice with a little extra clay (even when the clay looks dry, it will hold moisture and nutrients for the plant). Use additional rocks and plants to finish planting trough.
Plants can be found at Evermay Nursery, Oliver Nurseries, and Wrightman Alpines. Turface is available at most lawn and garden centers. Greensand can be found wherever organic soil amendments are sold. For more information on rock gardens, visit the North American Rock Garden Society.