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Rock and Alpine Gardening Using Annuals |
By Karen Panter, Horticulture Agent, Commercial Greenhouse, Colorado State University Cooperative Extension
Many of us have a sloping or rocky (or both) area in our landscapes that requires some extra attention. One of the ways to build an attractive garden area is to use rocks and low-growing plants in a rock garden. There are many annuals that work well in this type of setting.
Let's assume that all the preparatory work in the garden has been done. This prep work should have included using rocks of the same geological type for the best effect. It should also have included soil amendments, such as addition of organic matter, and thought as to how the garden will be watered. Most alpine/rock garden plants must have good drainage.
Some rules of thumb for planting rock/alpine gardens include using many different types of plants, including annuals. Each type of plant should be repeated several times within the garden to create a more natural effect. Try not to overplant the garden so that rocks and mulch are covered up quickly during the growing season. Plant species that are low-growing and have a clumping growth habit.
Most of the plants that are best suited for rock gardens are perennials. However, there are a few annuals that fit in quite well with this type of landscape. Some of them include: dianthus (Dianthus Barbados), allysum (Lobularia maritima), portulaca (Portulaca grandiflora), and vinca (Catharanthus roseus).
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Dianthus is available in shades of white, pink, and red. Dianthus is in the carnation family and has the clumping habit that works well in rock gardens. This species also likes cool nights and bright, sunny days so it's a natural for our Colorado summers. If dianthus is planted in a protected area, it frequently will overwinter. It also benefits from deadheading during the summer to keep it blooming. |
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Alyssum is a very fragrant (some would say pungent) mounding plant. Flowers are very small and white. It is excellent as a border or accent plant for rock gardens. It prefers a sunny, dry, and well-drained location. It has a tendency to reseed itself each year so you may find tiny allysum seedlings each spring. Allysum is a very good choice for rock/alpine gardens because of its mounded behavior. It will bloom all summer long. |
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Portulaca, or moss rose, is a very showy annual that is available in a rainbow of colors. A very low growing plant, it is perfect for warm, dry areas such as might be found in a rock or alpine garden. The flowers of annual portulaca are interesting in that they close up at night. This is tough plant that thrives on neglect. It also has a tendency to reseed itself, so look for tiny seedlings in your garden each spring. |
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Annual flowering vinca is another plant that likes dry, warm conditions. Available in white as well as shades of pink and red, the annual type of vinca forms dense clumps with very showy flowers. Many of the white varieties have centers of other colors, adding to their attractiveness. This is another plant that benefits from deadheading during the growing season to keep it blooming freely. |
With a little advanced planning and careful selection of plants, your rock or alpine garden can be full of color all summer long.
Photos: Judy Sedbrook.
