Dianthus is an ideal rock garden plant, a great edging plant and perfect for cottage gardens. You may wonder how a single plant can be so versatile. The answer is because there are so many varieties of dianthus. Some are low-growing, making them perfect as an edging plant. Others, such as the common Sweet William, are tall plants that will work well at the back of a border or grown in combination with taller plants.
Plant dianthus among roses, coreopsis, lavender, lamb's ears, red valerian, aster and hollyhock to add season-long colour to the garden. Deadhead, or cut off the faded flowers, to encourage this plant to continue to bloom, but do let the last round of flowers set seed. Allow these seeds to drop into the garden. Dianthus are either annuals or short-lived perennial plants that will come back from seed. A perennial plant is one that comes back from its own root system year after year.
An annual is a plant that grows, flowers, sets seed and dies in one growing season. Verbena, New Guinea impatiens, stock and snapdragon make good annual companion plants for dianthus. Verbena is an ideal trailing plant for growing underneath taller varieties or using as the spiller in a container combination that includes dianthus. A spiller is a plant that spills over the edge of the pot. New Guinea impatiens will tolerate more sun than the regular varieties of impatiens; however, growing them under or in front of the taller varieties is recommended. Stocks and snapdragons combine well with shorter varieties of dianthus, unless you are growing the tall varieties of snapdragon that are used as cut flowers. That variety will look better grown among taller varieties of dianthus.
Low-growing dianthus looks good under or right in front of shrubs. Ninebark, lilac, forsythia, viburnum and boxwood are ideal companions. Boxwood is often used in formal gardens to create edgings. Place low-growing varieties of dianthus around the outer edge of the boxwood shrubs. This will add colour and fragrance to the garden. The low-growing varieties of dianthus make an ideal ground cover. A living mulch conserves soil moisture, helping to keep the shrub's roots cooler, and chokes out weeds. Since dianthus is short-lived, the seeds will scatter and grow in new places as the shrub's base enlarges with age.
Clematis, bittersweet, honeysuckle, maypop and wisteria add a vertical dimension to the garden and create privacy. Many of these plants prefer that their roots remain cool and moist, even though they prefer to grow in full sun. Dianthus is the answer. Plant taller varieties closer to the base of the vine, then add other varieties to create a stair-step effect, or use low-growing varieties as a ground cover. Dianthus flowers come in many colours, so do consider this factor when pairing them with flowering vines.