Carnations are flowering plants native to Europe and Asia. They are one of the most popular commercially produced cut flowers, and are prized for their attractive ruffled flowers. They are a traditional gift of love and friendship on Valentine's Day in America. Carnation flowers bloom in late spring through midfall, and each bloom lasts up to two weeks. Colors of white, pink, purple, red, orange and yellow are common. Carnations are typically grown as annuals, although many species are actually perennials and can be grown for many years with the proper care.
Plant carnation seeds or seedlings 10 to 12 inches apart in a prepared garden bed in late spring or early summer. Choose a planting site that receives full sun to partial shade, and that has well-drained, fertile soil. Use a garden tiller to mix in a 2- to 4-inch layer of organic compost prior to planting for the best results.
Water carnations thoroughly after planting to settle the soil, and then water once per week during the spring and summer months any time the rainfall is less than 1 inch. Do not over-water because this will cause the foliage to turn yellow.
Apply a 1- to 2-inch layer of organic compost to the soil surrounding carnations each spring. Follow with a 2-inch layer of organic mulch. But keep a 2- to 3-inch perimeter around the stems clear. Carnation plants require good air circulation around the stems and can suffer from disease if mulched too heavily.
Fertilize carnations once every six weeks during the spring and summer using a 20-10-20 NPK liquid fertilizer according to the manufacturer's directions. Water thoroughly after application to ensure proper distribution of the nutrients.
Remove spent flower blooms on tall varieties as soon as possible to promote new blooms and extend flowering time. Cut back mounding varieties to within 6 inches of the soil line after blooming to encourage a second flowering. Pinch off any flower buds that grow on the sides of the stems if you want cut flowers, and leave only one bud at the top of the stem.
Cover annual carnations with a light organic mulch in the fall to protect them from winter temperatures. In many cases, they will emerge again the following spring. You also can bring plants or cuttings indoors during the winter, place them in a cool, sunny window, and then replant outdoors in the spring.