Carnations (Dianthus caryophyllus) are probably the most popular cut flower in the world, according to Dr. Leonard Perry, a horticulture professor at the University of Vermont. They are inexpensive, come in a wide variety of shapes and colors, require only basic care, and the flowers last an exceptionally long time in a vase. These perennial plants are an excellent addition to any cut-flower garden.
Native to the Mediterranean, carnations prefer mild or temperate climates with cool winters and warm or hot summers. They can be grown outdoors in United States Department of Agriculture (USDA) hardiness zones 6 through 9, according to information published by the horticulture department of Michigan State University.
Dianthus caryophyllus needs full sunlight in order to bloom well. Plant your carnations where they will receive at least six, but preferably eight to 12, hours of sunlight per day, save in the hottest USDA growing zones. Home gardeners in subtropical areas and high desert areas can place the plant where it will receive some afternoon shade. Evening temperatures should drop below 65 degrees F for at least part of the year in order for the plant to bloom.
Soil and Water
Carnation plants are a bit fussy about the type of soil they prefer. These perennials need loose, loamy soil rich in nutrients. It is also imperative that the soil drains well, according to Perry. Amend hard or poor soil with organic mulch and peat moss to add nutrients and improve drainage. Keep the soil moist, but not soggy, throughout the growing period (spring and summer). Reduce watering in fall.
Pinch back early and side blooms to promote larger, thicker flower growth. Deadhead (cut or prune) off blooms to encourage new flowers to develop. The more you cut carnations, the more they will bloom. The stems are weak, so you may have to support them with stakes if you leave the flowers on the plant.