Cornflower Plants

Cornflower plants are part of the Aster or Sunflower family.

Cornflower plants (Centaurea cyanus), also called bluebottles or bachelor's buttons, are herbaceous plants native to the Mediterranean region, but naturalized in the United States. They frequently occur in disturbed sites such as fields and along the sides of roads, but occur randomly and generally do not last long. They work well in gardens as border plants or as cut flowers.

Identification

Mature cornflower plants reach between 12 and 36 inches tall and grow in an erect, solitary form. They have narrow green stems that are covered in a thick coating of white hair when the plant is young. The narrow, lance-shaped leaves vary in size from 1.6 to 4.6 inches long; they have a thick grayish-white coating of hair on their lower surfaces and sharp, pointed tips. Some leaves may have toothed margins. The flowers grow from the ends of the branch tips, and each plant produces multiple blossoms. The flowers vary in color from pink to blue, purple, red or white. Oval-shaped seed pods follow the blossoms.

Conditions and Cultivars

Cornflower plants prefer full sunlight and can grow in a variety of different well-drained, moist soil types, preferably with a pH level between 6.5 and 7.0. They are tolerant of hot and dry weather, but do better with regular watering. They are available in a number of different cultivars such as Snowman, which grows between 18 and 24 inches tall and yields white blossoms, and Garnet, which grows between 12 and 18 inches in height and produces deep burgundy blooms. Cornflower plants are hardy in United States Department of Agriculture hardiness zones 3 through 8.

Growing Cornflower Plants

Cornflower plants grow easily from seeds. You can start them indoors during early spring if you live in a cold climate and transplant them when the soil warms, or plant them outdoors in fall or spring in warmer locations. Plant the seeds around 1/8 inch in the soil when the soil temperature is between 60 and 70 degrees Fahrenheit. They will germinate between a week and a month after planting. The seeds have around an 80 percent germination rate, according to the Texas AgriLife Extension. They grow quickly and aggressively once planted. Taller plants often fall over when they get to around 3 feet tall and may need to be staked. Deadhead spent blooms to encourage continued blossoming.

Pests and Diseases

Bachelor's button flowers are susceptible to attacks from aphids. These small insects drain sap from cornflower plants, causing leaf distortion. They also exude large amounts of a sticky substance called honeydew. A thick black fungus called sooty mold grows on the honeydew deposits. Diseases such as rust cause brown spots on leaves, while downy mildew creates moldy, discolored spots on cornflower foliage. Several other diseases that infect cornflower plants include stem rot, verticillium wilt, powdery mildew and southern blight.

References

• Kansas Wildflowers and Grasses; Bachelor's Button; Mike Haddock; March 2009
• University of Illinois Extension Hort Answers: Bachelor's Button
• Flower Garden News: Cornflower
• Fine Gardening: Centaurea cyanus
• Texas AgriLife Extension: Cornflower/Bachelor's Button
• University of Illinois Extension Hort Answers: Aphids

Resources

• Michigan State University Extension; Centaurea Disease Problems; November 1999