Cornflowers (Centaurea spp.) are small, free-flowering annuals with delightful sky-blue flowers. The cornflower plant is easy to grow by seed and makes a long-lasting cut flower, even retaining the blue color when dried.
Cornflowers Facts to Grow From Seed
Cornflower seed is widely available in garden centers and seed catalogs, where it is commonly referred to as bachelor's button and occasionally by other names, such as bluebottle flowers. The cornflower is an annual flower that's ideal for a summer flower garden, growing from one to three feet tall, depending on the variety. As an annual, it is suitable for all USDA zones.
Identify Traits of a Cornflower Flower and Plants
The cornflower foliage is spindly and nondescript. It is composed of one-inch-long, lance-shaped leaves. Cornflower plants are grown primarily for the blue flowers. The cornflower flower is a one- to two-inch round cluster of numerous tiny flowers. The blue flowers bloom from early summer until the first fall frost.
How to Plant Cornflower Seeds
In the spring, cornflower seed can be sown directly in the garden as soon as the ground can be worked. Cornflower plants are not picky about soil, but benefit from a bit of compost being worked into the planting area. You need to plant the seeds about a half-inch deep and six inches apart in a sunny or partly sunny location. After the seeds sprout, thin the weaker seedlings, leaving the rest spaced about 12 inches apart.
How to Use Types of Cornflower in Your Landscape Design
Cornflowers are typically combined with other annual flowers or mixed in with larger perennial species as an attractive filler. You can plant them in wildflower meadows, cottage gardens, and perennial borders. Cornflowers are one of the best species to include in beds for cut flowers.
Include Cornflower Flower Varieties in Wildflower Mixes
If you wish to sow cornflower seeds in with wildflowers, you can simply add cornflower seeds to a wildflower mix. You can then broadcast the mixed seeds over a large area.
Care of Cornflower Plants
Cornflowers are very low maintenance plants, although they do need regular irrigation to thrive throughout the summer. Removing the flowers as they fade will help to encourage repeat blooming. By late fall, the spent stalks can be pulled out or cut to the ground.
Allow Cornflowers to Self-Seed
While cornflowers are annuals, this flower is self-seeding. When you establish a bed or field, cornflowers will self-sow year after year. If you allow some seed heads to dry on the plants at the end of the growing season, they'll self-sow for more cornflowers next year. The flowers may even need to to be thinned out to avoid overcrowding.
Cornflower Pests and Diseases
Cornflower pests and diseases are of minor concern. Aphids may show up, but rarely become an infestation and can be dispatched with a sharp jet of water or an insecticidal soap spray.
Powdery mildew can occur in hot humid places and is best dealt with by destroying any plants that become badly infected to prevent its spreading. You want to avoid overcrowding and growing the flowers too closely together since this can result in stem rot or stem rust.
Cornflower Plant Medicinal Purposes
Cornflower is occasionally used for medicinal purposes, especially the flowers, which are used as an eyewash. If growing cornflower for this purpose, use the common species (Centaurea cyanus), rather than one of the hybrid cultivars, and harvest the flowers in the morning just after they open. This allows you to harvest the most nutrients and energies from the plant.
Cornflower Varieties for Gardens
Cornflower has been developed into a number of named cultivars and hybrids that offer different colors besides the traditional blue form. Mixing different colors in a single planting makes the colors more impactful.
- 'Burgundy Beauties' is a mixture of deep purple and whitish flowers on plants about three feet tall.
- 'Dwarf Blue Midget' is a blue flowered form that reaches only 12 inches tall.
- 'Florence Mix' is also just 12 inches tall and has a mix of white and pink blossoms.
- 'Almost Black' has deep purple-burgundy blossom on plants to three feet tall.
- 'Gold Bullion' features golden leaves with maroon center lavender colored flowers, and the plant grows up to two feet tall.
- 'Amethyst Dream' has flowers that are a deep purple and the plant grows up to 20 inches tall.
Choose Cornflowers to Grow in Your Garden
Cornflowers are not large and spectacular, but they are brightly colored and cheery-looking. Cornflowers are priceless as cut flowers and an ideal addition for your naturalized meadow plantings.