Centaurea cyanus–commonly called Bachelor’s button–is a hardy annual and member of the Centaurea genus which includes dusty miller and mountain bluet. Bachelor’s button is one of the most popular annuals with its bright blue tufted round blossoms.
Centaurea cyanus is a bushy plant with grayish-green, lance-shaped leaves and dense thistle-like flower heads. It grows best in full sun in well-drained soil. There are tall varieties that grow to 36 inches tall and dwarf varieties.
Bachelor’s button is used for bedding, containers, and cut flowers—both fresh and dry. They are effective when massed for color in beds and borders, in foregrounds or backgrounds.
Get to Know Bachelor’s Button
- Plant type: Annual
- Growing zones and range: Zones 3-9
- Hardiness: Tolerates light frost
- Height and width: 12 to 18 inches (30-45cm) tall; 10 to 12 inches (25-30cm) wide
- Foliage: Lance-shaped leaves 4 to 8 inches long; lower leaves with pinnatifid lobes and wooly-hairy beneath; lacy effect
- Flowers: Flowerheads 1 or more inches across with violet blue inner florets
- Flower colors: Often blue flowers but also shades of pink, purple, and white; tufted, rounded blossoms
- Uses: For beds, borders, cottage gardens; short varieties in containers; excellent cut flower
- Bloom time: Early to mid-summer
- Common name: Bachelor’s button, annual cornflower
- Botanical name: Centaurea cyanus
- Family: Asteraceae
- Origin: Mainly in Europe and Mediterranean
Where to Plant Bachelor’s Button
- Grow bachelor’s buttons in full sun.
- Plant Bachelor’s button in humus-rich garden soil; it will grow in average, well-drained garden soil.
- Prepare planting bed by turning under aged compost to a depth of 12 inches (30cm)
Bachelor’s Button Uses
- Plant bachelor’s buttons in beds and borders.
- Excellent for cutting.
- Bachelor’s buttons attract birds
- Interplant with yellow or orange-colored annuals such as California poppies and Gazania.
- Dwarf forms are well suted for containers.
When to Plant Bachelor’s Button
- Start seed indoors 8 to 10 weeks before the last frost.
- Sow seed outdoors in Zones 5 to 8 two weeks before the last spring frost Do not sow seed in weather colder than 25°F (-4.4°C).
- Sow seeds outdoors in autumn in Zones 9-10 for spring blooms.
- Set out seedlings after the last frost in spring. Set out seedlings after hardening them off for several days in the shade.
- Make successive sowings to prolong the bloom season
Planting and Spacing Bachelor’s Button
- Sow seed in flats or individual six-packs; space seeds 1 inch (2.5cm) apart; sow seed in a sterile seed starting medium.
- Cover seeds 1/8-inch deep and grow at 65°-75°F (18-24°C); seeds usually germinate in 7 days.
- Grow seedlings indoors in bright sunlight or a few inches below fluorescent light.
- Sow seed outdoors 2 inches (5cm) apart and cover them with ¼ inch of soil.
- Space bachelor’s button 10 to 12 inches (25-30cm) apart.
How to Water and Feed Bachelor’s Button
- Keep the soil evenly moist but not wet. Bachelor’s buttons are somewhat drought tolerant once established.
- Add a 9-month slow-release fertilizer to planting beds before planting.
Bachelor’s Button Care
- Keep the soil evenly moist.
- Fertilize with an all-purpose fertilizer at planting time; fertilize plants every 4 weeks during bloom time.
- Mulch around plants with aged compost.
Bachelor’s Button Propagation
- Centaurea cyanus is easy to grow from seed; sow in the fall for the earliest start or as soon as the soil can be worked in spring.
- Germination takes about 7 days at 70°F (21°C).
Bachelor’s Button Varieties to Grow
- Centaurea cyanus is the popular bachelor’s button or cornflower. A ;ist of cultivars follows:
- ‘Blue Diadem’ grows to 30 inches tall with intense blue flowers.
- ‘Blue Midget’ grows to 10 inches tall with sky blue flowers.
- ‘Florence Mix’ has blue, pink, white, and red flowers.
- ‘Frosty’ includes mixed pastels frosted with white tips of petals
- ‘Polka Dot’ includes mixed colors of red, white, blue, rose, wine, lavender on short bushy plants.
Other Members of the Centaurea Genus
- Centaurea dealbata, Persian cornflowers, is a perennial that grows to 2 feet tall and 3 feet wide.
- C. gymnocarpa, dusty miller, is a tender perennial grown for its divided, feltlike, gray-white leaves.
- C. montana, mountain bluet, mountain knapweed, is a perennial with feathery, pale blue flowers.
- C. moschata, Sweet sultan, is a half-hardy annual that needs warm weather; flowers are large and silky.