Bachelor's Buttons Plant Profile

Mixed Cornflowers up-close
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Gardeners looking for a true blue color in a flower can’t go wrong with the old-fashioned bachelor’s button. These fully double annual flowers look like miniature carnations, only they’re much easier to grow. They are treated as weeds in some areas because of their propensity to self-seed. Nevertheless, every gardener needs at least one can’t-fail plant in the flower garden, and this lightly fragrant flower belongs in every beginner’s landscape.

Centaurea cyanus plants have been cultivated for centuries, and have picked up many nicknames along the way, including bachelor’s buttons, basket flower, bluebonnet, blue bottle, blue bow, blue cap, cornflower, boutonniere flower, and hurt sickle. The quick-growing flowers will reach a height of about 30 inches and a spread of 10 inches in all growing zones when given a bright spot. 

Botanical Name Centaurea cyanus
Common Name Bachelor's Buttons
Plant Type Annual
Mature Size 12–36 inches
Sun Exposure Part to full sun
Soil Type Well-draining
Soil pH Alkaline
Bloom Time Summer
Flower Color Blue, purple, pink, or white
Hardiness Zones 2–11
Native Area Europe

How to Grow Bachelor's Buttons

Bachelor’s buttons are as easy to maintain as they are to start.  Stake plants if they flop, which is usually more of a problem in shaded gardens. Alternatively, you can grow them among other sturdy perennials like coneflowers that will act as natural supports for the stems.

Bachelor’s buttons bloom from midsummer until the first frost, but deadheading them extends and increases the blooming. They make excellent dried flowers if you cut the blossoms before the frost nips them.

Consider adding bachelor's buttons to the ornamental vegetable garden, as their nectar content will attract pollinating insects that boost the yields of tomatoes, squash, and other plants that rely on pollinators. Bachelor’s buttons produce edible flowers, so you can include them in the kitchen garden to jazz up salads. Some describe their taste as sweet or cucumber-like. Bachelor’s buttons have a long tradition in herbal and natural medicines as an anti-inflammatory so you can include them in the herb garden too.

As an ornamental, bachelor’s buttons look pretty in wildflower gardens, and their bright blue blossoms are highly appealing to bees and butterflies. Avoid spraying any pesticides around cornflowers, even organic pesticides, which are still harmful to bees and other beneficial insects.

Popular as an inexpensive and renewable source of blue flowers in wedding bouquets, cornflowers are also welcome in the home cutting garden. Pair blue cornflowers with annuals opposite on the color wheel, like orange cosmos or yellow marigolds, to make both flowers stand out in the flower garden.

Light

Bachelor's buttons prefer full sun, but they'll still do well with a bit of shade in the afternoon.

Soil

Provide average, well-drained garden soil. Unlike many garden flowers, bachelor's buttons prefer soil on the alkaline side, with a pH of 7.2-7.8. You can add crushed limestone to garden beds if your soil is on the acidic side.

Water

Give bachelor's buttons the equivalent of an inch of water per week, especially in the hottest months of July and August.

Temperature and Humidity

When it comes to temperature, bachelor's buttons are fairly agreeable, tolerating both light freezes as well as the hottest summer days. They'll tolerate humidity, but keep a close eye on them in these conditions, as it leaves them susceptible to fungal disease.

Fertilizer

Fertilize your bachelor's buttons monthly with liquid manure or compost tea if your soil is poor.

Growing from Seed

You can buy packets of 200 bachelor’s button seeds for less than five dollars, making this a great flower choice for frugal gardeners. Even if you aren’t used to growing plants from seed, you have a high chance of success starting cornflower seed. Sow in late winter or after the first frost directly in the garden. Don't be too concerned about planting too early; Mother Nature will tell the seeds when to germinate.

Cover seeds with about a half-inch of soil. Keep the seedbed moist until germination occurs, usually within 10 days in warm temperatures. Cornflowers can tolerate some crowding, but thinning seedlings increases blooming and vigor in plants.

At the end of the season, collect the brown seed pods to sow in other areas or to share with friends. Expect more bachelor button flowers in the same site next year, as they volunteer freely. 

Varieties of Bachelor's Buttons

Most people are drawn to the vibrant blue of bachelor's buttons, but why not explore other options with this easy annual?

  • Blue boy: a vivid periwinkle blue
  • Tall double mixed colors: shades of white, pink, and blue
  • Blackball: a rare variety with deep crimson poms
  • Dwarf blue midget: blooms begin at 6 inches, and container-worthy plants max out at 12 inches