Cornflower, or Centaurea cyanus, is a hardy annual wildflower that grows quickly and blooms in the summer with lots of pretty, ruffled flowers on thin, wiry stems. It is not native to the UK, but it was brought there from the Mediterranean thousands of years ago, so it is now considered “naturalized.”
It used to be common in farm fields. In fact, its common name comes from the fact that it was once thought to be a weed of cornfields, along with corn poppy, corn marigold, and corncockle. Pesticides have made it hard to find in the wild, but because pollinators like it so much, it’s sold in wildflower mixes for wildlife gardens. Cornflower blooms are edible, too, and the petals make lovely garnishes to salads and other dishes.
Cornflowers come in many named varieties with different shades of blue, as well as pink, maroon, and white flowers. The original species is known for its deep blue flowers. Cornflowers are upright in habit, with plant height ranging from 30cm up to 120cm. The taller varieties make good cut flowers and cornflowers are an easy-to-grow addition to a cutting garden patch. Cornflowers bloom for up to three months in the summer, and since they only grow once a year, their life cycle is complete in one growing season. Cornflower plants may self-sow their seeds to bloom the next year, but they are not invasive, and any seedlings that you don’t want can be easily pulled out.
Cornflowers are easy for children to grow, either on their own or mixed with other cornfield annuals. Plant the seeds directly into the ground, lightly till it, and wait about 10 weeks for them to flower.
With their fluffy, fringed blooms in shades of vivid blue, pink, white and more, it’s easy to see why cornflowers are garden favorites. Getting these cheery annuals started at the right time is key to having them flower their best. So when should you plant cornflower seeds? Read on for tips on the ideal timing and techniques for growing these cottage garden classics from seed.
An Overview of Cornflowers
Before delving into timing, let’s start with some cornflower basics. Cornflowers (Centaurea cyanus) are upright annuals that grow 1-3 feet tall on slender stems lined with long, sword-shaped leaves. The flowers feature colorful ray florets surrounding a tufted center cone. They bloom from early summer through first frost.
Native to Europe, cornflowers have been grown in gardens for centuries. The traditional blue variety remains most popular, but flower breeders have introduced many more colors like rose pink, ruby red, and cream. Dwarf and double-flowered types are also available.
In addition to color, cornflowers offer easy care, a long bloom period, and excellent cutting and drying qualities They attract bees, butterflies, and other pollinators too No wonder they’ve earned a place in many gardens!
When to Sow Cornflower Seeds
As quick-growing annuals, cornflowers are almost always started from seed sown right in the garden Here’s an overview of the best timeframes
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Spring The most common planting window is spring, once temperatures have thoroughly warmed and the soil can be worked This gives cornflowers time to become established before their summer blooming period
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Fall: In mild winter climates (zones 7-10), cornflowers can be fall-sown to flower the following spring and summer. Protect young plants with a winter mulch.
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Successive Sowings: Make small, successive sowings every 2-3 weeks from early spring through midsummer. This extends the bloom season into autumn.
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Indoors: Start seeds indoors 6-8 weeks before the last expected frost. Harden off and transplant seedlings outdoors after frosts pass. This gives a small head start on bloom time.
The ideal planting date ranges from March through May for most regions. Sowing too early while soil is still cold and wet leads to rot and poor germination. Waiting until summer heat arrives stresses small plants.
Pay attention to your local last frost date and soil temperatures to zero in on prime spring planting time. Cornflowers need consistently warm soil of at least 50°F to sprout readily.
How to Plant Cornflower Seeds Outdoors
One of the simplest flowers to grow from seed, cornflowers thrive when direct sown right in the garden. Here are some tips for success:
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Choose a site with full sun and well-drained soil. Avoid enriching the soil, as cornflowers prefer poor conditions.
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Work the soil shallowly to create a smooth seedbed. Rake to remove debris.
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Sow seeds 1/4″ deep and 6-12″ apart in rows or groups. Cornflowers have a long taproot and don’t transplant well after sprouting.
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Water gently and keep the soil moist but not saturated for about 7-10 days until seedlings emerge.
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Thin to 12″ apart when the seedlings are 2-3″ tall. Discard the weaker ones.
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Water during droughts, but otherwise cornflowers are quite drought tolerant once established.
With proper sowing depth, moisture, and thinning, your cornflowers should thrive with minimal fuss. Before you know it, those delicate blue, pink, or white blossoms will be lighting up your garden!
Growing Cornflowers in Pots
Would you like to enjoy cornflowers on a patio or balcony? Container growing works perfectly. Follow these tips:
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Choose containers at least 12” wide and deep. This gives cornflower roots ample room.
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Use a high-quality potting mix, not garden soil. Mixed with perlite or another drainage aid, potting mixes prevent waterlogging.
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Sow 2-3 seeds per pot, 1/4” deep. Thin to leave the strongest seedling.
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Place containers in full sun. Rotate occasionally for even growth.
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Let the soil dry somewhat between waterings, but don’t let pots completely dry out.
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To prevent toppling, provide support with small trellises or tomato cages.
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For continuous color, make new sowings every few weeks. Older pots can be replaced with fresher plants.
With proper care, cornflowers will flourish wonderfully in containers to adorn decks, patios, and other outdoor living spaces.
Caring for Cornflowers Through the Season
Once your cornflowers get growing, a little attention goes a long way:
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Water regularly during the first few weeks after sprouting to establish a deep root system. Then water only as needed during droughts.
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Weed carefully around cornflowers when plants are small. Add an organic mulch later to smother weeds.
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Pinch or snip off dead blooms to encourage new buds. Allow some flowers to fade and go to seed for reseeding.
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Stake taller varieties if they begin falling over. Give plants ample space and good airflow to prevent disease.
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Pull up cornflowers after frost and add spent plants to the compost pile. Or, allow self-sown seeds to sprout next spring.
With proper timing, planting, and care, cornflowers are sure to brighten up your garden with their lively colors and carefree charm. Time those spring sowings right, and you’ll be rewarded with gorgeous blooms all season long. Soon these annual cottage garden classics will self-sow to become beloved returning guests each new year.
How to care for cornflowers
Remove faded flower heads to encourage more blooms to form. You can pull the plants up and compost them after they bloom, or you can let them self-seed and feed birds like goldfinches.
How to plant cornflowers
Ideally, sow seeds directly where plants are to flower. Otherwise sow in seed trays and harden them off before planting out in spring, spaced 15cm apart.
How to Plant and Grow Cornflowers from Seed
When should I plant cornflower seeds?
To grow cornflowers from seed (Bachelor Button), follow these steps: Sow seeds in early spring when the soil temperature reaches at least 50°F (10°C). If starting indoors, plant seeds 4-6 weeks before the last expected frost date. Planting depth and spacing: Sow seeds about 1/8-inch deep and 12 inches apart to give the plants enough room to grow.
When do cornflowers Bloom?
The ideal window is early spring once temperatures average 60 degrees F or above. This gives cornflowers time to establish before heat arrives. Q. How long do cornflowers bloom? Each stem blooms for 1-2 weeks. However, the blooming period lasts 4-6 weeks per plant in peak season. Extend flowering by promptly deadheading spent blooms.
How do you plant cornflower seeds?
Scatter the cornflower seeds evenly in the furrows, aiming for a spacing of 6 to 12 inches (15 to 30 cm) between plants. Cover the seeds with a thin layer of soil, approximately ¼ to ½ inch (0.6 to 1.3 cm) deep, and gently firm the soil. Water the area thoroughly after planting to ensure good seed-to-soil contact and promote germination.
How to grow cornflower seeds?
To grow cornflower seeds, prepare the soil first. Amend it with compost or aged manure to improve its fertility and drainage. Ensure the soil has a pH of 6.0 to 7.0 for optimal growth. Create a well-drained garden bed: Loosen the soil to a depth of at least 12 inches to promote healthy root growth. Planting: Sow cornflower seeds 1/4 inch deep and 1 inch apart in rows 12 to 18 inches apart. Cover the seeds with fine soil and water gently.
