Cornflower (Centaurea cyanus) is an easily grown hardy annual wildflower that is quick to grow and blooms in summer, bearing masses of pretty, ruffled flowers on slender wiry stems. While not native to the UK, it was introduced from the Mediterranean thousands of years ago and is considered ‘naturalised’. It used to be a common sight in arable fields along with corn poppy, corn marigold and corncockle. As a result of pesticide use, it’s now rarely seen in the wild. But due to its popularity with pollinators, it’s sold in wildflower mixes for wildlife gardens.
The original species is beloved for its deep cornflower blue blooms, but there’s now a wide choice of named varieties in different shades of blue, as well as pink, maroon, and white. 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, with their frilly vividly colored blooms are a beloved old-fashioned flower that no cottage garden would be complete without. Getting the timing right when planting these hardy annuals is key to having them flower their very best. So when is the ideal time to sow cornflower seeds?
In this article, we’ll go over the basics about growing cornflowers and provide tips on the best planting times for various climates. We’ll also give advice on sowing techniques, caring for cornflowers throughout the season, and how to keep them blooming gorgeously right up until frost.
Before diving into timing, let’s start with some background on cornflowers. Also called bachelor’s buttons, cornflowers (Centaurea cyanus) are upright annuals that grow 1-3 feet tall. Their stems are lined with long, sword-shaped leaves.
The flowers have a central tufted cone surrounded by colorful ray florets in shades of rich blue pink burgundy, and white. They bloom from early summer through the first fall frost.
Native to Europe, cornflowers have graced cottage gardens for centuries. The classic blue variety remains most popular but there are now many more colors to choose from. There are also dwarf and double-flowered types available.
In addition to their diversity of hues, cornflowers offer easy care, a long bloom season, excellent cutting/drying qualities, and attract pollinators. With all they have going for them, it’s no wonder cornflowers are garden favorites!
Knowing the Best Time to Sow Cornflower Seeds
As quickly growing annuals, cornflowers are directly sown in the garden, rather than being started indoors and transplanted. Here are the optimal timeframes for planting:
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Spring – The most common planting time is spring, once the soil has thoroughly warmed and can be worked. This gives cornflowers time to establish before beginning their summer-long bloom period.
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Fall – In mild winter regions (zones 7-10), cornflowers can be planted in fall to flower the next spring/summer. Use a winter mulch to protect young plants.
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Successive Sowings – For extended bloom well into autumn, make small, successive sowings every 2-3 weeks from early spring through midsummer.
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Indoors – For a slight head start on blooms, seeds can be started indoors 6-8 weeks before your last expected frost date. Harden off and transplant the seedlings after danger of frost has passed.
For most areas, the ideal direct sowing time is from March through May. Planting too early while soil is still cold and wet leads to rot and poor germination. Waiting until summer when hot weather arrives stresses small plants.
Pay close attention to your local last frost date and soil temperatures. Cornflowers need consistently warm soil of around 50°F to sprout well.
Easy Techniques for Planting Cornflowers from Seed
One of the simplest flowers to grow from seed, cornflowers thrive when directly sown into the garden. Here are some tips for success:
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Select a site with full sun exposure and well-drained soil. Avoid enriching the soil, as cornflowers prefer less fertile conditions.
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Lightly work the top few inches of soil to create a smooth seedbed. Rake away any debris.
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Sow seeds 1/4″ deep and 6-12″ apart in rows or groups. Cornflowers have a long taproot and dislike being transplanted once sprouted.
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Gently water and keep the soil evenly moist for 7-10 days until seedlings emerge.
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When seedlings reach 2-3″ tall, thin them to 12″ apart. Discard the weaker ones.
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Once established, cornflowers are quite drought tolerant. Just water during extended dry spells.
With proper planting depth, moisture, spacing, and thinning, your cornflowers will thrive with minimal work required. Before you know it, those lovely blue, pink, or white blooms will be lighting up the garden!
Growing Cornflowers Successfully in Containers
You can also enjoy cornflowers on a patio or balcony by growing them in containers. Here’s how to do it right:
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Select containers at least 12″ wide and deep to give cornflower roots ample room.
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Use a high quality potting mix rather than garden soil. Mix in perlite or another drainage aid to prevent sogginess.
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Sow 2-3 seeds per pot, 1/4″ deep. Thin to leave just the strongest seedling.
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Place containers in full sun areas. Occasionally rotate for even growth.
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Let the soil dry somewhat between waterings, but don’t allow pots to completely dry out.
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Give tall varieties support with small trellises or cages to prevent toppling over.
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For continuous color, make new sowings every few weeks. Replace older pots with fresh plants.
With proper care, cornflowers will flourish wonderfully in containers to adorn outdoor living areas.
Simple Tips for Caring for Cornflowers All Season Long
Once your cornflowers are up and growing, just a bit of care will keep them healthy and blooming prolifically:
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Water regularly the first few weeks after sprouting to get plants established. After that, only water during droughts.
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Carefully weed around plants while they are small. Later on, apply an organic mulch to smother weeds.
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Pinch or snip off spent blooms to encourage new flower buds. Allow some fading blooms to go to seed for reseeding.
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Stake taller varieties if they start to fall over. Give all plants ample space and airflow to avoid diseases.
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After frost, pull up dried cornflowers and add to the compost pile. Or let self-sown seeds sprout next spring.
Follow these simple tips on timing, planting, and care and your cornflowers will surely brighten up your garden with their lively colors and easygoing charm. Allow some seeds to self-sow and these cheery annual cottage garden classics will return as beloved plants each new year.
Frequently Asked Questions About Growing Cornflowers
Below are answers to some common questions about successfully raising cornflowers:
How do you plant cornflower seeds?
Scatter the seeds evenly in furrows, aiming for 6-12 inches between plants. Cover with 1⁄4-1⁄2 inch of soil and gently firm it down. Water thoroughly after planting to promote germination.
When is the best time to plant cornflower seeds?
For summer blooms, sow seeds in early spring once soil temperatures reach at least 50°F. If starting indoors, plant seeds 4-6 weeks before your last expected frost.
How long do cornflowers bloom?
Each stem blooms 1-2 weeks. But the total bloom period per plant lasts 4-6 weeks at peak season. Promptly deadheading spent blooms extends overall flowering time.
How do you care for cornflowers?
Remove faded blooms to encourage more flowers. After bloom time, pull plants and add to compost or allow self-sown seeds to feed birds like goldfinches.
How do you grow cornflowers from seeds?
Prepare soil and create a well-drained bed. Sow seeds 1⁄4 inch deep and 12 inches apart. Cover with fine soil, water gently, and thin seedlings later on. Cornflowers are easy to grow from seed with basic care.
Bring Vibrant Cornflower Colors to Your Garden
With their fluffy, fringed blooms in vivid shades of blue, pink, burgundy, and more, it’s easy to see why cornflowers enchant gardeners. Follow the tips above on when and how to sow these hardy annuals, and you’ll be rewarded with gorgeous, carefree flowers all season long. The right planting time is key, but cornflowers are quite unfussy once established. Let some reseed so these beauties return each new year to charm your garden.
How to grow cornflowers[image id=”169685″ size=”landscape_thumbnail” title=”Cornflowers growing in a pot. Neil Hepworth” alt=”Cornflowers growing in a pot. Neil Hepworth” classes=””] Cornflowers growing in a pot. Neil Hepworth
Grow cornflower plants in sun and well-drained soil, sowing seed directly into weed-free ground or into pots, in spring. Thin out the resulting seedlings. After that, little care is needed apart from deadheading to encourage more blooms. Cornflowers are easy for children to grow, either on their own or mixed with other cornfield annuals. Sow seed directly onto the soil, lightly rake over and wait for them to flower within around 10 weeks.
How to plant cornflowers[image id=”169686″ size=”landscape_thumbnail” title=”Planting out cornflowers. Jason Ingram” alt=”Planting out cornflowers. Jason Ingram” classes=””] Planting out cornflowers. Jason Ingram
Ideally, sow cornflower seeds directly where plants are to flower from March to May, 0.5-1cm deep. Sow in drills, or you can simply scatter the seed and then rake lightly to cover with soil. Thin the resulting seedlings to 10-15cm apart. Making several sowings throughout spring will ensure a succession of flowers during the summer.
If ground or weather conditions do not permit outdoor sowing, you could sow cornflowers in pots in general-purpose, peat-free potting compost mixed with a third by volume of coarse grit. Place under cover in an unheated greenhouse or polythene tunnel and harden cornflower seedlings off before planting out in late spring, spaced 15cm apart. Shorter-growing varieties are best for pots as taller ones tend to flop without support. Cornflowers can also be sown in pots from August to October and planted out in autumn or grown on, overwintered in pots and planted out the following spring.