Horticulture Magazine

‘Cornflower’ Centaurea Cyanus Plant Care & Growing Tips

beautiful blue cornflower in focus

Cornflower Overview

Official Plant NameCentaurea Cyanus
Common Name(s)Cornflower, Bachelor’s Buttons
Plant TypeAnnual
Native AreaEurope
Hardiness RatingH6
ToxicityEdible
FoliageOvate, long, spiky leaves
FlowersCommonly blue
When To SowMarch, April
Plant OutMay
Flowering MonthsJune, July, August, September
Deadheading MonthsJune, July, August
Sunlight

Preferred
Mostly Full Sun

Exposure
Exposed or Sheltered

Size

Height
0.5 – 1M

Spread
0.1 – 0.5M

Bloom Time
May – September

Soil

Preferred
Most soil types

Moisture
Well-drained or moist but well-drained

pH
Any

Cornflowers are beautiful additions to your garden, and can be a great choice for a meadow planting scheme or even placed in your vegetable garden.

When most people talk about cornflowers, they are talking about annual cornflowers, Centaurea cyanus. And it is these annuals that we are talking about in this article.

However, it is worth noting that there is also a perennial cornflower: Centaurea montana, and a range of other perennial Centaurea (knapweeds) which can be either herbaceous perennials or subshrubs – and these can also be great choices for your garden.

What are Cornflowers?

crowded clumps of Centaurea cyanus in a garden border
The annual cornflower, Centaurea cyanus, is a well-known meadow plant.

Another common name for this plant is ‘Bachelor’s Buttons’. 

It is a wildflower native to the UK which is very popular in cutting gardens and wildlife-friendly gardens. This is a hardy annual, with an RHS hardiness rating of H6.

It grows up to around 75cm tall, and bears beautiful deep (usually blue) flowers in the late spring and summer months, from around June to August.

Once, cornflowers were common as a weed in cornfields – hence the name. However, changes in agricultural practices mean that it is now very rare to find it growing naturally on farms.

Cornflowers are typically blue, but cultivars are also available in a range of other colours, from blues that are almost black, to pinks, reds and whites.

Named Cornflower Varieties to Consider

cornflower 'black ball' growing in a field
Cornflower ‘Black Ball’

You can purchase typical cornflower wildflower mixes, or wild cornflower seeds. However, you can also consider opting for one of the named cultivars for different forms or different hues.

Some options to consider include:

  • Black Ball – deep red flowers
  • Blue Ball – blue flowers
  • Blue Boy – gentian blue flowers
  • Blue Diadem – blue flowers
  • Classic Magic – a range of shades from deep, dark purple to lilac, bi-colour and white
  • Classic Fantastic – a range of flower colours from deep blue through light lilac blue and white.
  • Classic Romantic – red shading through to pink and white flowers.
  • Double Blue – deep blue flowers
  • Midget Blue – dwarf Centaurea cyanus with blue flowers, perfect for the front of borders or containers.
  • Polka Dot – bright and vibrant flowers in pinks, purples and whites.
  • Snowman – bright white flowers
  • Trailing Blue Carpet – blue, purple centred flowers. This cultivar works very well in hanging baskets or containers. Technically this is not Centaurea cyanus but Centaurea cyanoides (Dwarf Syrian cornflower), though it is another related hardy annual to consider.

Why Grow Cornflowers?

a fresh salad in a bowl laid out on a table, with a cornflower topping

Cornflowers are not only an attractive annual flower. They are also extremely beneficial for attracting bees, butterflies and other useful insects to your garden.

This means that they can be helpful for organic gardeners.

Cornflowers are relatively easy to grow, and low maintenance. In the right location, they can often self-seed readily.

What is more, they can provide us with a yield as well as just look pretty. You can eat the young shoots of cornflower, and the flowers can be added to a salad.

The flowers also provide an edible blue dye which is sometimes used in confectionery. The flowers are also an ingredient in several popular tea blends, such as ‘Lady Grey’.

Where to Grow Cornflowers

Cornflowers work very well alongside poppies and other hardy annuals in an annual wildflower meadow planting scheme.

Other native annuals for such a scheme include corn chamomile, forget-me-nots, wild candytuft, wild pansy and yellow rattle (which helps suppress grass growth).

They can also be an excellent choice in more formal planting of annual flowers in a cutting garden. Try planting them alongside marigolds, calendula, cosmos and zinnias, for example.

Reds, yellows and golds really bring out the blue of these flowers.

But perhaps the very best way to place cornflowers in your garden is within your vegetable garden. Since they are so good at attracting pollinators and other beneficial insects, they make excellent companion plants for a number of common annual crops – perhaps placed in pots or containers close to the main beds, or in a border along the edge of the kitchen garden area.

They can also do well in a bed with Mediterranean herbs or other plants which like free-draining conditions.

Cornflowers will thrive in a site in full sun in a well-drained loam or sandy soil. They are unfussy when it comes to soil pH, even tolerating very alkaline conditions.

These flowers do not require nutritionally rich conditions and in fact, can do well even in low fertility conditions. In fact, they can sometimes flower better where there is less nitrogen available in the soil.

This means they can be placed in a sheltered or exposed location.

When to Sow Cornflowers

Cornflowers can be sown undercover in a greenhouse or indoors in March, and planted out in May. Or they can be direct sown where they are to grow in April or May.

Sowing the seed directly is most common and usually germination rates will be good as long as the temperatures are between 10 and 16°C.

In areas where the winter does not get too cold, you can also sow cornflowers in an unheated greenhouse or polytunnel in September, for earlier flowers and larger plants the following year.

How to Sow Cornflowers

Cornflower seeds should be sown around 1cm deep, and if direct sowing, you are usually aiming for spacing of around 30cm between plants.

Seeds can be placed in orderly drills, though it is more common to broadcast the seeds into weed-free, raked soil along with other meadow seeds for more naturalistic planting.

Rake again lightly after sowing, and water in. Then water occasionally if there is no rain until the seeds germinate.

Caring For Cornflowers

As mentioned above, these annual flowers require very little care.

They are a low maintenance plant and can be a good choice for new gardeners, or when gardening with kids.

Watering

Over the summer, cornflowers should not require much additional watering, if any at all.

They are pretty tolerant of dry conditions and can handle some drought. In fact, overwatering or too much rain can be more of a problem.

So make sure the soil or growing medium is draining freely.

Cutting

a bouquet of Centaurea cyanus in a blue vase on a table
As the flowers appear, you can harvest them and eat them if you wish.

Or use them to make an edible dye. You can also cut flowers to place in an arrangement inside your home. But be sure to leave some flowers for the bees and other insects who share your garden.

Cut off the flowers just above a node and they should send up new flowers to replace those you have taken.

You can enjoy the cornflowers you cut as fresh flowers, or you can dry them. One good thing about drying cornflowers is that their blooms retain their colour well when dried.

Deadheading

Even if you are not making use of the flowers, you should remove spent flower heads. Deadheading regularly through the late spring and early summer should mean that you get more flowers over the summer.

However, make sure that you stop deadheading as summer progresses, and let some of your plants go to seed.

Not only is there the chance for self-seeding or seed collection for next year, the seeds are also attractive to birds, and make a good food source for several species.

Remember, these are annual plants, which will need to be re-sown (or allowed to self-seed) each year. But they can be an excellent choice for many UK gardens.

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