Amazing annuals: Cornflowers
Easy to grow and essential for cottage gardens.
Along with poppies and corn marigolds, cornflowers (Centaurea cyanus) completes the trio of wild flowers associated with fields of wheat. They are popular as ‘wild flowers’ for meadows though, like most annuals they need disturbed soil and will not perpetuate themselves in permanent grassland (meadows). Traditionally bright blue, the range of colours now includes pinks, mauve, white and deep maroon. Heights also vary enormously from the wild 90cm or so to very compact. There is a very low, spreading form that looks as though it has been selected by the local cat as a sofa. I thought it was an abomination until I noticed it was C. cyanoides and actually a wildling rather than a plant-breeders attempt to make a lovely flower hideous. In my self-diagnosed tendency to be awkward I will forgive it since it is a natural habit but I still don’t want it in my hanging baskets.
One reason for this is that cornflowers, like many hardy annuals, have a relatively short period of beauty. And cornflowers, lovely though they are, always have a mix of unopened buds and dead flowers among their perfect blooms. For this reason I don’t think they make great cut flowers, despite what everyone says. It is because I am mean and hate to cut lots of unopened buds along with the flowers and unless you cut individual flowers with 10cm stems you do waste a lot of plant.
Cornflowers are tall, willowy, elegant plants. They can be sown where they are to bloom in spring, from March to May, or they can be sown in autumn. Autumn sowing is always best for hardy annuals because it allows the plants to make large root systems, in preparation for flowering. Spring sown, the plants rush to flowering no matter how well established the plants and that can mean premature flowers, and fewer of them. After all, the plants just want to flower and set seed. So we should deadhead, but life really is too short to deadhead cornflowers.
I like to sow lots of annuals in spring in cells trays, partly because my soil is not easy to work into a fine tilth at present. But be aware that you have to watch the seedlings carefully and plant them out as soon as they have filled the cell with roots. Thin to no more than three per cell as soon as they germinate – too much competition will force them to bloom prematurely. And plant before they get starved, cramped or in any way stressed or, again, they will run to flower before they have made a decent size.
When sowing in-situ the same principle applies. As soon as the seedlings are about 10cm high they need to be thinned. Water before you start to prevent later wilting, then thin the plants to about 10cm apart. Depending on how thinly you sowed this can involve an awful lot of wasted seedlings. You can remove some carefully and transplant them to fill gaps but not all hardy annuals respond well to this sort of treatment. As soon as you have thinned the seedlings water them well to settle them in.
When it comes to varieties I must say that I like the ‘Classic’ series which all have bicoloured flowers in a range of colours. ‘Classic Fantastic’ is blue and white, ‘Classic Romatic, pink and white and ‘Classic Magic’ purple (burgundy to black) and white. All are a respectable 80cm high.
Reassuringly, Robinson wrote: ‘The young plants stand our hardest winters, and flower better grown thus than if sown in spring.’
The Biking Gardener 
Ours may have started out in early winter as well, but I do not know. I never watched for them. I only know that they were ready to bloom in spring. I do not think they would have bloomed as early as they did if they did not start during winter, even if they primarily dispersed roots, without much growth on top. When I was a kid, I thought that they were only blue. I had never seen varieties with any other color.
This is a good series of posts, both enjoyable to read and informative.
Thank you – takes my mind off the flooded garden too!