Gadenin日本語Get the appThe shape of the year
Cornflower is an annual, but where winters are mild the useful version of the plant behaves like a biennial for a few months: sown in autumn, it makes a rosette, sits through winter, and flowers the following summer at roughly twice the size of a spring sowing. That single shift moves the busiest part of the year from spring to autumn, and it is the reason the calendar below starts where it does rather than in spring.
The whole cycle then divides into four unequal parts. Autumn is sowing and establishing. Winter is doing nothing except protecting the crown from wet. Spring is thinning, pinching and, crucially, getting the support in before the plants need it. Summer is a long stretch of deadheading every few days, ending in the decision about how much seed you let ripen. Everything difficult about the plant happens in a handful of narrow windows within that.
| Season | Main jobs | The mistake to avoid |
|---|---|---|
| Early to mid autumn | Sow direct in lean, sunny, well-drained ground; protect from slugs | Sowing too early, so plants go into winter large and soft |
| Late autumn to winter | Nothing. Keep the crowns from sitting wet; clear heavy leaf fall | Mulching over the rosettes, which rots the crowns |
| Early spring | Final thinning to nine to twelve inches (23 to 30 cm); weed | Leaving the plants crowded, which halves the stem count |
| Mid spring | Put in netting or twiggy support; pinch spring-sown plants | Waiting until the plants look like they need support |
| Late spring to midsummer | Deadhead and cut every two to four days; watch stem tips for blackfly | Skipping a week, which lets seed set and slows the plant |
| Late summer | Shear back by a third for a second flush; watch for mildew | Feeding to force regrowth, which produces soft, mildewed stems |
| End of season | Let a few heads ripen for seed; clear and dispose of mildewed plants | Composting badly mildewed material back onto the bed |
Autumn and winter: sow, then leave it alone
The autumn sowing wants roughly six weeks of growing weather before hard frost. That is enough to make a rosette a few inches across with a taproot already going down, which is the state that survives winter best. Sown much earlier and the plants get large and soft and rot at the crown in a wet winter; sown much later and they go into cold with two leaves and never build the root that gives you the extra size. Slugs are the main risk at this stage and worth checking for at night until the seedlings have four true leaves.
After that, winter is the easiest part of the growing year: do nothing. Do not feed, do not water, and above all do not mulch. A rosette buried under compost or a mat of fallen leaves sits wet at the crown and rots, which is the commonest way an autumn sowing is lost. Sweep or rake heavy leaf fall off the patch. In a garden with sharp frost but no deep freeze, a light covering of row cover over the worst nights is worth having, but ordinary cold is not the problem; sitting water is.
Where winters are too cold or too wet for this, the equivalent window is late winter under cover in deep cells, planting out as soon as the ground is workable, or the earliest possible direct sowing in spring. Accept the smaller plant and shift the rest of the calendar forward by a few weeks.
Spring: two jobs, both easy to leave too late
The first is thinning. Once growth restarts, take the stand out to nine to twelve inches (23 to 30 cm) between plants, going wider for an autumn sowing because those plants get so much bigger. Doing it now rather than in autumn means winter losses have already declared themselves and you end up with an even stand. This is dull work and it is the difference between plants that branch into a dozen stems and plants that make one each.
The second is support, and it has to happen while the plants still obviously do not need it, at around a foot (30 cm) tall. Horizontal netting on short stakes for a cutting row, twiggy branches pushed in among the plants for a border. Once cornflower has gone over in a storm you cannot put it back, so the whole technique is to be early. Pinch spring-sown and container plants at the same time, when they have four or five leaf pairs, to get them branching from lower down.
The other spring job is deciding what to do with volunteers. Cornflower seeds itself readily into bare ground, and seedlings that came up in autumn and overwintered are as good as anything you sowed deliberately and worth keeping. Spring-germinated volunteers are weaker and usually not worth the space. Thin the ones you keep to the same spacing as the sown stand rather than leaving them in clumps.
- Thin to final spacing as growth restarts Nine to twelve inches (23 to 30 cm) apart, wider for autumn-sown plants. Pull in damp soil so the roots come away without disturbing the neighbors.
- Put the support in at about a foot (30 cm) of growth Netting on short stakes set at roughly 12 inches (30 cm), or twiggy prunings pushed in among the plants. The plants grow up through it and hide it entirely.
- Pinch the tips of spring-sown and container plants At four or five leaf pairs, nip out the top inch (2.5 cm). It delays the first flower by about ten days and roughly doubles the stem count.
- Sort out the volunteers Keep autumn-germinated self-sown seedlings and thin them properly. Hoe off spring-germinated ones unless you have room, since they flower late and briefly.
- Weed thoroughly while you can still see the ground Once the stand closes over you cannot get in without breaking stems. Get the bed clean before the plants meet across the rows.
Summer: deadhead, then decide about seed
From the first flower onward, the schedule is simply every two to four days, all summer. Cut spent heads back to a leaf pair or side shoot six to twelve inches (15 to 30 cm) down rather than snipping under the flower, and take cut flowers for the house at the same time, since picking hard and deadheading are the same operation. Check the stem tips for blackfly on the same rounds. When the plants tire and the flowers get smaller, shear the stand back by a third, water it once, and expect a second flush on strong autumn-sown plants.
The end of the season is a deliberate choice rather than an event. Stop deadheading and cornflower sets seed and finishes within a few weeks, and the seed it sheds germinates freely in any bare ground nearby. In a cutting patch or a tidy border, let a handful of heads ripen for next year's sowing and clear the rest before they shed. In an informal or wildflower planting, let the whole stand go and you have a self-perpetuating colony, though the plants come up where they choose rather than where you want them and the stand drifts across the bed year on year.
Either way, keep the seed heads dry. Cut ripening heads on a dry morning once the bracts split, finish drying them indoors in a paper bag, and rub the seed out. It stays viable for several years in a cool dry place.
Do not let a mildewed stand ripen its seed and shed it where it stood. Pull those plants and dispose of them rather than composting, and take your seed from a clean part of the patch instead.
The four dates worth writing down
Keep a note of the sowing date, the date the first seedlings appeared, the date the first flower opened, and the date you put the support in along with whether the plants stayed upright. Those four are enough to calibrate the entire calendar for your own garden, because every important cornflower decision is a timing decision and none of them is the same in two different places.
Add the first-appearance dates for mildew and blackfly and the position of each stand. Cornflower seeds itself, so knowing where you deliberately sowed as against where volunteers came up tells you which corner of the garden the plant actually prefers, which is usually the leanest and sunniest one.