Gadenin日本語Get the appThe plant stops the moment it sets seed
Cornflower is an annual with one purpose, and once a reasonable number of its flowers have turned into ripe seed heads the whole plant slows down, yellows at the base and finishes. That is the entire mechanism behind the season, and everything you do to extend the flowering is a way of preventing it. A plant that is deadheaded thoroughly flowers for two months or more; the same plant left alone gives three or four weeks and is a brown skeleton by midsummer.
The timing is tighter than with most flowers because a cornflower head goes over quickly. The fringed blue flower is good for around five days, then the petals shrivel and the head closes into a hard scaly cone which swells and ripens seed over the following fortnight. If you go round the patch once a week you will already have missed a proportion of them. Every few days is the honest interval, and in hot weather closer to every second day.
You can tell at a glance which heads need to come off. An open flower is soft and fringed and sits proud on the stem. A finished one is closed, papery, and slightly fatter at the base. Once you can see pale bristly seed showing between the scales, that head has already sent the plant its signal, and taking it off then buys you much less than taking it off a week earlier.
| Head stage | Appearance | What to do |
|---|---|---|
| Bud | Hard green scaly cone, tight | Leave, or cut the stem for the vase at the point of color showing |
| Open flower, days one to five | Fringed petals fully out, soft | Cut for the vase now if you want it |
| Just gone over | Petals shriveled and brown, head closing | Deadhead, this is the moment that matters |
| Swelling seed head | Closed, papery, fattening at the base | Deadhead, but the plant has already begun slowing |
| Ripe seed head | Splitting, bristly seed visible | Leave a few for self-seeding, remove the rest |
Cut deep, not just under the flower
The mistake that turns deadheading into a chore is snipping the spent head off immediately below the flower. That leaves a bare stalk that dies back, and it takes the plant a long time to produce a new flowering shoot from far up a woody stem. Instead, follow the stem down to the first pair of healthy leaves or the first side shoot and cut there. You are taking six to twelve inches (15 to 30 cm) of stem, and the plant responds by pushing new shoots from that point within a week or so.
This is the same cut you make when you are cutting flowers for the house, which is why a cornflower patch that is picked hard flowers better than one that is admired. Cut for the vase in the cool of early morning, choose stems where the flower has just opened, and put them straight into water. In the vase they last five to seven days, and buds that have started to show color will open indoors.
Toward the end of the season you can go further. When the whole plant is looking tired and the flowers are getting smaller, cut it back by roughly a third to a half, water it once and leave it. On an autumn-sown plant with a deep root that often produces a genuine second flush a few weeks later, running into late summer. On a small spring-sown plant it is a gamble, and half the time the plant simply stops.
- Go round every two to four days Take a small bucket or a trug and work along the row. Every few days is what maintains flowering; a weekly round lets too many heads reach the seed stage.
- Cut back to a leaf pair or a side shoot, not under the flower Follow the stem down six to twelve inches (15 to 30 cm) to the first healthy leaf pair and cut just above it. New flowering shoots come from there rather than from a bare stub.
- Cut for the vase in early morning, at the just-open stage Take stems as long as the plant allows and get them into water immediately. Picking hard is deadheading with a reward attached, and the plant is better for it.
- Shear the whole plant back by a third when it tires Water it once afterwards. On a strong, autumn-sown plant this reliably brings a second flush; on a weak one it may end the season, so try it on part of the stand first.
- Leave a few heads to ripen at the very end Once you are ready for the season to finish, stop deadheading and let a handful of heads ripen. That is your seed for next year and the source of next season's volunteers.
Do not deadhead and shear at the same time as an application of high-nitrogen feed in an attempt to force more flowers. The regrowth comes soft, flops immediately and mildews. Cutting back plus a single deep watering is the whole treatment.
Why plants stop flowering early
If a stand goes over well before midsummer, the cause is almost always one of four things and none of them is bad luck. Heat is the first: cornflower is a cool-season flowerer and sustained temperatures above 85F (29C) shut it down regardless of how well it is deadheaded, which is why gardeners in hot climates get their season in spring and treat summer as the end. Shade is the second; anything less than six hours of direct sun gives fewer, smaller flowers on weaker stems.
The third is crowding, which traces back to thinning. Plants left at two or three inches (5 to 8 cm) apart make one stem each, flower once at the top of it, and have nothing left to give. The fourth is collapse. Stems that have gone flat in a storm keep flowering for a while but the plant puts its energy into re-orienting rather than branching, and the season shortens noticeably. Support and spacing are, in that sense, part of the flowering question rather than separate from it.
| Symptom | Likely cause | Fix |
|---|---|---|
| Whole stand over by early summer | Sustained heat above 85F (29C) | Nothing this year; sow in autumn next time to get an earlier start |
| Few flowers, long weak stems | Too little sun or too much nitrogen | Move the patch to full sun, stop feeding |
| One flower per plant then finished | Not thinned, plants too close | Thin to nine to twelve inches (23 to 30 cm) next time |
| Flowering slowed within three weeks | Deadheading missed, seed set | Cut back hard by a third and water once |
| Flowers getting smaller each week | Plant exhausted or drought stressed | Deep soak, shear back, expect a smaller second flush |
Petals for the kitchen, and drying them
Cornflower petals are edible, mild and slightly sweet with very little flavor of their own, and their whole point is color. Pull the fringed florets out of a freshly opened head and scatter them over salads, soft cheese, iced cakes or drinks. Take flowers that have just opened, in the morning, from plants you have not sprayed, and use the florets rather than the whole head, since the base of the head is fibrous and bitter.
The reason cornflower turns up in so many tea blends is that the blue survives drying, which almost no other blue flower manages. Pick heads on a dry morning at the just-opened stage, pull the florets free, and spread them in a single layer on paper or a mesh rack somewhere warm, dark and airy. Dark matters: light bleaches the color as it dries. They are done in three or four days when they crumble rather than bend. Stored in a closed jar away from light they hold their blue for a year or more.
Whole dried heads are worth doing too, hung upside down in small bunches in the same dark, airy place, and they keep both the color and the fringed shape for winter arrangements. Anything you pick for eating or drying is a head you have deadheaded, so this costs the flowering season nothing at all.