Gadenin日本語Get the appThe shape of the season
A chrysanthemum spends spring and early summer building a frame of stems, midsummer to late summer thickening that frame, and autumn flowering on it. Almost every job has to happen in the first half of the year, because the plant will not add stems once bud initiation starts. The autumn work is mostly picking, watching and then tidying up.
Nothing here is tied to a date, and it should not be. Bud set is triggered by the lengthening nights, so the flowering end of the season looks after its own timing wherever you garden. The jobs you control are all read off the plant itself: the height of the shoots, the length of the side growth, and whether the frost has been.
| Stage | Main job | The judgement call |
|---|---|---|
| Early spring | Lift, divide, replant the outer growth | New shoots 2 to 3 in (5 to 8 cm) tall and soil workable |
| Mid spring | Plant out, mulch, start balanced feeding | Hard frost past, and the plant clearly rooting away |
| Early summer | First pinch, then second pinch | Pinch one at 6 to 8 in (15 to 20 cm), pinch two when shoots reach 6 in (15 cm) |
| Midsummer | Last pinch, then stop. Put supports in | Whether there is time for a third pinch, or not |
| Late summer | Stop nitrogen, switch to high potassium, keep water steady | Is the plant getting light at night that will delay flowering |
| Autumn | Flowering. Deadhead, cut for the vase, record dates | Whether to row cover the buds through an early frost |
| After the first hard frost | Cut the blackened top growth down and clear it away | Cut back only once the top growth is genuinely finished |
Spring: the work that decides the whole year
As soon as the new shoots are 2 to 3 in (5 to 8 cm) tall, decide whether each clump is due for division. Anything that has been in place two years is due; anything showing thin growth or a bare middle is overdue. Lift, discard the woody center, replant the young outer pieces at their original depth and 18 to 24 in (45 to 60 cm) apart, and water them in properly.
Once the plants are visibly making new leaves, mulch 2 in (5 cm) deep over damp soil, keeping it clear of the crowns, and start a balanced liquid feed every two weeks. Check the growing tips for aphids weekly from this point, because the soft spring growth is exactly what they colonise first and a fortnight of not looking is enough for them to take a whole plant.
This is also the moment to move a plant that flowered late or poorly last autumn. If your records show it sits near a light, the division you replant should go somewhere genuinely dark. Nothing you do later in the season substitutes for that.
If you want spare plants or insurance against a hard winter, take basal cuttings from the young shoots at the same time as you divide. Rooted in three weeks, they are the cheapest backup a chrysanthemum bed can have.
Early summer to midsummer: pinch, then stop
The pinching program runs through early summer and is finished by midsummer. Each pinch multiplies the number of stems and lowers the plant, and the stopping point matters more than the starting point, because shoots need six to eight weeks of growth to be mature enough to set buds when the nights lengthen.
- Pinch the growing tip at 6 to 8 in (15 to 20 cm) tall Take out the top inch (2.5 cm) with your fingers, above a pair of leaves. The plant must be established and growing first.
- Pinch again when the side shoots reach 6 in (15 cm) Two or three weeks later, and pinch every shoot rather than just the tallest, or the plant finishes the season lopsided.
- Take a third pinch only if midsummer is still weeks away Worth it on a vigorous, early planted clump. Skip it entirely on anything planted late, which needs all the growing time it has.
- Stop pinching at midsummer and put the supports in Three or four canes per clump with soft twine run around at 12 in (30 cm) and 24 in (60 cm). Doing it now takes two minutes; doing it after the plant splays never works properly.
- Keep the water steady and even Soak to 8 in (20 cm) once or twice a week rather than sprinkling. Repeated wilting through the bud forming weeks costs flowers that do not come back.
Late summer and autumn: bud set, flowering and the frost
From late summer the plant begins reading the length of the nights and switching its tips over to flower buds. Stop the nitrogen feed now, switch to a high potassium liquid every two weeks, and check the bed after dark for any light that could interrupt the dark period. A plant next to a lamp will make leaves instead of buds no matter what else you do for it.
Once the buds show color, stop feeding altogether and just keep the water even. Deadhead spent blooms back to the next side shoot to keep the display going, and cut freely for the vase, which does the plant no harm at all. If a sharp early frost is forecast while the buds are still opening, a sheet of row cover thrown over the plants overnight and taken off in the morning usually buys another two or three weeks of flowering.
Leave the top growth standing until the frost has genuinely blackened it. Cutting a chrysanthemum down while it still has green leaves removes reserves that would have gone into the crown for the winter. Once it is finished, cut the stems to 4 in (10 cm) and clear every scrap of the old foliage away rather than composting it, because leaf spot overwinters on that debris and starts next year's infection from it.
Finish the year by writing down, for each plant, the date its first flower opened, how it stood up, and how badly it was affected by anything. That record is what tells you next spring which clumps to divide, which to move and which corner of the garden actually flowers on time.