Gadenin日本語Get the appWhy the clump has to be split every year or two
A chrysanthemum spreads outwards from underground stolons that push new shoots up around the edge of the clump each spring. The original center does not renew itself. It becomes woody, its roots die back, and the shoots it produces get thinner and shorter every year. Left alone, a clump that flowered beautifully in its first autumn becomes a ring of weak growth around a dead middle by its third.
Splitting is therefore maintenance, not multiplication. The plant is not declining because of your soil or your feeding, and no amount of either will reverse it. Lifting and replanting the young outer growth every one or two years is what keeps a chrysanthemum permanently in a garden, and it is why a well kept plant can outlive the person who bought it.
Dividing also breaks the cycle of soil borne trouble. Eelworm, leaf spot and various rots all build up around an undisturbed old crown, and replanting fresh young pieces, ideally shifted a few feet along the bed, resets that. If a clump has been visibly diseased, replant the divisions somewhere else entirely rather than back into the same hole.
Dividing in spring, step by step
Divide in spring, once the new shoots at the base are 2 to 3 in (5 to 8 cm) tall and the soil is workable. At that stage you can see exactly which growth is alive and where to cut, and the divisions have the whole season ahead of them to root before winter. Autumn division, immediately after flowering, works in mild areas but gives a much smaller margin.
Work on a dull day or in the evening if you can, and never let the roots dry out while you are handling them. Have the new planting positions dug and a bucket of water ready before you lift anything.
- Lift the whole clump with a fork Push the fork in a good 8 in (20 cm) out from the shoots on all sides and lever the clump up whole. Getting the roots up intact makes every later step easier.
- Wash or shake enough soil off to see the crown You are looking for the boundary between the hard, dark, woody old center and the pale, fleshy young growth around the outside. You cannot judge that through a ball of soil.
- Discard the woody center without hesitation The old center is spent. It looks substantial and it is the piece most people keep, and it will give the weakest plant of the whole batch.
- Break off outer pieces with shoots and their own roots Pull the outer growth apart by hand where you can. Each division wants one to three healthy shoots and a decent handful of white roots attached. Pieces smaller than that will grow, but flower late.
- Replant immediately at the original depth Crown level with the soil surface, 18 to 24 in (45 to 60 cm) apart, firmed in and watered heavily. Any division you cannot plant at once goes into a pot of compost, not onto the bench.
- Pinch the tips once they are growing again Wait for clear new leaf growth, which shows roots have taken, then start the normal early summer pinching program. A division is a young plant and needs it as much as any other.
One old clump usually yields four to eight good divisions. Plant what you need, give the rest away, and resist replanting all of them into the same bed just because you have them.
Basal cuttings, for more plants than division gives
The other route is basal cuttings, taken in early spring from the young shoots coming up around the base of the crown. This gives many more plants from one parent than division does, and the resulting plants are uniform and completely free of the old crown's problems. It is how nurseries produce their stock.
Cut shoots 2 to 3 in (5 to 8 cm) long cleanly at the base, strip the lower leaves, and push them into a gritty, free draining compost around the edge of a pot. Keep them somewhere bright but out of direct sun at about 60F (15C) and lightly humid. Roots form in two to three weeks. Pot up individually, grow on frost free, and plant out once hard frosts are past.
Cuttings are worth taking specifically for insurance in a cold area. A few rooted cuttings kept frost free under cover over winter means that if a hard winter or waterlogging kills the parent clump in the ground, you have not lost the plant.
| Method | When | Plants from one clump | Use it when |
|---|---|---|---|
| Division of outer growth | Spring, shoots 2 to 3 in (5 to 8 cm) tall | Four to eight | Routine maintenance of an established clump |
| Basal cuttings | Early spring, from young basal shoots | Twenty or more | You want many plants, or winter insurance |
| Autumn division | Straight after flowering | Four to eight | Mild winters and free draining soil only |
| Leaving the clump undisturbed | Not applicable | None | Never for more than two years running |
Keeping track of what you split
Write down which clump you divided, the date, how many divisions it gave and exactly where each one went. Divisions from one plant look identical for months, beds get rearranged every time you lift them, and by the following autumn nobody remembers which mound came from which parent.
Note the vigor of the parent as well. A clump that has produced weak divisions two years running is telling you something about that position or that soil, and the useful response is to plant its next divisions somewhere else rather than to keep feeding it.