Below is a guide for growing chrysanthemums in Australia. If you live in other parts of the world you will have to adjust the dates to suit your seasons and climate.
Best Planting Times: The large flowered types should be planted as soon as the weather and soil conditions permit. Small flowered types can be planted as late as December.
Soil Preparation: Chrysanthemums will grow in almost any soil type. But, the addition of humis material such as manure, compost, leaf mould, or peat moss is very beneficial. Superphosphate at the rate of 3 lbs. Per 100 square feet is recommended. Gypsum or Dolomite lime is also recommended at a rate of 10 lbs. Per 100 square feet.
Planting: Shallow planting, no deeper than the plant was in its rooting mixture. Initial planting should be in small pots until established and growing well. Space 15 inches apart in all directions. Good drainage is most important.
Cutting Back: If you have started your plants early and they are more than 15Ē tall on December 1st, we recommend cutting back to 4Ē or 6Ē, leaving some good green foliage or growth below the cut. The results will be better plants and better foliage at bloom time. On large flowered cultivars, select the most vigorous growth that results after the cut and make no further stops or pinches.
Pinching: When growth resumes after cutting back, removal of the very tip growing portion of the stem will promote more branching and flowers, and in some cases help determine bloom date. Large flowered types should not be pinched after 15th December. Small flowered types can be pinched up to 20th December. An earlier pinch date will be necessary for April blooming types. A second stop on 15th January is also recommended.
Lateral Removal: Large flowered types will only achieve their full potential of size and form if growth is restricted to several stems, three being an average. All sides laterals or branches must be removed as they occur. Remove the when they are short and soft so they do not rob the stem and developing buds of potential growth.
Disbudding: Large flowered types will only reach their maximum size if flower buds are restricted one to a stem. Remove all but the largest centre bud in a terminal bud cluster. Do this when bud clusters are still very small for best results. Terminal bud clusters will contain from 3 to as many as 5 buds. Crown buds which are the first to occur and are born singly, produce the earliest blooms.
Fertilisers: The regular use of high Nitrogen and Potassium fertiliser will greatly increase flower size and numbers. We recommend incorporating a slow release fertiliser such as Osmocote 14-14-14 at planting time plus a weekly feeding of a high analysis liquid such a Zest, after February 1st and until flower buds show colour. Change to a 0-10-10 fertiliser, or no fertiliser, after this date.
Insects and Disease: Careful observation and monitoring of your insect population is important. Donít let development spread from a few plants to a general infestation. Spot treatment of individual plants, particularly in the case of aphids, can often prevent spread to your whole planting. Lack of thoroughness in treating the underside of leaves is usually the reason for rapid reinfestation. Donít use the same insecticide more than three successive times or insects may become resistant. Soap and light oil sprays are quite effective, but the target insect or mite must be contacted to be effective. Donít use soap spays on blooms.
Winter Care: Chrysanthemums on the whole are not entirely winter hardy in areas of hard freeze. In cold winter areas, dig up plants, prune back, and store in a protective area such as a cold frame, or in any area where they can be protected from freezing. If left in the ground, mulch heavily with straw, decomposed manure or similar materials. In warmer areas, donít be hasty to cut back old stems until signs of new growth begin at base of plant.