Chrysanthemum

Growing tips

Site and soil preferences
Plant the rooted cuttings or new divisions of border plants in spring as soon as the soil begins to warm up. They like average, free-draining soil in full sun. Cuttings raised in a greenhouse shouldn't be planted outside until the danger of frost has passed. Keeping plants healthy
Plants develop into a healthy clump, known as a stool, which is easy to divide into smaller divisions, each with a single shoot and some roots. If you lift and divide your plants every third year, they'll retain their vigour and produce stocky stems that are easier to support. If you fail to lift and divide them, don't worry: the plants will survive but will gradually lose vigour.

Propagation
As well as dividing plants, you can take basal cuttings in spring when you lift the plants and store them in trays of moist compost; they'll soon produce young shoots. Cut them off close to the base of the plant and root them in moist perlite, or a mix of sand and compost, kept in a warm place.
Take cuttings from the parent plant in mid-winter and place them in moist perlite. Cuttings should produce roots by March and be ready for planting outdoors in May. Pinch back (see below) spray varieties as soon as the cuttings have rooted to promote bushy growth. Then feed and water well. Outdoor varieties should be happy with less attention, provided they're grown in reasonably fertile soil.

Disbudding
The group called 'disbudding chrysanthemums' (e.g. 'Regalia' and 'Dorridge Beauty') perform better if the side buds are nipped off to leave a single, larger flower. Without disbudding, they often produce congested stems of flowers that are inclined to be top heavy.Pinching back
Also known as stopping, you should pinch back the larger-flowered kinds by removing the top bud of the single stem. This results in new side shoots; select the two strongest and remove the rest. Once they've lengthened, pinch out their tips to encourage two more stems to form. Consequently, a single cutting will produce four blooms. If you want more flowers, which will be smaller, leave three new shoots instead of two after each pinching.

Staking
Most chrysanthemums, particularly the taller kinds, need support. Use metal linking stakes (available from garden centres) or canes and pea sticks with string. If you plan to grow your chrysanthemums in large drifts, try fixing a horizontal layer of wide-mesh bean netting above the plants at a height of around 45cm (18in). It may initially look unattractive but provides good support once the plants have grown through the netting, which makes it worth the wait.

Problem solver
Avoid over-feeding, especially the spray varieties, because the taller, lanky plants become very floppy and the lush growth also invites disease.
Control fungal diseases, such as powdery mildew, with specific fungicides. Plants forming warty patches on their undersides are suffering from white rust and should be destroyed. Eelworm produces browning leaves but can be cured by heat-treating the plants. Dig up the plants, wash off the soil and immerse the roots in water at a temperature of 46°C (115°F) for five minutes.
Indoor and greenhouse varieties are more prone to pests and diseases; regularly check each plant carefully. Remove any aphids promptly as they can introduce viruses.

(http://www.bbc.co.uk/gardening/plants/plantprofile_chrysanthemum.shtml#growing_tips)