Chrysanthemums bloom naturally from mid-August to mid-January and are divided into those that flower mid-August to mid-September (earlies), before the frosts and can therefore be grown in the garden, and those that flower mid-October onwards (lates), which are normally grown in pots so that they can be more easily brought in and flowered in a greenhouse. Those that flower in between these dates are called mid-season.
EARLY FLOWERING CHRYSANTHEMUMS bloom outdoors in August and September in the open ground and can be planted out in the garden from April. Before planting apply our Chrysanthemum plant food or another good general fertiliser and rake it in. Plant firmly about 60cm/2in apart. You can plant closer if you want blooms for cutting or further apart if you need to fill a large area. Insert a cane, tie the stem to it and water in. Feed every two to three weeks until August when the buds will be starting to form. If you give too much feed you get a larger but softer plant, which can be more susceptible to disease.
Most cultivars can be stopped about the 1st week May, or, if it is after this date, when they are about 15cm/6in tall. If they have formed premature buds it is best to cut them back hard, at least half their height. This will encourage new shoots to grow from lower down without buds. Four or five of the resulting side shoots should be retained. For blooms, one bud should be allowed to develop on the top of each side shoot with other buds being removed as they appear. For sprays all buds should be allowed to develop.
LATE FLOWERING CHRYSANTHEMUMS are grown in pots outside until frost is likely, then are moved into the greenhouse to flower, flowering in November and December. On arrival they can be treated the same as garden ones, but in early May they should be put into 13cm/5in pots and in early June they should be potted into their final pots, a 20cm/8in or 23cm/9in using a cane suitable for the final height of the variety. They can then be stood outside. If you are not sure whether they are ready to pot on, turn the pot upside down and tap the plant out, making sure to stop it falling. If the root covers the outside of the soil then it is ready. If not put it back in the existing pot and leave it for another week. About the beginning of June the top 2.5cm/1in of the stem should be removed, this is called pinching or stopping.
Four side shoots should be retained with only one bud at the top of each stem being allowed to develop if you want blooms. For sprays you simply let all the buds develop. The plants should be fed every two to three weeks until early September when the buds start to form. When buds start to show colour about the end of September move them back into the frost-free greenhouse. Give plenty of ventilation to keep the humidity down and prevent damping of the petals.