Cotton is a tropical plant which can be grown indoors or in a greenhouse in the UK.
Cotton plants grow to a height of about 1.5 metres. In very mild areas, where warm summers are predicted, it is worth trying to grow the plant outdoors. Here it should be treated as a half-hardy annual and can tolerate minimum temperatures 19°C/65°F.
Sow the seeds, two or three at a time in a 9 cm pot in late March to April at a temperature of 15-20°C. As they germinate, remove the weaker seedlings to leave one healthy plant per pot.
As the plants grow, transfer to larger pots and keep slightly damp at all times. As soon as they have four pairs of true leaves feed weekly with a high potash liquid fertilizer or tomato feed.
If they are going to be grown outside, harden the young plants off by placing outside in their pots in the spring. Plant them out when all danger of frost is past. A rich fertile soil, with high levels of organic matter, is best for cotton. Try some on a sheltered patio in full sun, or in a border close to a south facing wall. The plants will need some support as they blow over easily. Keep well watered.
If growing indoors, select a potting compost which contains loam rather than a peat-based one, and use at least a 30 cm diameter pot.
Petals from the attractive silky flowers can be eaten: they taste a little bit like okra. If left uneaten they should develop into the fluffy seedpods, or bolls, by late August.
If plants are being grown outdoors and the weather is wet, the bolls may need picking else they may rot. Shake them dry several times and put on a sunny window sill and turn daily, until they open.
Red spider mite can be a problem, especially on plants grown in greenhouses or under glass. This can be treated with an insecticidal soap spray, or by frequent misting the plants with water.