Euphorbia pulcherrimum

Poinsettia, Euphorbia pulcherrimum, has become as much as part of the traditional Christmas as holly and ivy, bearing colourful bracts in a deep shade of festive red. It's native to Mexico where it can grow quite large, but it tends to remain small when grown here as a houseplant. Poinsettias are often thrown away at the end of the Christmas season, but with a little care you can keep them throughout the year, and the bracts will redden up again the following Christmas.

For best results grow poinsettia in bright light, away from strong sunlight and draughts. Water sparingly and mist regularly. Feed monthly with a low nitrogen, high potassium fertiliser.

To encourage the bracts to redden up the following Christmas, hard prune in April, to about 10cm. Repot into fresh compost, and keep in a cool place over summer, such as a north-facing window sill. From November onwards, place your poinsettia in a dark room for 12 hours each day, to mimic the short day lengths that stimulate flowering. Poinsettias need a constant temperature of around 18°C to develop a good red colour, so make sure they don't get cold.