December is a peak month for giving and receiving houseplants. Bulbs and plants that have been treated to flower indoors in winter are grown in vast numbers for the Christmas trade. If you have a cool greenhouse you can prepare the plants for forcing yourself but garden nurseries are now very accomplished at this process. Prepared plants include forced bulbs such as Narcissi and Hyacinths, and outdoor plants such as Cyclamen, Primula and Cineraria. These can be displayed in a cool living room for Christmas and winter decoration, then returned to the garden in the spring.
The most popular Christmas houseplant is the red Poinsettia (Euphorbia pulcherrima). With its large bright red bracts it makes a bold statement in the house. Place it near a south facing window, where it will get plenty light. Water well until the bracts fall, then discard. They can be kept until next year but will need special treatment to be at their best.
Other popular plants include colourful Azalea indica and Solanum pseudocapsicum (winter cherry), both of which need extra humidity. So spray them frequently with tepid water (rain water if possible).
Christmas Cactus or Crab Cactus (Schlumbergera buckleyi) produces pink, white or carmine flowers in winter. They make very good houseplants and can be made to flower again the following year if the correct light conditions are observed.
Indoor grown cyclamens need a moist soil (but not waterlogged). Water them from below to prevent water pooling on the top of the corm, where it can easily cause rotting. They thrive best in a cool room or hallway where the temperature is kept at or just below 16°C (61°F).
Bowls or flowering bulbs are also popular, such as hyacinths, daffodils and tulips. These will have been specially treated and forced into early bloom for Christmas. The flowers last surprisingly well if the soil is kept moist, and the room where they are on display is not too warm or stuffy.
The bulbs are tricked into early flowering by adjusting their growing conditions. This is a task best left to the experts and these specially 'prepared' bulbs are usually available for sale in garden centres around August and September.
The bulbs are planted into pots or bowls of moist bulb fibre. Then kept in a dark, cool place for about three months, before finally bringing them into the light and warmth to encourage flowering.
Prepared bulbs suitable for forcing include:
• grape hyacinths
• reticulata irises
If you are planting your own prepared bulbs, choose a container at least 4in (10cm) deep and 6in (15cm) wide. This will hold three hyacinths, six narcissi or tulips, or 12 smaller bulbs like crocuses. Allow about 12 weeks for narcissi and hyacinths, 14-15 weeks for other bulbs.
Once the flowers have died the bulbs can then be planted out in the garden, where they should flower next year as normal. As with all bulbs, the leaves should be allowed to die back naturally.