Barely have you started to plant your spring-flowering bulbs, and it’s already time to think about the winter and how to replicate these blooms indoors, without spending a fortune.
The answer is to ‘force’ bulbs into flower – that is give them assistance to bloom far earlier indoors than they would normally outside.
Garden centres should now be stocking up on bulbs which are sold specifically for forcing, which may include fragrant hyacinths, large-flowered crocus, hippeastrums, miniature daffodils and a few tulips, which should be marked ‘prepared’ in the shop.
By growing bulbs indoors in a warmer atmosphere than they are accustomed to in the garden, for all or part of their growing season, they’ll grow quicker and flower earlier than they would otherwise. However, if you bring them on too quickly, they may fail.
You can use any type of pot because indoor bulbs can manage without drainage, as they are being grown for such a short time, provided the container holds enough compost to accommodate the bulbs. It’s worth spreading a layer of gravel at the bottom of the pot to help drainage.
For best results go for bulb fibre when growing bulbs in containers with no drainage, as it has plenty of air space and often contains added charcoal which keeps the compost fresh, even if it becomes too moist. Alternatively, you can use multi-purpose compost.
Prepared hyacinths are the most popular bulbs for forcing and generally go on sale at the beginning of September, after being given a couple of weeks of cold treatment to make them think they’ve gone through winter.
Whatever you do, don’t leave prepared bulbs for a few weeks in a warm environment before planting, or they will lose the cold effect they were given initially. Instead, store them in a cool, dark place and plant them by the middle of September if you want them to flower by Christmas.
For the best effect, plant bulbs of the same colour together. They should be planted close together on top of a depth of at least 6cm of compost, so they are not quite touching one another. Then fill the bowl to just below the rim with compost, so their growing tips are just sticking out above the surface. Don’t firm the bulb fibre down or it may hinder the root system establishing quickly. Make sure you don’t overwater them, just water the compost lightly.
Place the container in a cool, dark place such as the shed or a closed cupboard in a cold room for 10-14 weeks, to encourage the flowering stems to develop before the leaves. It also enables the root system to become well-established. If the bulb fibre becomes dry at any time, water carefully between the bulbs.
Don’t hurry them, because insufficient time in the dark will result in stunted flowers or failure. When the leaf shoots are around 1-2in (4-5cm) high, move the container into a cool, light room.