Forcing hyacinths into bloom indoors – tricking them into flower earlier than they would normally bloom – is easy to do.
You can force them in a container in potting soil or by using just pebbles and water, or in glass jars.
Particularly attractive are traditional forcing glasses, which are hourglass-shaped so the bulb sits on top and only its roots are in the water.
Forcing hyacinth bulbs, cold period, timing
Development during forcing
The most important step is to give the bulbs the required cooling period that they need to grow roots. They need about 12 to 14 weeks at about 40°F (4°C).
Even when you buy hyacinth bulbs that have been pre-chilled, they will still need a period of cold treatment.
This will vary depending on how long they have been pre-chilled and can by four to eight weeks. (The instructions that come with the bulb should tell you.)
If you start your bulbs at the beginning of October, you can bring them out of the cold at the beginning of January, and have them in bloom three weeks later.
Forcing – step-by-step instructions
If you are using pebbles such as marbles or pea gravel in a container, set the bulbs on top of the layer of pebbles, which should be about two to three inches (3 to 7.5 cm) deep. Then add more pebbles, but leave the top one-third of the bulbs exposed.
Whether you’re using a container with pebbles, or a forcing jar, add enough water to create a moist environment for the roots, but keep the base of your bulbs out of the water, or they could rot.
If you’re growing your bulbs in containers with a potting soil mix, place individual bulbs together tightly, and again keep the top third of the bulb exposed. Water to moisten the potting soil.
Forced hyacinths grown in potting soil
Keep your container of bulbs in a dark, cool place for the required time, and add more water when necessary.
Once the roots have developed and leaves are actively growing, move the pot into bright light in a cool room where the temperature is about 65°F (18°C). At that point, it takes about three weeks for the bulbs to start blooming.
Popular varieties for forcing
‘Delft Blue’ – blue
‘Anna Marie’ – pink
‘Pink Pearl’- brilliant bright pink
‘Carnegie’ – white
‘White Pearl’ – white