Forcing hyacinth bulbs to bloom indoors is simple; it just takes a little patience. It can take as long as 13 weeks for the bulbs to come into flower.
Hyacinth bulbs require a period of cooling before they will bloom. Florist suppliers often have precooled hyacinth bulbs available, ready for forcing. If you can’t find those, just store the bulbs for 8 to 12 weeks in a cold frame, outdoor shed, garage, or other dark area with temperatures from 35 to 45 degrees F. It’s important that you don’t expose bulbs to freezing temperatures and if you put them in the fridge, don’t place them next to apples. Apples produce a gas that will cause the bulbs to rot.
Once the bulbs have been precooled, you can force them into bloom in almost any planting medium: potting soil, gravel and water or just plain water. To make it easy on yourself try using glass “forcing jars.” You can find these at florist shops, hobby suppliers or garden centers. They look like hour glasses with the tops cut off.
To begin, place the bulb in a glass container and add water up to, but not touching, the bottom of the bulb (about 1/4″ below the base of the bulb). Bulbs sitting in water are prone to rot. This is where the forcing jars come in handy because they are cinched at the waist and the bulbs sit nicely just above the water.
Place the bulb and jar in a cool, dark area (about 50 degrees F – a cool cellar, an unheated garage or a regular family-style refrigerator) until the root system is well developed and growth from the top has begun. Do not store these in a refrigerator with fruits, especially apples. As fruits and some vegetables ripen, they release ethylene gas, which can kill or damage the flower.
Keep cool for 10 weeks. Add water periodically, always keeping the level of water close to the base of the bulb.
When the shoots are about 2 inches tall and the root system extends to the bottom of the glass, remove the jars to an intermediate area that has low light and slightly warmer temperatures. Over the next 3-4 days, gradually move your jars into a sunny window.
When the flowers appear, keep them in bright, indirect light. Temperatures of 60 degrees F to 65 degrees F will ensure longest flowering. Turn the jar a bit each day so that the flowers do not lean to one side as they reach for the sun.