When
purchasing hyacinths for indoor forcing it is essential to
buy bulbs that are specially 'prepared' for this purpose.
To have them ready for Christmas flowering they need planting
in September.
The bulbs need a cool (ideally 9°C/48°F), dark period to flower successfully. This encourages good root development and will take between eight and 10 weeks. Temperatures over 13°C (56°F) will result in excessively long leaves and either no or deformed flowers. Only when the shoots are 4-5cm (1.5-2in) long should the bulbs be brought into a cool but well-lit place for a few days to 'green up' before moving to warmer surroundings.
Too
much warmth immediately after removal from darkness can lead
to short-stemmed flowers or lack of flowers. Premature removal
and dryness at the roots are also common causes for disappointing
flowering. Overwatering may also cause bulb rot. If using
bulb bowls without drainage holes tip the bowl on its side
after watering to remove excess moisture. If using glass bulb
vases do not allow the water to touch the base of the bulb.
Preparation for future indoor flowering is not possible to replicate without controlled conditions. After flowering either discard the bulbs or plant them outdoors where they will often flower in spring for several more years.