You keep the water just at root level, not touching the actual bulb, so you need to top it up every few days and replace it completely every week.

Water/ Hydroponic culture;

Select a narrow necked container in which the roots will have space to grow and in which the bulbs will rest without falling into the water.

Special glass bulb jars with constricted necks, are available from good garden centres.

Circa Week 33-35; Fill the jars with tap water to 12mm( ½") above the neck then start the bulbs into growth by placing a bulb on top of each jar, ensuring that only the base of the bulb is in water.

Note; the bulb will rot if it is completely immersed.

Place the prepared jars in a dark, cool, frost-free place.

Check periodically to ensure that the base of each bulb remains in water until the roots emerge.

There after ensure that the roots are always in contact with the water.

When the roots are 75-100mm (3"-4") long and the leaves have grown at least 25mm (1") move the jars into a warmer location, e.g. a greenhouse or to the window sill of a cool room.

When the leaves are about 50-75mm (3"-4") high; raise the temperature gradually to 16°-18°C (60º-65°F).

Bulbs grown in this manner will tend to shrivel through lack of nutrients rendering them useless for further use.

The bulb could be planted out in the garden after being forced, but it will have a low chance of survival, and it will probably be around 2-5 years before it blooms again. Even if it does bloom again, don't expect the big columns of flowers again: without special treatment, they will produce blooms more like wild bluebells.