Amaryllis bulbs are one of many species of bulbs that can be forced or sped into bloom by exposing the root plate to constant contact with water. Amaryllis bulbs are not forced in water as frequently as other bulb species such as hyacinth or narcissus due to their much higher cost. Once forced in water, all of the bulb's nutrients are depleted and they must discarded as they will not grow or re-bloom if planted in soil. Though a bit expensive, amaryllis bulbs will readily produce their spectacular display when forced in water.
Fill a forcing vase large enough to hold an amaryllis bulb with water so that the waterline sits just above the neck of the vase. Fill the jar or narrow glass bowl with water to the top.
Test set the bulb into the vessel to see where the water hits the bulb. Adjust the water level up or down until the water coats the root plate of the bulb but goes no higher. Replenish the water as needed every day or three to maintain this level throughout the forcing period. Once the roots have developed, you can allow a few more days between replenishing the water as the bulb can drink from the roots. Change the water entirely at least once a week.
Place the bulb vase setup in a cool low-light spot in the house. It need not be a completely dark room, just low light away from windows. Move the vase to a location with bright indirect sunlight when green leaf shoots begin to pop out of the top of the bulb.
Keep the amaryllis out of direct sunlight to prolong the life of the bloom. When the flowers finish and die back, you can throw away the bulb and start another in the clean vase with fresh water.