Amaryllis can grow and flourish outside in Sunset magazine's climate zones 13, 15-17, 21-28, H1 and H2 (see Resources), but many people in colder climates like to force amaryllis bulbs to bloom indoors, particularly during the Christmas season. You can buy amaryllis bulbs in nurseries and home improvement stores in the fall, just in time for forcing.
Plant your amaryllis bulb in a heavy pot with a diameter of 6-8 inches.
Fill the pot about two-thirds full with potting soil.
Turn the bulb so that the pointed end is facing up, and put it down into the potting soil. Cover it so that only about two-thirds of the bulb is under the soil.
Set the pot into its watering saucer and water the bulb thoroughly. Leave it alone for a quarter of an hour and then throw away the water that's standing in the saucer.
Find a bright spot for the pot, but don't put it in direct sunlight.
Check the bulb every few days for moistness by sticking your fingers into the soil close to the bulb. If it's no longer damp, water it again.
Each time you water, let the plant drain into the saucer and discard the water. Nothing will kill an amaryllis more quickly than leaving its roots standing in water, which promotes root rot.
After the plant begins to send out leaves, give the pot a quarter turn every day to make sure the stalks don't bend toward the light.
When the plant begins to sprout buds, insert a flower stake into the pot behind, not through, the bulb. Using gardener's tape, tie the stalks to the stake very gently, so as not to bruise them. Usually the plant will start putting on buds 3-6 weeks after you've planted it.
When the blossoms of the amaryllis dry up, take them off the plant very gently to encourage it to put out more flowers.