The technique recommended for years has been growing the plants on through the summer outdoors, and then inducing dormancy by stopping watering in the fall and placing them in a dry cool spot indoors for 10 to 12 weeks. The reason for this is to try force blooming for a specific period, usually Christmas.
However, for bigger, healthier plants, some experts recommend allowing the bulb to continue growing vigorously as long as possible, so it will reward you with better blooms in January or February.
To encourage your bulb to rebloom, just follow these six steps:
Once the flower is finished, cut off the stem just above the bulb nose. Give amaryllis bright light on a sunny windowsill or under plant lights. Feed and water. Apply a standard water-soluble houseplant fertilizer at half the recommended strength every two weeks.
Keep bulb in a pot sized “just right”. As the bulb grows and the pot fills with roots, move it up to a bigger pot that’s just slightly larger than the bulb. I like to use tall, narrow clay pots.
In summer, move the pot outdoors into a sunny spot and treat it like a container plant. Continue fertilizing until the middle of August. Don’t allow the soil to dry out, but avoid keeping it soggy.
In fall, before there’s a chance of frost, bring the plant inside and place in a sunny window or under plant lights. The leaves may yellow and die off by late December. During this time, keep the plant moist, not wet; most importantly, don’t let the pot dry out. The buds for the new flowers should appear in January or February, but sometimes they bloom as late as March.
After flowering, resume feeding and keep the pot in a sunny window or under plant lights until it can go outdoors again. Big vigorously growing bulbs will produce offsets – little baby bulbs – which you can pot up to grow to flowering size in a couple of seasons.