First it helps to know what you're even looking at, as in, what is a bulb?
A bulb is, essentially, a compressed plant stem (baby plant) surrounded by modified leaves. An onion is a bulb. You know how, if you leave onions in the fridge too long, they start sprouting? That's because they're bulbs.
Amaryllis are also bulbs, and if you cut one open, it will look a lot like the inside of an onion!
Tucked inside the bulbs are fledgling plants complete with flower stems, blossoms and foliage, all just waiting to get out. Given warmth and just a little water to wake them up, they'll sprout and grow, drawing from the nutrient layers to fuel their initial activity. This is why it's not necessary for amaryllis to have extensive roots to produce their first set of blooms.
When you buy a bulb it basically has everything it needs inside of it in order to grow. Some bulbs have "chilling" requirements. Others need a dormant period to rest. When you buy a new amaryllis bulb in the fall, it is ready to be planted and will sprout a flower stalk (or two).
After your amaryllis stops blooming, you'll want to set it in a sunny windowsill so that it gets plenty of light. You'll see long, straplike leaves emerge. At that point, the Amaryllis becomes a nice, green houseplant. The leaves will photosynthesize (Who remembers that from school?) and make food to store for the next year's blooms. Keep watering the amaryllis bulb as you did when the bulb was flowering, keeping the soil about as damp as a wrung-out sponge.
If you live in a warm climate (zone 8 or higher) you can plant your amaryllis bulb outside when it is finished blooming. In cooler regions you'll want to let your amaryllis grow through the summer and then give them a rest in the late summer and early fall.
For more information about how to get your amaryllis to re-bloom, click here.
Ready to grow your own amaryllis?
I leave my plants in the ground year round. I am located in central east Florida, so the weather stays pretty good year round. I get blooms every year at Easter and greenery the rest of the year. I am a happy gardener.