Depending on the size of the amaryllis bulb, it blooms more than once each season. Large bulbs often send out more than one flower stalk at a time or a few weeks apart.
DavesGarden.com provides a few tips for growing large amaryllis bulbs, which produce multiple flower stalks next season. It recommends after the initial flower stalk is spent, cutting down the stem close to the bulb making sure to keep the leaves. Providing bright sunlight, water and fertilizer throughout the summer encourages continuous leaf growth. DavesGarden.com suggests that the more leaves the amaryllis develops, the more blooms it sends up the next spring.