Amaryllis bulbs are warm weather plants that grow outdoors in USDA zones 8 to 10 or indoors in any zone. If you want your amaryllises to bloom again the next year, you will need to preserve--or store--the bulbs in a cool location to induce dormancy for the growth cycle to begin again. This is true for both indoor and outdoor plants.
Cut off the blooms after the flowers have faded to prevent seeds from forming and using up valuable nutrients that are needed for next year's blooms. Use clippers to clip just the flowers off. Leave the flower stem and foliage on to absorb sunlight and make next year's food to be stored in the bulbs. Cut off the flower stem when it starts to droop.
Wait until the fall when the leaves turn yellow and cut it back to 2 inches above the ground. For indoor plants, the foliage will not turn yellow in its current location, therefore you have to force it. In September, place the pots outside if it's cold or move them to a dark, cool location, such as your garage. The lack of light and slight temperature change will cause the leaves to yellow.
Remove the bulbs from the soil. Amaryllis bulbs are usually planted just below the soil's surface. Carefully use a trowel to dig straight down several inches around the stem of the plant. Then, pull down on the handle to lift the bulb out of the soil.
Shake off and remove as much soil as possible with your hands. Clean the bulbs with water and allow them to dry. Then, place them in a paper bag, mesh bag or open container for storage. You do not need any soil.
Store the bulbs in a cool, dry location, such as a garage, attic or crawl space. A temperature around 50 degrees F is ideal. You can even put the bulbs in the refrigerator, but don't store them in the same area as any apples, which can cause sterilization.
Preserve the bulbs for about 8 to 10 weeks, at which time you can replant your amaryllis bulbs. If you want your amaryllises outside but it's still cold out, replant the bulbs indoors and move the pots outside in the spring after the last frost. You can then bury the pots or replant the entire plant carefully.