Physiology and Growth.
Hippeastrum is a so-called tunicate bulb, which is a description for bulbs which form a protective tunic from dried-up outer scales. The inside scales are usually white, but with a yellow discoloration at the base above the roots. This is the stem tissue, also called the basal plate, which is capable of developing new roots, flower scapes, and leaves.
During a normal growth cycle, 8-12 leaves will develop within these scales and grow out through the nose of the bulb. For every 3-4 leaves, a flower scape is also developed inside the bulb.
It takes approximately 18 months from the development of a scape until flowering. E.g. when the bulb is finished flowering there is actually another scape inside the bulb which will not grow and flower until the next season.
Hippeastrum is hardy in gardening zone 7 to 11. Northern gardeners can bring the bulb indoors in winter to grow on, or simply induce dormancy by withholding water. If stored at a temperature of 40-45 F (5-7 C) it can be kept in "animated suspension" until growth and flowering is desired. If potted during this period the bulb should be watered occasionally to avoid dehydration.
Forcing into Flower
Contrary to common belief, Hippeastrum does not require a dormancy period similar to that of tulips or lilies for example. The plant will continue to grow if conditions are favorable, and eventually flower on its own. However, if temperatures are too low, the leaves will wither and the plant will enter a state of dormancy. This period of inactivity stimulates development of the scapes inside the bulb and they will start to grow and as soon as favorable temperatures and moisture conditions return.
Gardeners can capitalize on this defense mechanism to program flowering. Withhold water in July and the leaves will turn brown and wither. This induces a forced dormancy. Let the bulb rest in a cool, dry place and by November the flower scapes should appear at the nose of the bulb which can then be brought out and watered. The plant should flower in 6-8 weeks. Hippeastrum can be induced to flower at any time of the year but sufficient time must be allowed afterwards for vegetative growth before inducing dormancy again.
