Answer: The most common reason for lack of bloom is lack of foliage growth during the after-bloom period, resulting in under sized bulbs. Larger bulbs will bloom best and the foliage is what will repower the bulb so it can bloom again. A rule of thumb is that four strong leaves are needed to produce a bloom stem the following season. Bright light, good soil and a long growing season will all contribute to ongoing amaryllis health.
Once the blooms fade, remove the bloom stem by cutting it off at the base. This prevents the plant spending energy on producing seeds. Your next emphasis is to keep the foliage growing and healthy by providing ample light and good care.
Some gardeners find that planting the bulbs out in the garden for the summer results in the most vigorous foliage growth. Other gardeners have good results by repotting the bulbs into fresh soil every other year or so. It is said that these bulbs prefer a slightly undersized pot, however if the bulb has made many offsets it may become too crowded and need to be repotted and/or have some of the larger babies separated off and planted in their own pots. Also, following a regular fertilization schedule during the foliage phase can also be helpful in maximizing the foliage growth. Using a fertilizer with "minors" included in the nutrient mix can also be helpful.
Finally, make sure that the foliage is allowed to ripen on the bulb; if should be dry and brown before you remove it each fall, allowing for ample transfer of energy to the bulb.
The bulbs usually need to rest dry and cool for about eight weeks prior to being watered and readied for blooming. During the resting period they should not be watered. Store them in a cool area (50 degrees)yet well above freezing. In early fall they should be dried out and rested, then repotted if needed and watered once lightly and set in a bright location to come back into active growth. Once growth begins, the soil should be kept slightly moist. You may also find over the years that the plant's natural rythm exerts itself and it naturally begins to bloom later in the spring each year.
I hope this helps you troubleshoot.
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