Native from the Himalayas westward to Iran, pomegranate trees (Punica granatum) appreciate intense heat in the summertime as well as exposure to abundant sunshine. In the U.S., grow pomegranates in acidic, neutral or alkaline soil across U.S. Department of Agriculture hardiness zones 7 through 10. Although these shrubs or trees tolerate drought, they will flower and yield more fruits if the well-drained garden soil is moist. Aside from moisture level, there are several other factors that impact the flowering--or lack of flowering--in a pomegranate tree.
Pomegranates produce their bright orange and orange-red flowers during the warm months. Depending on climate, that means blooming as early as mid to late spring if winters are warm and mild, or into the early summer elsewhere. If the balance of summer and fall remain warm, intermittent blooms may continue, although they may not form fruits before temperatures cool by winter's start.
Inadequate light levels are a central reason pomegranate plants fail to produce any flowers. A garden exposure that provides at least 8 to 10 hours of direct sun rays daily, especially from spring to fall is a necessity. The more sun and the warmer the growing season's temperatures, the better.
Pomegranates develop flowers on new growth. The American Horticultural Society's "A-Z Encyclopedia of Garden Plants" states pomegranates should only be pruned (if necessary) in late winter or very early spring when the plants are just ready to end their winter dormancy. Pruning the new growth, which is a coppery or red color maturing to glossy green, can diminish subsequent flowering. Removing too much new growth can remove the growth that would produce the first flowers of the season. Always prune the pomegranate to remove suckering shoots from the base that may shade more mature branches.
Besides inadequate light, other environmental stresses can reduce flower production in pomegranates. Soggy soils can reduce plant vigor and make it more susceptible to diseases, especially fungi. A late, untimely frost or freeze in spring can kill newly emerging stems and leaves. These damaged plants must regenerate new stems before they bloom, which could delay flowering for weeks. If the summer is cool and cloudy, such stems may produce fewer blooms. From spring to early fall, pomegranates respond well to regular watering and fertilizing.
According to Floridata, pomegranates begin to produce fruits after three to four years of growth and establishment after germination or sapling planting. This suggest flowering may not occur immediately if plants are too young--they are focusing on root and branch growth.