A nectary occurs on every flower as a large fleshy crenulate gland within the calyx and to which the stamens and pistils are inserted. Nectar, secreted only in the morning, is highly attractive to honey bees and flies. Size of the nectary and nectar sugar concentration followed a similar pattern. Anthers dehisce longitudinally. Fruit set occurs when pollen, primarily from M 2 flowers, is transferred to F flowers.
Fruit set in lychee is climate dependent and profoundly affected by temperature and humidity.
Reproductive failure is common and not always explained. In some years, certain cultivars produce few, or only male flowers and, as a result, little or no fruit is set. This problem can be minimized through the use of better adapted varieties and management methods to retard growth and induce flowering. These studies clearly show that Lychee requires insect pollinators. Moreover, hybrid fruit are heavier and have larger seeds, although the latter is not necessarily desirable.