Cherimoya flowers differ from most fruit species in their pollination method and attractiveness to potential pollinators. The flower is green and not easily seen unless you look carefully. They develop singularly or in groups of two to three on short, hairy stalks along the branches, continuing as new growth proceeds, and sometimes on old wood.
The fragrant flower consists of three long succulent petals surrounding the centre of the flower, which contains a cone shaped syncarpium of stigmas, the female structures that receive pollen and ultimately develop into fruit. The stigma is surrounded by several rings of larger grains called stamens, the male structures, which develop into pollen. Cherimoya flowers are hermaphroditic (the same flower has both female and male stages), but also shows protogynous dichogamy (the stigmas are receptive before pollen is shed by the anthers).
Flowers last approximately two days and open in two stages: first as female-stage flowers (lasting roughly 36 hours) and then as male-stage flowers. During the female stage the flower has a declining receptivity to pollen, and is unlikely to be pollinated by its own pollen in the male stage.
This chart is based on female-stage flowers with petals just beginning to separate:
Cherimoya flowers in various stages of development
In New Zealand, cherimoya flowers open and the stigmas are receptive early in the morning, but pollen is not shed from the male stage anthers until the evening of the second day. At this stage the stigmas are no longer receptive, which prevents pollination within a single flower, so
pollination by hand is needed to set a good crop.