Sometimes, male flowers are produced initially by plants when
day-length is short. Later, as day-length increases, plants
will switch to produce mainly female flowers. Male flowers
are also induced by low temperatures, excess shade and excessively
close planting. Female flower production is promoted by warm
temperatures, and should occur later in the summer.
Female flowers can be identified by the swelling (immature fruit) at the base of the flower.
Absence of fruits when male and female flowers are being produced suggests pollination may be at fault. Try hand pollinating, where the male flower is rubbed against the female.
Fruits swelling only at the top, often with shrivelling and rotting, indicates incomplete pollination, usually due to cold temperatures. The problem should decrease as the season progresses. Also too many fruits on the plant can also cause rotting of small 'fruitlets'. This is the plant's way of balancing its resources; the problem can be alleviated by harvesting all usable fruits.
Helen Bostock