Flowers on a few plants are either male or female; other flowers are both male and female components. More rarely, flowers alter or pass through sexual periods, switching from 1 sex to the other. Protoandrous flowers begin as male blossoms and change to female. Protogynous flowers begin as females and transform into male. Fruit trees with blossoms that go through sexual periods include the avocado (Persea americana), the papaya (Carica papaya), the sugar apple (Annona squamosa) along with the paw paw (Asimina triloba).
The male stamen of a flower contains an anther, covered with sticky pollen, that sits atop a slender filament. The female stigma that receives the male pollen sits atop an earnest which looks like a mini fruit. Pollen has to be moved from the anther to stigma for the flower to be fertile and bear fruit. There are variations to the way those the male and female components appear when you look within the flower of a particular fruit, but these are the fundamentals.
Protogynous avocado blossoms open for 2 days, but having various stages of opening for male and female pieces. An avocado flower first opens as female for just two to four hours, exposing its stigma to insects posture pollen. On the next day the same flower opens as a man having a exposed stamen. In certain avocado varieties, the female flower closes early in the morning and closes in late morning or early afternoon. On the day of the next day it opens as a man. Other varieties available as a female in the early day, close in late day, and reopen from the male phase the next morning.
Papayas may bear female or bisexual flowers containing both sexes on short stalks or clusters of male flowers on clusters 5 to 6 feet long. Papaya flowers aren’t genetically programmed to routinely change sex, but also in hot summer weather immature or male flowers will occasionally change to females. If no male or bisexual flowers are neighboring to provide pollen, female plants may not yield papayas. Papayas are occasionally called paw paws, however they are not just like the North American paw paw (A. triloba).
The petals of this sugar apple, also called the custard apple, open marginally during the day revealing a glistening surface of the female stigma, indicating that it’s receptive to pollen. The blossoms open wide the next morning to reveal the brownish male anther. By late afternoon the anthers begin releasing pollen. The practical effect of sugar apple blossoms switching sexes by periods is that cross-pollination among distinct flowers is necessary, and they are often pollinated by hand to increase production.
The blossoms of this North American paw paw are protogynous. Their petals turn from green to purple and are tightly packed in the female phase; their sticky stigma are shiny and green. The shut petals force insects posture male pollen to brush against the stigma. Meanwhile, the man anther is tucked into a tight, ball. As the blossoms turn male, the petals open and turn a dark purple, and the blooms emit a strong odor. The ball of anthers opens along with the anthers turn from green to brownish. The open and scent petals invite browsing insects to enter and bump up against the mud on the anthers. The effect of the switching of sexes is that paw paws are self-incompatible, meaning that they need pollen from an unrelated paw paw tree. Pollination is further complicated by the fact that bees show no interest in paw paw blossoms; they are pollinated by flies and beetles. If no pollinating insects can be found, you need to pollinate paw paw blossoms by hand.