Male Pawpaw tree (Carica papaya L.) producing numerous male inflorescences and few female flowers. Over time, one female flower successfully developed into a fruit. (located in Wanstead Garden, Saint. Michael, Barbados, West Indies)
A recent visit to a friend’s home yielded an unexpected botanical anomaly: a transgender Pawpaw tree (Carica papaya L.) or male tree that produces male and female flowers. It has been years now I have been waiting to witness this rare phenomenon firsthand—i.e., witnessing sexual reversal in a Pawpaw tree while observing abiotic and biotic conditions.
Papaya trees, renowned for their distinct sexual dimorphism, are trioecious species with three basic sex forms: female, male, and hermaphrodite. Male trees produce only male flowers or inflorescences, female trees bear solely female flowers, and hermaphrodite trees produce both. However, this particular specimen presented a fascinating deviation from the norm. Here we see a male tree producing female flowers, of which one flower successfully developed into a fruit.
The origin of these two Pawpaw trees remains uncertain. The property owner believes they may have sprung from discarded seeds or been dispersed by birds. I searched for other Pawpaw trees in the area and did not observe any within a 500-meter radius. Notably, these trees are located at the top of a hill and receive rainfall as their sole water source, with no artificial irrigation or fertilization. Under stressful conditions, such as limited water availability or nutrient deficiency, dioecious male plants have been speculated to undergo sex reversal as a survival mechanism, shifting resources towards seed production for increased reproductive success. However, this is not the only speculation surrounding this phenomenon.
Limited biotic observations were made during my visits, therefore, I was unable to identify any useful interactions or impacts. I was, however, able to note the presence of Apis mellifera c.f. (honeybees) and black flies (Simuliidae) as potential pollinators. To add to my excitement was the questionable neighbouring Pawpaw tree (?) which refused to reproduce; further emphasizing the unique nature of this observation. What is going to happen to this questionable tree under the existing conditions? Why hasn’t it reproduce as yet? When would it reproduce? Is it waiting for an environmental cue to trigger flowering? Would it be another male or perhaps a female or hermaphrodite? Would it even reproduce or die?
Observations made on male Pawpaw tree (Carica papaya L.)
located in Wanstead Garden, Saint. Michael, Barbados, West Indies.
(a) Complete Pawpaw tree (naturally grown to the side of staircase)
(b) Long pendulous inflorescences with spoon-shape buds showing fused petals
(c) Developing trumpet-shaped Pawpaw fruit
(d) Crown of Pawpaw tree showing young leaves, emerging leaves, and apical bud
(e) Characteristic long floral stalk of male Pawpaw trees
The widespread perception that male papaya trees have limited utility is inaccurate. For example, the flowers are rich in bioactive compounds such as antioxidants, vitamin C, and fibre and have been recorded to provide numerous potential health benefits.
This observation serves as an important reminder of the inherent variability and adaptability found within the natural world of plants. It underscores the importance of continued observation and research in Pawpaw diversity biology (sexual plasticity), which can be useful for agronomists, farmers, researchers and numerous plant breeding programmes.
