Modern plants (Angiosperms) create flowers as a way of expressing their sexual reproduction. These vary immensely in
their shape, color, size, and even pertinent parts! Primitive plants – ferns, mosses and conifers do not produce flowers.
We say a flower is “complete” when it has all the parts necessary for reproduction. They are also called “bisexual” or
“hermaphroditic”. In addition to colorful sepals and petals, it has stamens – the male part which contains pollen (sperm),
and a pistil/ovary – the female parts with the ovule (egg). A fertilized ovule becomes a seed. Hibiscus is a good example.
Not all plants have flowers with all the parts! Some form either male or female flowers – we call these “unisexual”.
Squash and Begonias are such examples. Look closely and you can see the ovary below petals in the female flowers
If both male and female flowers are produced on the same plants – we call those plants “monoecious” – like in birch with
its two distinct catkins, or melons, cucumbers and pumpkins.
If the male and female flowers are produced on separate plants we call those “dioecious” – like in holly. BTW –
Dioecious comes from the Greek – meaning two households.
Confused yet ? Wait. There is a myriad of combinations and exceptions as well! Aghhhhhh !!!
Some plants change the sex of their flowers over time, This is called “sex switching”. Young plants produce mainly male
flowers but as they age produce mainly female flowers. Case in point – Jack in the pulpit.
My favorite plants are the “Androgynomonoecious”. They covered all bases by having male, female and bisexual
flowers on the same plant! Note: also called “polygamomonoecious”, or “trimonoecious”. This occurs in papaya.
Are we there yet? One more thing. Outcrossing or cross-fertilization. Meaning – you cant self pollinate / self fertilize –
also known as “self-incompatibility”.
In higher plants It eliminates damaging recessive mutations as its unlikely the other plant has the same one. It also
increases the genetic variation which helps the offspring with adaptability in other environments.
“Allogamy” also avoids self pollination – its when male / female parts of a bisexual flower mature at different times.
Anatomy of flowering plants not your thing? Just enjoy the beauty in flowers – next time you see one – take a closer look !
SEXUALITY IN FLOWERING PLANTS – its complicated !
Written by Peter Morris our resident Horticulturalist