July is probably the highlight of color in my backyard garden, and what a feast for the eyes upon my return! As I passed by the potted hibiscus that gets moved outdoors for the summer months, I noticed quite a few brilliant red flowers had just opened.
This is the tropical red hibiscus that is so popular as a house plant and a favorite of plant breeders hoping to create a new color variety.
Interestingly, red hibiscus is no longer found in its original native (Asia) habitat, but has been introduced all over the new world tropics where it typically grows into a tall shrubby hedge. Hummingbirds and other nectar-lovers visit the flowers, but do they really pollinate it? No one seems to know the answer. It’s a very large flower, and the pollen-containing anthers are well separated from that 5-pronged stigmatic surface, so one would think something larger than a hummingbird must do the pollen transfer from flower to flower.
Such a beautifully constructed reproductive structure deserves a closer look.
The stamens (male) grow right out of the style that terminates in those 5 fuzzy-ball looking stigmatic surfaces (female). You can see a few pollen grains sticking to the hairs below the stigmas. One ball of pollen seems to be floating in air.
The anthers supported on slender pink-red filaments are full of yellow balls of pollen. It doesn’t take much more than a shake of the flower to dislodge the pollen, but gravity causes it to fall down into the base of the flower, not out toward the stigma.
It looks like the stigma traps errant pollen grains with those long hairs on the ends of the style. The fuzzy surface of the stigma must make it difficult for pollen to make it down to the actual surface to germinate.
Red Hibiscus are apparently self-fertile, but the plants only resort to “autonomous self-fertilization” after a certain length of time, in order to permit pollen transfer from other plants to occur. However, these flowers don’t last much more than a day in my garden, so pollinators would have to respond quickly to do the plant’s bidding.
What marvels we find when we look up close…
Back Yard Biology 