© Janet Davis
Birds
do it, bees do it, even educated sweet peas do it ....
If the plant world worked the way the animal world does, we might have had different lyrics to that old Cole Porter song. Fact is, sweet peas—unlike “educated fleas”—don’t need to waste time falling in love. Why should they, when they can get right to the sex part?
There’s no blushing in the flower border, no awkward preliminaries, no beating around the bush. Sex in the plant world is the horticultural equivalent of a red-light district: It goes on 24 hours a day, is wildly promiscuous, involves unlikely partners—and it’s all business. The business of pollination.
When I use my closeup
lens to photograph the brief visits of pollinating insects to the blossoms in
my garden, I’m completely captivated as I watch my favourite flowers soliciting
customers for sexual favors.
If you don’t spend a lot of time observing this process closely, you might think the job falls entirely to honeybees, bumblebees and butterflies. While important pollinators, they’re only part of the gang. Early in spring, it’s more likely to be hoverflies (or syrphids, as entomologists call them) doing the deed. Stand near a forsythia or fragrant Farrer’s viburnum early in May and you’re almost guaranteed to see one of these striped black-and-yellow insects zooming in and hovering over the blossoms. Later, it might be their cousins, the droneflies, busy nectaring in asters or mums. Other pollinating insects in the northeast include carpenter bees, alfalfa leafcutter bees (shown at left), solitary mining bees, virescent green metallic bees, yellowjackets, hornets and numerous beetles.
Different plant species use wildly different means to achieve the same result: Transfer of pollen from the male flower anthers to the receptive stigma at the end of the style, the female portion of the flower that leads to the ovary. The plants may be self-pollinated, meaning the fertilizing can be done within the same flower or on different flowers on the same plant, or they might be cross-pollinated, meaning the pollen must travel to a stigma on a flower of the same species, but on a different plant. From there on, it’s fertilization, seed-making and survival of the species. Just like us!
Through the ages,
flowers evolved by developing symbiotic relationships with the animal world.
Some of the earliest and most simple
blossoms, the saucer-shaped magnolias, are known to date back some 110 million
years to the Cretaceous period, their ancestral fossils having been found in
Labrador. They were then, and continue
to be, pollinated by beetles (which evolved long before honeybees and their
kin) looking for sweet nectar to eat and inadvertently transferring pollen from
the anthers to the stigma. Pollen grains are specific to each type of plant;
rose pollen can’t germinate on the top of a sunflower’s stigma and create a
rose-sunflower cross.
As flowering plants diversified, they developed characteristics that would facilitate pollination by insects or birds native to the same region, something Charles Darwin called “natural selection.” Eventually the huge family of composites evolved, containing all the daisies and thistles that get pollinated by bees, flies and butterflies. Daisies have two-part flowers: Colorful but sterile flowers or “ray florets” on the outside to attract the insects and tiny fertile flowers or “disk florets” on the inside. Plants like the strawflower and black-eyed Susan in these photographs offer a flat landing pad that encourages longer insect visits while offering up lots of sweet stuff buried in the numerous disk florets.
And that, of course, makes nectar-gathering worthwhile for the insect and pollination a sure thing for the plant.
Adapted
from a column that appeared originally in the Toronto Sun.