By Barbara Walvoord
First published in the Lathrop Lamp Post for June 29-July 5, 2019
Foxglove beardtongue (Penstemon digitalis), blooming now at Lathrop, has some very clever devices for getting itself pollinated.
First, produce an enticing white flower that advertises to bees—“Nectar and pollen here! Get yours today!”
Then make that flower tubular so the bees have to crawl inside to get the pollen and nectar. Put purple lines inside the tube to guide the bees to your goodies.
Then practice gender fluidity: first you’re a male flower, then you’re a female flower.
When you’re a male, you have 4 stamens sticking up at the top of the tube, each loaded with pollen. When the bee comes in to get the nectar and pollen, the pollen brushes onto the top parts of its body—parts that are not easily groomed off. So now the bee has eaten some of your pollen and carried some to its nest, but there’s probably some left on its body.
As a backup, a fifth male stigma sticks out at the bottom. It’s shaped like a tongue and covered with hairs like a beard (hence, “beard tongue”). It’s sterile, but its hairs are ready to catch any pollen that falls on it, and deposit that pollen on the body of any bee crawling around inside the blossom. (Your scientific name, Penstemon, reflects your five stamens.)
Now–oh so clever–you become a female. The stamens dry up and in their place you put your female organs, nice and sticky, to catch the pollen. Then when a not-so-cleaned-up bee, with pollen still on its body from some male plant, comes to get some of your nectar, the pollen brushes off onto your female organs, and voila! Pollinated!
You have ensured that more foxglove beardtongues will delight us humans with their beauty, feed pollen and nectar to bees, and offer their leaves to eight species of butterfly and moth caterpillars, which our birds need to raise their babies. That’s only a tiny part of the wonderful story of the birds and the bees at Lathrop.