Outdoor America 2020 Issue 2
The USDA Forest Service defines pollination as “the act of transferring pollen grains from the male anther of a flower to the female stigma.” It’s the first step toward making seeds.
Though pollinators, like butterflies and bees, might spread pollen from more than one type of flower, only the pollination from one plant to another of the same species can cause that plant to successfully reproduce. In addition to insects, pollen can move from flower to flower by wind, water, birds, bats and other animals. According to the Forest Service, about 80 percent of pollination involves animal pollinators, versus 20 percent by wind and water.
DID YOU KNOW?
75 percent of the world's flowering plants and 35 percent of the world's food crops depend on animal pollinators to reproduce.Source: Natural Resources Conservation Service
Flowers attract pollinators via petal shape, scent and color. Butterflies and bees like shallow or tubular flowers that give them a place to perch. Flowers that smell fetid to us are alluring to beetles, and hummingbirds hover by red blooms. None of these creatures spread pollen on purpose. Pollination is merely an inadvertent result of their feeding habits. When a bee sips energy-packed nectar from a flower or when a butterfly drinks protein-rich pollen, pollen grains attach themselves to the bee’s or butterfly’s body. When that insect lands on another flower, the pollen grains fall onto the flower’s sticky stigma.
When pollen adheres to a flower’s stigma, a pollen tube forms into the ovule of the flower. When this happens and fertilization is successful, the plant produces seeds or fruit containing seeds. Sometimes a plant can be only partially fertilized which results in underdeveloped seeds or fruit, and sometimes, pollination doesn’t work.
Some plants can self-pollinate without the help of an animal pollinator. This is a helpful way to reproduce when an ecosystem does not have many pollinators, where the growing season is short or where only a limited number of plants can grow. The downside of self-pollination is lack of genetic diversity. Flowers that can self-pollinate include lilies, roses, sunflowers and most annual flowers.
Some plants, like corn, can self-pollinate and cross-pollinate (pollinate with another plant). Others only cross-pollinate. Cross-pollination ensures genetic diversity, which usually translates into better disease resistance.
No one knows the true origin of the word "pollen" which means "fine flour" in Latin.
Plants that only cross-pollinate have a variety of strategies to prevent self-pollination. A plant might produce separate male and female flowers which appear at different times, or it might have physical barriers that prevent self-pollination. For example, geraniums shed their anthers before their stamens appear, making it impossible for them to self-pollinate.
Certain flowers have evolved such that only a specific type of pollinator can help them reproduce. Usually these flower species have a specific shape, like closed bottle gentian which look like blue balloons. Bumblebees are the primary pollinators of closed bottle gentians because they are one of the few insects that can push their way into the bottle.
Some bees are known as buzz pollinators. When one lands on, say, a wild blueberry blossom, its vibrations loosen the pollen, which attaches to the bee.
Other flowers have specialized tricks to attract pollinators. Skunk cabbage, an early blooming wildflower, produces an enzyme to warm itself, which also melts its surroundings. Flies and beetles come to it for a meal and a warmer place to hang out.
Want to see pollinators in action? Grow native wildflowers in your backyard. You’ll not only have a beautiful garden but also attract a plethora of pollinators depending on what you plant.