National Pollinator Week: Insects and Trees
It’s National Pollinator Week! A pollinator is an animal that moves pollen from the anther of a plant to the stigma, which brings about fertilization of the plant. People often think of pollinators and flowers, but did you know trees need pollination, too?
Nearly all of the conifers in our area including pine, spruce, and hemlock rely on wind pollination. Broadleaved trees like birch, cottonwood, elm, oak, and walnut rely on wind pollination, too. However, there are many trees that rely on pollination by insects (as well as birds and bats in some parts of the U.S.) because insect pollination is more efficient and direct.
Among the best known insect-pollinated trees are apples, basswood, cherries, black locust, catalpa, horse chestnut, tulip tree, and the willows. Just to name a few! These trees tend to have fragrant (sometimes even stinky), large, or otherwise showy flowers that attract the pollinators either by sight or smell. The pollen produced by these trees tends to be slightly sticky, less dust-like, and produced later as the leaves are forming.
The most important insect pollinators are flies, beetles, moths, and butterflies. Particularly important is the order known as Hymenoptera, which includes bees.
Using insects for pollination is a bit more targeted approach than wind pollination. Nevertheless, flowers that rely on insects need to make an investment to ensure successful fertilization. They must advertise themselves, reward the pollinator, and provide a suitable landing spot. They must also make sure that pollen is transferred onto the insect.
Regardless of wind or animal pollination, the goal is to produce seeds (in the form of cones, fruits, nuts, and berries) that will germinate new trees for many generations to come. But in the end, it all starts with pollen. The next time you see a beautiful flowering tree, be sure to thank the pollinators!
If you’d like to learn more about the trees around us, consider taking a Tree ID Walk with Tree Pittsburgh! Teachers, check out our Teacher Resources page for lessons as well as opportunities to have Tree Pittsburgh visit your school to talk about pollinators and more.