Why You Want Insects

Bringing Nature Home,
How You Can Sustain Wildlife with Native Plants


Gardening For Life
"Chances are, you have never thought of your garden - - indeed, of all of the space on your property - - as a wildlife preserve that represents the last chance we have for sustaining plants and animals that were once common throughout the U.S. But that is exactly the role our suburban landscapes are now playing and will play even more in the near future."

So says Douglas W. Tallamy, a professor of entomology at The University of Deleware. His Bringing Nature Home is an excellent book that explains as well as any source why we need to plant and preserve native plants.

He and other researchers have conclusive proof that insects prefer native plants. He has analyzed several species growing in his area with their area of origin. A eucalyptus might have over 175 insects that feed on it in Australia but few to none that feed on it in the United States and that's after being introduced more than 300 years ago.

Nurseries over the decades have encouraged homeowners to choose plants with are "insect free", but Tallamy explains how this is misguided.

Many might say, "But why do I want insects in my garden? Of course I deliberately purchase plants that insects don't like." This has been the view of many gardeners over the years and has resulted in a loss of bird life in our world. Birds need insects to survive, even if not normally insect eaters, they feed them to their young.

Tallamy and other researchers have examined plants for insect biomass on natives, and non-natives to an area. It is clear that insects are much more attracted to native plants - the leaf chemistry is very different from species to species even within the same genus. The plants have evolved this defense to protect themselves, and insects have co-evolved to be able to eat particular plant species because most insects are specialists. This may take hundreds, thousands, or even millions of years however. Many plants have been analyzed for the number of insects that feed on them in their area of origin as opposed to the area of introduction. It is clear in analyzing plants introduced into this country,that it takes more than 300 years for the insects to evolve to the point of being able to eat the new species.¹

At least two studies have been undertaken to determine if in fact the bird populations in native and non-native areas are different. One study showed a lack of bird populations where non-native grasses have been introduced, another showed that nestlings in an area with non-native plants were smaller and grew slower.

Do you worry that insects that might eat your natives, until there are none? If so, consider that all was in balance before we began introducing exotics (too many of which escaped into the wild and became invasives). Insects and plant diseases that go wild sometimes killing valuable plants seem to be always those in introduced (on purpose or accidentally by hitch-hiking on exotics) from other climes.

If you love wildlife, the introduction of native plants, or their preservation, seems very important. As Dr. Tallamy says, "A plant that has fed nothing, hasn't really done its job."

¹Douglas W. Tallamy, Bringing Nature Home, How You can Sustain Wildlife with Native Plants, (China:Timber Press, 2009).