Tuesday, January 26, 2010

So you like birds and butterflies? Better make room for Caterpillars!

When I started my project on the use of North American native annuals and biennials in Residential landscapes, I began to list some reasons for using native plants. This list included the particular benefits of annuals and other short-lived species that come with the greater emphasis on reproduction, resulting in more pollen, nectar and seeds. To be successful these are dependent on the pollinators gardens, the butterflies and bees that so many gardens wish to attract to their.

After a little more thinking and reading books like ‘Bringing Nature Home’ by Douglas Tallamy and Sara Stein’s ‘Noah’s Garden’, I began to appreciate that if you want butterflies, there must be a place for caterpillars nearby. Caterpillars are not only the source of butterflies; they are also an important source of food for birds. Insects, particularly herbivores, are a major component in the diet of nestlings.

Douglas Tallamy points out that most species of caterpillars are specialists, in that each has evolved to eat only a narrow range of plants – ones that they have co-evolved with for many thousands of years. Exotic and non-native plants ( ones that have not shared an evolutionary history) are of little use to these specialists. The bottom line is that most native insects need their own native food plants to survive.

Another aspect to nurturing pollinators is for the gardener to develop a tolerance for leaves with a few holes in them, and not to run for the pesticide at the first sign of attack by these native herbivores. In an ecologically balanced environment there are sufficient predators that will keep the caterpillars and other herbivores in check. Take a look at some websites or blogs on organic and habitat gardening approaches, such as the National Wildlife Federation (www.nwf.org/In-Your-Backyard.aspx) or http://www.ecosystemgardening.com/ , to learn more about creating a fully functional habitat garden.

Here's an example of a caterpillar infected with  parasitic wasps.

To learn which native plants support a given species of caterpillar/butterfly, check out the appendices in ‘Bringing Nature Home.’ Also the website for Butterflies and Moths of North America (www.butterfliesandmoths.org/ ) lists many facts about butterflies and moths found in North America, including their host plants for their larvae. (This site is searchable by insect’s species and state; doing the reverse, to find a list of insects feeding on a particular plant is not trivial.) The Wildflower Center’s website lists some plant-insect relationships in with their plant descriptions.

I’ve heard a little bit about putting sacrificial plants in the back of the garden to draw herbivores out of the more ornamental parts of the garden. Has anyone out there had experience with this approach?

As more native habitat is converted to human use, incorporating native plant species into the residential landscape is a step in the right direction toward supporting out native wildlife.


tina said...

It makes perfect sense to me. I guess I have to deal with those caterpillars eating some of the plants in order to have the flying flowers. Very well written and informative post.

. . . Lisa and Robb . . . said...

I wonder how many people just don't "get" this. I read about so many garden bloggers putting Bt everywhere...