Doug Tallamy, everyone's favorite entomologist/native-plant advocate, is one of the contributors to a new book about sustainable gardening (edited by Tom Christopher, and to be reviewed here soon). First he makes the case that if you care about insects, the birds that feed on them and, heck, all of nature, you'll grow some native plants, dammit, not just lawn and a few foundation plants. Nobody makes that case better than Tallamy.
He first made that case to the general public in his popular Bringing Nature Home, published in 2007, and he's had time to observe reactions to it and to the native-plant movement generally. For example:
There are many misconceptions about using native plants as landscape plants, but one of the most pervasive is the fear that natives will be defoliated by the very insects we are trying to attract with them. After all, that's one of the reasons "pest-free" plants from Asia and Europe appear to be the logical choice.
I've heard that one, but what I've heard and read much more often is the exact opposite claim – that native plants are the "pest-free" ones because they've evolved in harmony with the pests, etc. Which is hard to square with the urgings that we plant natives so the native insects can eat them, which they certainly do.
But guess what – both myths are wrong! According to Tallamy, native plants attract plant-eating pests but they also attract a diversity of predators, parasites and diseases that keep insect populations in check. Sounds great, but can he prove it?
Yes, indeed, he can. He convinced one of his grad students to make a study of insect damage, comparing "traditional" with all-native landscapes – six of each. After two years, the result was that only a tiny percentage of leaves were damaged on EITHER of the properties, with 1.5% of the leaves showing sucking damage and 4.5% chewing damage, both far below than the 10% damage threshold shown to be needed before homeowners notice it. And the difference between the native and mostly-nonnative landscapes was statistically insignificant.
This study not only levels the pest-damage field between native and nonnative plants but does it in a way that avoids the messy questions about whether the pests are native or nonnative. It simply records evidence from actual gardens in the 21st Century. Thank you, Dr. T!