Tuesday, June 2, 2009
I've always thought that growing native plants is vaguely good - they're better adapted to the local climate and more apt to do well - but I never realized how important they are until I read this book.
Douglas Tallamy is an entomologist at the University of Delaware. In this book he explains that native plants support native bugs, who then support native birds. Simple, right? He provides numerous examples of plants - often touted as pest-free, and now I understand why - that may thrive in your garden, but that bugs avoid because they're not adapted to recognize them as food and couldn't digest them even if they did. The fewer the bugs, the less there is for the birds to eat.
Does this mean that a garden of native plants will be chewed up by the happy, hungry bugs? He claims not, citing a study that shows gardeners don't notice bug damage until it's reached more than 10% of the plant. Plus, if you plant a diverse group of natives instead of a monoculture, bugs can eat a little bit of many plants instead of all of just a few.
He also encourages everyone to reduce the space devoted to lawns - not a new idea, but he makes a compelling case when he points out that lawns provide the perfect habitat for Japanese beetles. Stop killing the grubs, just reduce your lawn!
Finally, he provides a rundown of the lepidoptera you can expect to support by growing native trees and shrubs. The white oak in the back yard turns out to be the perfect choice, supporting as many as 517 lepidoptera species! I had to rush over to the oak tree and turn over leaves in hopes of finding some of the caterpillars he mentions.
Which brings me to a caveat - though the text is inspiring and the photos gorgeous, why is there no scale (how big is that Luna moth, anyway?) and why is there no time frame (just when am I likely to find the yellow-shouldered slug caterpillar?).
The good news is that I've recently planted several natives, according to his helpful lists in the back of the book, fothergilla, clethra, oakleaf hydrangea, and sweetspire among them. And as I grub out more and more of the English ivy, I can make room for the Virginia creeper that "will enable the majestic Pandora sphinx to reproduce (by contrast, English ivy, the vine of choice in suburbia, hosts nothing)."
Notes to self: consider planting a native cherry, which supports giant silk moths and the tiger swallowtail butterfly, and put in several kinds of milkweed (asclepia tuberosa, syriaca, and incarnata) for color from June into September and the chance to attract 11 different butterflies. Also, forget butterfly bush! Yes, it provides nectar for adult butterflies, "but not one species of butterfly in North America can use buddleias as larval host plants. To have butterflies, we need to make butterflies." So there. Well, maybe I can tuck in just one to feed the grownups, as long as I provide the milkweed for the babies?