These days, I can't imagine why I planted that bank of hydrangeas along a sunny back wall, except that their puffy blue flowers are gorgeous and they remind me of my grandmother.

After hearing a talk by Doug Tallamy - and realizing how little my nonnative hydrangeas do for the insects and birds in my yard - I regret the ample real estate I gave them.

Tallamy, a University of Delaware entomologist, has become almost a phenomenon, a poster prof, if you will, for the ecovirtues of native plants. Sure, a specimen from China, or even California, might grow nicely here, but if it isn't from here, it matters.

Tallamy gave a talk recently hosted by the Schuylkill Center for Environmental Education, and 130 people showed up. Mike Weilbacher, executive director of the center, wasn't surprised at the interest. Word's been going around. "Once you see his lecture, you can't garden the same way again," Weilbacher said.

Tallamy starts out with a grim picture - the rampant loss of biodiversity. Many think of extinctions as involving exotic and faraway species like pandas and rhinos, but we miss the declines in our midst. Localized losses can happen quickly - as when Tallamy was a boy in New Jersey and, in a single day, a bulldozer covered up a nearby pond that had been filled with toads. No more toads in the neighborhood. Instead, the new neighbors planted a lawn.

That's typical. By Tallamy's count, U.S. lawns fill a space eight times as big as New Jersey.

If we're not planting lawns, we're decorating our yards with nonnative species, such as Norway maples and azaleas.

The problem with all this is that our insects have evolved to eat our native plants, our birds have evolved to eat our insects, and so on. They're picky eaters. If we give the bugs and caterpillars only nonnative species, like hydrangeas, they will have no food.

And we'll lose diversity, starting with the insects.

Alas, this doesn't bother many people. "We truly don't believe we need other species around for our own well-being," Tallamy says. "We think we can take them and leave them, even though we like them. We think we can see them on Channel 12."

Not so. Tallamy compares wildlife and biodiversity to the rivets holding together a plane in flight. Take out too many, and uh-oh. The plane - or the ecosystem - crashes. And then we start to lose all the "services" a well-functioning ecosystem provides, such as clean water and clean air.

Tallamy gives a quick rundown of species decline in our midst - all the insects and birds and mammals that are in trouble - and by now the audience is hushed, depressed. Me, too. But hang on. Better news to come.

Tallamy is a busy man these days. He has only himself - and the increasing popularity of his message - to blame.

Back when he began giving talks about the subject, people kept asking if he had anything they could read. He didn't. So he wrote a book, Bringing Nature Home. It was first published in 2007, and he figured that would be the end of the talks. There'd be no more need for him.

Instead, demand only increased.

He also figured he'd get some pushback from the nursery and lawn industries. Instead, they starting inviting him to talk, too. Now, he gives a hundred of these talks a year. Last week, he was headed to Mississippi for one.

Tallamy isn't blaming anyone for the sterility of our current landscapes. He acknowledges that many horticulturists aren't ecologists, they're artists, painting the planet. "Aesthetically, it works great. But ecologically, it's not supporting any food webs."

Ultimately, his message is hopeful and exciting. He maintains that we can have both the bugs and the beauty. Native plants can change everything, and change it quickly.

In his own home in southwestern Chester County, Tallamy and his wife, Cindy, have spent years replacing alien plants with natives and ripping out the invasives, like multiflora rose. They planted Virginia creeper to benefit a particular kind of moth. "This is how I play," he said.

An alternate leaf dogwood outside his bathroom attracts a litany of birds that he happily lists for the audience. A lot of people go to far-flung places like Costa Rica to look at a wide variety of birds, he said. "I just go to my bathroom."

In study after study, his students have compared natives to nonnative plants and found large differences in the number of species they support. In a study of ornamentals, his students found that native plants hosted 72 species of insects, and introduced ornamentals hosted only four.

For people worried about all those caterpillars and insects that are going to show up and potentially devour the landscape, Tallamy has reassuring words. Birds also will show up - that's part of the point, after all - and eat the insects. Tallamy said studies looking at damage have found that it is below a commonly accepted "aesthetic injury level" of 10 percent.

If not all plants are created equal, Tallamy warns, not even all natives are created equal. A native oak, for instance, supports 534 species of butterflies and moths, while a native walnut supports just 130. Asters support 112 species of butterflies and moths, while irises support just 17. (He has lists on his website,

But that's probably for people who are really getting into this. For most of us, Tallamy would like to see us simply chip away at our lawns, replacing them with native trees and shrubs. A little lawn is OK, but it should have a purpose, like ball-playing.

Tallamy proposes a new national park that he would call Homegrown National Park. It would be 20 million acres of household yards, reinvented to support biodiversity. It would trump a dozen or more "real" national parks in size and, more than likely, effect.

"We don't have to get the government involved," Tallamy told an audience now looking infinitely happier than when he was talking about biodiversity loss. "We can put these native plants in our yard and see conservation right before our eyes."

Ed Bonsell has seen it. He has been gradually transforming his Hatfield property of about an acre. Each year, he plants about 20 native trees and shrubs. It's more than a weekend project, but nothing outrageous. By now, he's rewarded with a full chorus of birdsong he wasn't hearing before.

If Tallamy's message is getting some traction, it's perhaps partly because it gives people a goal, turning their yard into something important. "Gardening with natives is no longer just a peripheral option favored by vegetarians and erstwhile hippies," he writes in his book. "It is an important part of a paradigm shift in our shaky relationship with the planet that sustains us - one that mainstream gardeners can no longer afford to ignore."

Later, I confessed to Tallamy about my hydrangeas. He gave me a dispensation. "That's OK to have things that remind you of your grandmother," he said. As long as that's not all I have.

It's not. Fortunately, I have a fair number of natives. I'm looking at my oaks and bee balm with new respect.

But this spring is going to be exciting. After hearing Tallamy's talk, I have big plans.

Contact Sandy Bauers at 215-854-5147, or on Twitter @sbauers. Read her blog, "GreenSpace," at