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You're listening SCIENCE FRIDAY from NPR News. I'm Ira Flatow.

Have you been catching those lawn weed and feed commercials that you see everywhere now and the American dream of that perfect lawn? No shaggy borders, no stray dandelions and absolutely no brown spots. And I say it's American tradition that goes back to our founding fathers. You can look at some of the giant lawns out there in Monticello or where the President Washington lived and who could keep up a fancy lawn like that? They could have abundance of slave labor to maintain the grounds of your estates if you were a colonialist I'm sure. But one of the recent estimates says today grass carpets of up to - 40 million acres cover the United States.

We have 40 million acres of grass. That's an area of the size of Missouri. And what if I tell you that you don't have to have a lawn like that? You don't have to go out there and mow and do all kinds of stuff. You can ditch your lawn or at least part of it to make room for a few native shrubs and flowers and it's not just to avoid spraying all the pesticides or polluting the lakes and the oceans with that lawn food run off or to quit using that rackety old gas mower. A better reason is because your local bugs and birds are going to love it and you can turn your piece of the rock into a wildlife sanctuary. How do you do that? Well, that's what we're going to talk to, tell you about this hour.

Our number 1800-989-8255, 1800-989-talk. You can Tweet us. Our Twitter @ sign followed by SciFri, S-C-I-F-R-I. We're also on Second Life and you can reach us in a whole bunch of different ways. Here to talk about how to do that -"Bringing Nature Home" is the name of the book - how you can sustain wildlife with native plants is Doug Tallamy. He is the author of "Bringing Nature Home." As I say how you can sustain wildlife with native plants. He is also professor and chair of Entomology and Wildlife Ecology at the University of Delaware in New York. Welcome to SCIENCE FRIDAY.

Dr. DOUG TALLAMY (Professor of Entomology and Wildlife Ecology, University of Delaware): Thank you, Ira.

FLATOW: Why did you write this book?

Dr. TALLAMY: Well, that's a good question. I actually have been doing research that is demonstrating that the native plants in our landscapes are disappearing because of the way we landscape. And of course they are basis of the food web, so everything that depends on them are disappearing as well. And I started giving talks about this to - I guess because people were asking me to give talks.

FLATOW: Yeah.

Dr. TALLAMY: And people said are there something to read about it? And I said well, no, not really. So, after a year of that, I decided I would actually write a pamphlet. So the book turned into the - the pamphlet turned into the book and that's what we have.

FLATOW: And so you're proposing that we don't - not give up your whole lawn if you don't want it to but you can give up a good part of it and turn it into a flower bed, woody area, things like that.

Dr. TALLAMY: Right. This isn't really a war on lawns. It's an effort to save the biodiversity of the country. That is the main problem. We have as many as 33,000 species of plants and animals in this country that are in serious trouble and that their numbers are now so low they are no participating in their ecosystems. So, they are not performing their jobs and we can call them functionally extinct, even if we can still find a few members. Well, you know that's an extinction crisis and we've got to bring these species back or at least curb their loss. And the way we need to do that is to turn the spaces that we humans have taken for our own use into areas that can - we can share with other species.

Most people don't realize the size of the human footprint not just on the planet but right here in the U.S.,. In terms of usable land and good space, we've taken just about all of it. We got about 41 percent of the country in agriculture and about 54 percent in cities and suburbs and this matrix of little teeny habitat squares that remain. There is really only about 5 percent of the country that's relatively pristine and that's not nearly enough to preserve the biodiversity that we need to maintain our ecosystem.

FLATOW: Now what - and you say in your book, people - the first thing they ask if - they say: Hey, you know, I want to get in on this. What should I plant?

Dr. TALLAMY: Right.

FLATOW: What should I plant? What kinds of species will preserve - what kinds of plants will preserve what kinds of species?

Dr. TALLAMY: Well, there are a couple of things you've got to remember. We're not trying to create little museums or little collections of plants from all over the country and say we've got a native garden. We're trying to recreate food webs that used to be in your area. So, we are focusing on plants that had an evolutionary relationship with the plants and animals that used to be where you are, wherever that is. So, what you plant depends on the part of the country that you come from. And the second thing that I'm trying to tell people is that all plants are not created equal, so it's not simply a matter of focusing on native plants. But there are some native plants that are far better at supporting wildlife than other native plants.

FLATOW: For example.

Dr. TALLAMY: For example, oak trees in the East are number one. We've done a study that looks at the number of caterpillar species, the number of Lepidoptera moths and butterflies that can be supported by every woody plant or every genus of plant in the mid-Atlantic states - that's 1385 genera that we've look at. And out of that - in that study, we found that oaks are number one. They can support 534 species of caterpillars. And, you now, every single one is ranked right down to zero. So, if you are trying to pick - maybe you have space for, you know, just one tree in your yard. I would pick an oak over something like a tulip tree that only supports 21 species of caterpillars.

Now why am I talking about caterpillars? First of all, we know more about what caterpillars eat than any other insect group. So it's a good index of the biodiversity that could be supported by plants. And also, we know that birds, in particular, but many other things eat caterpillars. Insects are an essential part of every terrestrial food web and therefore any plant that makes a lot of insects is going to be really productive in supporting wildlife.

FLATOW: So, by - just by growing some oak trees in your native - where they would grow, you could just bring - you could support all this whole food web that's going on.

Dr. TALLAMY: You could go a long way towards it. Now, I would never recommend that you only…

FLATOW: Yeah.

Dr. TALLAMY: …plant oaks. We don't want a monoculture of anything. But they are number one and if you - birders know that if you are going to look at migrating birds, the best place to do that is to stare into the canopy of oak trees. I just noticed that a few weeks ago in Maine when the warblers are moving through and I was staying with some folks and they had a variety of trees around, but the warblers were only in the oaks.

FLATOW: Yeah.

Dr. TALLAMY: Because that's where the food is.

FLATOW: Yeah.

Dr. TALLAMY: They're going to go where it's easiest eating.

FLATOW: In your book, you talk about the common reed, the fragmities…

Dr. TALLAMY: Right.

FLATOW: …in Europe where it is native and you contrast that to the situation in America. And that's how - that's the one of these fluffy plants we see all the time in swamps and marshes, right?

Dr. TALLAMY: That's right.

FLATOW: And - what's the difference between it being in Europe and it growing here?

Dr. TALLAMY: Well, it's - the plant you see in this country is a genotype from Europe. So, people argue about whether it's the same species or not. So we don't - it doesn't matter what we're going to call it. But the genotype that you see growing here is the one from Europe. It has been here for about 400 years. And people often ask, if a plant is here long enough, if it can become a native?

FLATOW: Right.

Dr. TALLAMY: Well, the best way to determine whether it has become a native is to see whether it has reached its full potential in supporting life. So, we can go to Europe. We could see how many insects does fragmities support in Europe -and I think it's a 156, something like that, species of insects in Europe. Over a year, after being here for 400 years, it only supports five. So will it reach its full potential? Probably eventually, but, you know, are we talking 10,000 years or 100,000 years longer, we are not sure. So the bottom line is that plants don't act like natives very quickly.

And that the insects that require these plants and all of the animals that require those insects are going to be in trouble until they do adjust. So, there's real cost to converting our landscapes to different gardens and landscapes that are filled with plants that evolved some place else.

FLATOW: Yeah, because as you say, the insects won't eat them.

Dr. TALLAMY: The insects won't eat them. The birds will have nothing to eat. You know, 96 percent of our terrestrial birds, rear their young on insects. So people feed birds all winter long because they're considered about the birds.

FLATOW: Right.

Dr. TALLAMY: But then during the summer when the birds are trying to reproduce, we unwittingly starve them by the way we landscape, so…

FLATOW: Why can't insects eat these non-native plants?

Dr. TALLAMY: All right, that's a good question. Insects, and we're talking largely about the ones that eat the leaves, the folivores, can't eat most plants because plants don't want to be eaten. Plants protect themselves chemically. You know, of course, plants are gathering energy from the sun. They convert it into the food that drives life on earth, but plants want to use that food for themselves, for their own grown and reproduction.

So they pack these nasty chemicals into their leaves, and most herbivores cannot eat most plants because they taste bad. But we do know that insects eat plants. So how do they do it? They do it by specializing on a particular group of plant compounds, particularly a group of secondary metabolic compounds that are used as defenses.

And I always use the monarch as a perfect example of this. The monarch butterfly, of course, is a specialist on milkweed, but milkweed's a toxic plant. It's filled with cardiac glycosides, which if we eat them would give us a heart attack, but the monarch has specialized and developed the particular enzymes and physiological adaptations that are required to break down and detoxify and store and excrete those cardiac glycosides.

So that's a specialized relationship that works very well for the monarch, as long as there's milkweed around. The problem with specialization is that if we go along the roadside and mow down the milkweed, the monarch cannot crawl off and start to eat asters or dandelions or anything else because they didn't specialize on those.

So there's a - when an insect specializes on one class of compounds, which is carried by one group of plants, it loses the ability to eat other groups of plants.

FLATOW: And it's going to take forever it to…

Dr. TALLAMY: Well, in ecological terms, yes. So we can't ask insects to all of a sudden adapt and start to eat plants from China. They can't do it.

FLATOW: And so if we don't plant the native plants, we're not going to get the insects we need to feed the birds and increase the biodiversity of the area.

Dr. TALLAMY: In general. Now we're talking about 90 percent of our insect herbivores are specialists, just like the monarch, but that leaves 10 percent that are generalists that have wider host ranges, and I've actually just finished a study at the University of Delaware looking at how well these generalists are able to use plants that they did not co-evolve with, and I looked at things like the white martussic(ph) moth, which is the most generalized insect in the mid-Atlantic state, and the bag worm, which is the second-most-generalized insects, and they have dozens and dozens of plant genera that they can eat. But when I try to rear them on plants that evolved in China, in almost all cases they died in the first - or right after they were hatched out of their egg.

And it was very few exceptions. The bag worm, for example, did survive on Norway maple, but that was the only alien that it survived on.

FLATOW: All right, Doug. I'm going to have to interrupt, and we'll go to a break and come back and talk lots more, okay? Stay with us. Talking with Doug Tallamy, author of "Bringing Nature Home," how you can sustain wildlife with native plants. Our number, 1-800-989-8255. Stay with us; we'll be right back.

(Soundbite of music)

FLATOW: I'm Ira Flatow. This is SCIENCE FRIDAY from NPR News.

(Soundbite of music)

FLATOW: You're listening to SCIENCE FRIDAY from NPR News. I'm Ira Flatow, talking with Douglas W. Tallamy, author of "Bringing Nature Home," how you can sustain wildlife with native plants (unintelligible) grow native plants in your backyard or you want to give up a little bit of your grass to mow and go to native plants there, you will attract the native insects, and that'll attract the birds and make the caterpillars happen, and you can that all happening right in your backyard.

Let's go to the phones. 1-800-989-8255. Let's go to Matty(ph) in Hill City. Where's Hill City, Matty?

MATTY (Caller): It's in South Dakota.

FLATOW: Ah.

MATTY: Yeah.

FLATOW: Go ahead.

MATTY: And I live with a national forest on two-and-a-half sides of me, so I've out of necessity every time I try to plant something that's not already growing here, either the deer come and eat it or the rabbits or the chipmunks, or I've got mountain lion and bobcats that would eat my cat if I let my cat stay outside.

So I just have reverted to letting it be totally natural, but then I have the situation that my uncle and other people tease me, and they say, oh man, I see your lawn is knee-high again. So do you have any way of explaining to them without lecturing them?

FLATOW: Doug, any suggestion?

Dr. TALLAMY: Yeah, this is a big problem. It's not just your uncle that is a problem, but civic associations across the country have very strict rules about exactly how our landscape should look, and of course the grass has to be mowed within an inch of the ground, and in the fall when the leaves fall you're not allowed to have any leaves on your ground. You've got to rake them all up and throw them away.

In other words, we've got to sterilize our landscapes. Otherwise it implies we, you know, we're not taking care of things and we're low-status, and it's not good.

So what I'm proposing is, first of all, that if you have lawn, that you take care of the lawn that you do have. It's not a matter of simply stopping mowing and abandoning the landscape. I'm suggesting that we reduce the area that's in lawn with an organized landscape design that is going to feature largely native plants, particularly largely woody native plants, because they will support the most animal diversity.

But they will be in flowerbeds and be part of a traditional design that is simply going to feature less lawn, and…

FLATOW: Give us an idea. If you're not going to start out with a big oak tree because, you know, it takes little acorn and they take a while to grow, what would you plant there if you're starting off and you want to change some of your landscaping?

Dr. TALLAMY: Well, first of all, oaks don't grow as slow as people think. I started some from acorns in my yard when we moved in eight years ago, and they're now 12, 15 feet tall. So in the meantime we can call them oak bushes, and while we have oak bushes, they're being very productive.

They're producing polyphemus moth larvae, and they're feeding the birds, and they're doing their job that I want them to do, even though they're not 300 years old. So I don't want to discourage people from large trees just because it takes them a while to get there, because they actually get there a lot faster than we think.

But under any trees that we have, we want to - what we want to do is recreate the layers of a typical forest. So you've got canopy, you've got sub-canopy, you've got understory trees like dogwoods, like shadbush, almalanker(ph), and then you've got the shrub layer, your blueberries and your native azaleas and viburnums and witch hazels and all of those plants that are part of a healthy understory.

And if you plant densely in these areas around your house, there'll be less maintenance because you won't have to weed. You know, we have weeds when we feature mulch in our gardens, where we have very few plants and large spaces of mulch, and then we've got to weed it all the time. But if you plant densely, the way it would occur in nature, and then you have these organized grass paths in front of those places, it appears neat, and it's very productive, and civic associations don't get upset about that.

FLATOW: Okay, Matty? Thanks for calling.

MATTY: Yeah, thank you.

FLATOW: (Unintelligible). What about - I'm sure a lot of people are saying, you know, what I don't want my plants to be is food for insects.

Dr. TALLAMY: Right.

(Soundbite of laughter)

FLATOW: You know? (Unintelligible) bring those caterpillars onto my plants. They're going to eat them up.

Dr. TALLAMY: Well, I understand that, but many of those same people do want birds in their yard. So what I'm really asking people to do is to build a balanced community. You know, in a healthy forest it is not defoliated with all the native insects, yet there are thousands of native insects there.

So what will happen, if you put a diversity of native plants in your yard, is that they will attract a diversity of native insect herbivores, but they in turn will attract a diversity of natural enemies that will keep those herbivores in check. You will have insect predators, you'll have insect parasitoids, and you will have those birds.

For example, a pair of bluebirds, when they're feeding their young, bring back to the next up to 300 caterpillars per day. So if you attract these other creatures, even though you will have some insects there, they're going to get eaten very quickly, so that they rarely get large enough to cause problems.

And we're actually measuring damage levels on properties that are landscaped largely with natives versus ones that are traditionally landscaped. And this is a young study. We've only done it for one summer at this point, but there's no difference in the damage level between these properties.

FLATOW: Let's go to Kenny in Louisville. Hi, Kenny.

KENNY (Caller): Hey, how you doing?

FLATOW: Hi there.

KENNY: Hey, what I learned was where I live - and actually I'm in southern Indiana, I just figured everybody knew where Louisville was, I'm across the bridge. But I used to buy a lot of perennials from the store, which obviously gets expensive, a lot of care needed to separate them constantly and so forth. But I found where I moved to, I've got a lot of just natural perennials, you know, just wildflowers, etc., all different types of daisies and ferns and etc., etc., vines blooming flowers, all kinds of things.

So I let them kind of go on their own, and I dig them up, move them where I want them and let them be.

FLATOW: What kinds are we talking about?

KENNY: Well, I wish I could say I was experienced enough to give you the names of them all.

FLATOW: They look pretty.

KENNY: Yeah, they're gorgeous. I mean, I could point them out in a book, but I've not yet looked them up because I work too much.

FLATOW: They bring butterflies and hummingbirds and things like that?

KENNY: Unbelievable amounts.

FLATOW: Yeah, I'm still…

KENNY: We've got also - I was going to say about grass, if you take good care of your grass for a period of time, get it in good shape and then let it grow, where it gets to 12 to 16 inches tall, it looks gorgeous because, you know, the top, you get the seeding area, and when the wind blows, you get to watch the grass just blow back and forth. It doesn't look like an unkempt lawn.

FLATOW: Quite interesting. Thanks, Kenny, for those suggestions.

KENNY: All right, thanks.

FLATOW: Good luck. Doug, what do you think?

Dr. TALLAMY: What do I think?

FLATOW: Yeah, I mean, getting the native - how do you find native perennials?

Dr. TALLAMY: Oh, it's easier and easier to find native perennials and native woody plants. There are more and more specialist nurseries that are focusing on those. You know, you Google native plants in your area and these things will pop up.

But this is a consumer-driven business. If you go to your nursery and you say I would like to buy this plant and they don't carry it, and if you say I'm not going to buy another one, I'm going to buy this one, they'll get it for you. They want to sell you plants that you're going to buy.

Right now we're kind of at a transition, where nurseries are afraid to carry too many natives because they're convinced that nobody will buy them, but if the public responds and said, look, we want to put some natives into the landscape, believe me, these people will start to carry them because they want to have your business.

FLATOW: 1-800-989-8255 is our number. (Unintelligible) Twitter to says where start, start digging up my grass? Don't mow? What's the first thing you should do?

Dr. TALLAMY: You know, it's funny. I've been going around the country giving talks, and people say, oh, I'm going to run home and rip out all my lawn, and that's probably not what you ought to do.

First you want to start with a plan, and I would suggest that you just pick at it. Start at a corner and work on an area until you're happy with it, but if you rip out your entire yard, then you're faced with a mammoth job, and usually not - you don't have the resources to do it all at once.

FLATOW: Right.

Dr. TALLAMY: So the first thing to do is to plan carefully. Again, I would start with the woody plants because they're more effective, and you can add them as you can afford them or simply wait for some of the plants in your yard to die, some of the non-native ones, and then replace them with natives. So do it by attrition.

But it can become a hobby. It can become a lifetime goal where over time you're going to increase the percentage of natives in your yard, but I'm a little leery about people that are going to go home and do it all right away because I know how much work it is.

FLATOW: A lot of people like rosebushes. Are there native rosebushes?

Dr. TALLAMY: Oh yes. There's three or four species of native roses.

FLATOW: Yeah, and you can just go - so you say go out and ask for that when you go to the nursery.

Dr. TALLAMY: Right.

FLATOW: Say I don't want this fancy hybrid from England somewhere. I want the native one.

Dr. TALLAMY: Yes.

FLATOW: Let me see if I can get a quick…

Dr. TALLAMY: You have specify, and unfortunately not all nurseries are going to be - well, not all nursery workers understand the difference between native and non-native. They say, well, here's a good native, and a lot of people think that if it's growing wildly, that it's a native, but that's simply an escapee.

As a matter of fact, 85 percent of the woody invasive plants that we have in this country have escaped from our gardens. So just because it's growing out in nature doesn't mean that it's native to the U.S.

FLATOW: Let me see if I can get a quick call in here before we have to say goodbye. Let's go to Elizabeth in Richmond, Virginia. Hi, Elizabeth.

ELIZABETH (Caller): Hello. Yes, I'm calling from probably the oldest neighborhood in Richmond. It's a downtown neighborhood with brick sidewalks and giant trees, a wonderful canopy, and when we first came here almost 30 years ago, we planted an ornamental crab, which was gorgeous. Everybody loved to stand and look at this beautiful tree. And all of a sudden, we realized it was loaded with these bags of worms that, you know, start out small and then hundreds and hundreds of them would drop to the ground and crawl around the corner to our giant oak tree.

And so, eventually after trying years after - year after year to kill them, we just ended up cutting the tree down. At the same time, the city was planting crabapple all over the place, and every tree in the parking lots had these worms in them.

We saw them as a pest. And when we got rid of the tree, it more or less cut down on the problem. The trees are much, much healthier looking now, which is why I'm really a little bit surprised about how important it is to have the worms.

But the other day, we realized that the woodpecker was making sounds of getting ready to nest. And within a day or two, my husband said he heard a scuffle down on the sidewalk, and we went out and there were bird feathers. And we've had a hawk flying around through the canopy or over the canopy and a falcon flying through the canopy, and we think that one of those birds got that woodpecker.

But my real question is what should we have done when these worms, these bagworms were just ruining the tree, the ornamental trees?

FLATOW: Is that caterpillar worms that you see in the…

ELIZABETH: I think that's - I mean, they were these furry things…

FLATOW: Yeah.

ELIZABETH: …that, you know…

Dr. TALLAMY: Was this in the springtime?

ELIZABETH: Probably. You know, the tree had flowered, the leaves were just incredible.

FLATOW: Are these gypsy moths, probably?

Dr. TALLAMY: No, it's the tent caterpillar.

FLATOW: Tent caterpillars.

Dr. TALLAMY: And…

ELIZABETH: And what do they turn into? Because I never could figure - we never saw them at that point. We never knew what they were.

Dr. TALLAMY: Well, they turn into a little brown moth that flies around at night and provides great food for bats and other nocturnal creatures. But the tent caterpillar is a problem because they do - they reach these explosive population levels very easily, and they can outstrip their predators.

So, in terms of convincing people to try to encourage nature in their yards, the tent caterpillar is one of the biggest problems I have because they are so apparent and they can reach these outbreak proportions so easily.

And of course, in suburbia, in most cases, there aren't nearly enough predators around to keep them in control. But their natural population mode of action is to be what we call an eruptive species. So they usually…

FLATOW: Yeah.

Dr. TALLAMY: …explode for two or three years and then they're gone for two or three years, and they explode for two or three years. There are very few species that do that, but that is one of them. And they make those ugly tents that nobody likes.

FLATOW: Yeah.

Dr. TALLAMY: The easiest thing is to recognize what the egg nest looks like. It looks like a little piece of Styrofoam that wraps around the twigs. And they're - they have one generation a year, and those eggs are there all summer long and all winter long. And they're easy to find and just scrape off so that you don't have to be…

FLATOW: Right.

Dr. TALLAMY: …cutting your trees down to take care of it.

FLATOW: Doug, thank you very much for taking time to be with us.

Dr. TALLAMY: You're quite welcome.

FLATOW: Doug Tallamy, he's author of "Bringing Nature Home: How You Can Sustain Wildlife with Native Plants."

I'm Ira Flatow. This is SCIENCE FRIDAY from NPR News.

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