Through studies, books and talks, entomologist and ecologist Doug Tallamy has been spreading the word for years about the threats facing wildlife and the many reasons to practice ecological gardening. Every day he receives emails from gardeners who want to use the land they steward to make a difference, so for his latest book, he gathered the most frequently asked questions and his thoughtful, research-backed responses.
Doug holds both a master’s and a Ph.D. in entomology — the study of insects — and he’s a University of Delaware professor in the Department of Entomology and Wildlife Ecology. He has long studied the interactions between plants and insects, and the interactions between insects and the birds and other wildlife that eat them. His earlier books on the importance of conservation and native ecology include “Nature’s Best Hope,” “Bringing Nature Home,” and “The Nature of Oaks.” His latest is titled “How Can I Help?: Saving Nature with Your Yard.”
Entomologist, ecologist and conservationist Doug Tallamy has a new book out titled “How Can I Help?: Saving Nature with Your Yard.”
Photo Credit: Rob Cardillo
As a renowned expert on native gardening, Doug Tallamy receives A LOT of questions. Many questions have come up again and again, so he began to save the answers he had written.
“These are people that have already heard my talks, and they’ve read my other books, and they still have really good questions,” Doug explains. “So I said, this should be another book.”
Doug’s books — and “How Can I Help?” is no exception — are based on peer-reviewed studies that he and others have conducted. Anyone who cares about wildlife and wants to do better will want this book not only for themselves but also to share. In fact, I think this book should be mandatory reading.
“How Can I Help?” is 300-some pages, a third smaller than Doug had originally submitted to his publisher. He boiled it down to remove some similar questions and answers without losing any of the valuable lessons he has to offer.
Why Should I Care About the Food Web?
The importance of the food web not only to wildlife but also to humans is a topic that Doug says he has the most trouble getting across to people.
“It all goes back to this idea that we’re separate from nature,” he says. Some people think nature is nice, we like it, but we don’t need it.
But, oh, how wrong they are. A functional food web creates an ecosystem that we all rely on.
“Plants are capturing energy from the sun, and they’re turning it into food — the simple sugars and carbohydrates, which is the food that supports just about all the animals on the planet,” Doug explains. “If you don’t get that food to animals, you don’t have any animals. And if you don’t have any animals, you don’t have a functional ecosystem. And if you don’t have a functional ecosystem, you don’t have humans. That’s the connection. Ecosystems provide the life support that keeps us alive on this planet.”
It’s not adequate for ecosystem services to occur out in the wild.
“What’s happening in our parks and preserves is not enough,” Doug says. “We need functional ecosystems everywhere. And that means sharing our spaces with nature — our human-dominated spaces.”
The Importance of Supporting Caterpillars
If you have read Doug’s books before or listened to him on this podcast, you know he is an advocate for supporting caterpillars in home and commercial landscapes.
“The most important creature in terms of taking energy from the plant to other animals is caterpillars,” Doug says. “They’re transferring more energy to other animals than any other type of plant eater. So it’s a long way of saying if you make a landscape that doesn’t have enough caterpillars in it, you’re going to have a failed food web and eventually a failed ecosystem.”
A landscape without enough caterpillars for a bird to raise its offspring is a dead landscape, he says.
“If you have enough caterpillars, they will be able to breed. But that means you’ve got to have the plants that make those caterpillars, and most of them don’t make a lot of caterpillars.”
When humans make more conscious plant choices, their yards can become a buffet of caterpillars for birds and other wildlife.
An example Doug often cites is the Carolina chickadee. “It takes 6,000 to 9,000 caterpillars to get one clutch, and that’s a bird that’s a third of an ounce,” he points out, adding that even after the chicks leave the nest, their parents continue to feed them for another 21 days. “No one has counted that because they’re flying all around. But you’re talking about tens of thousands of caterpillars required to make one nest of a tiny bird,” he says.
A diversity of caterpillars is important in addition to the quantity, as Doug addresses in his book.
Even if you rarely see caterpillars on your native plants, that doesn’t mean they aren’t there. Birds are just better at finding them than you are. Birds are visual predators and can spot caterpillars we would overlook when staring right at them.
There is intense selection pressure on caterpillars to stay hidden, and they are really good at hiding from you, Doug says. “Many of them crawl off the leaves during the day, and they hide on the bark or the stem. Some of them actually crawl all the way off the plant, and they’re hiding in the grass on the ground. Then they’ll go back up at night. So nighttime is the best time to actually look for caterpillars.”
The easiest way to detect caterpillars is to look for caterpillar damage, like little holes or chewed up leaf margins. If your leaves haven’t been touched, then you really don’t have any caterpillars, and that’s a problem, Doug says.
A bluebird carries insects to feed its young.
Courtesy of Doug Tallamy
What’s the Definition of Invasive?
An invasive species is a non-native plant or animal that is causing harm. Though when Doug discusses invasives, he’s always discussing the plants.
“My definition of harm is they’re displacing the native plants that drive the food webs of our ecosystems,” he says. “So right away, they’re non-native, which means … they’re very poor at supporting our local insects.”
When invasives like autumn olive, multiflora rose, Oriental bittersweet and bush honeysuckle move in, they push out the native plants that do create caterpillars. Doug likes to call caterpillars “bird food.” When there are fewer caterpillars around, consequently, there are fewer birds.
“We have measured what happens in a typical invasion in hedgerows in Pennsylvania, Maryland and Delaware, and it’s a 96% reduction in caterpillar biomass,” Doug says.
“We’ve lost 3 billion breeding birds in this country in the last 50 years, and there are several reasons for that,” he adds. “But starving them is one of them. You know, there’s no bird that can breed in a habitat where there’s 96% fewer caterpillars.”
Deer Control Is Invasives Control
Invasive plants begin as introduced species, whether introduced to a new area intentionally as ornamental plants or unintentionally, hitching a ride with something else being transported along distance.
Some argue that introduced species dominating native plants is a matter of survival of the fittest and they deserve to be the winners. Doug rejects that notion.
“They’re actually not more fit at all,” he says. “They are simply plants that are here without their natural enemies. So they came over here without their diseases. They came over here without the insects that do eat them back home. And the primary reason — what’s really becoming more and more obvious every year — is our overabundance of deer. Our white-tailed deer do not eat these plants. They do eat the native plants. So that competitive balance is pushed totally against our natives.”
When you fence out deer, natives are quite competitive, Doug notes. Invasives aren’t super-plants. It’s just that the deer don’t like them.
When there is a major invasive species removal effort, the natives don’t come right back, he says. As soon as a native oak tree or native viburnum pops out of the ground, the deer eat it. The result is an empty landscape, and what comes back eventually are the plants that deer don’t like to eat — the invasives.
Deer don’t like to dine on invasive plants. They prefer native plants, which puts pressure on natives while giving invasive plants a competitive advantage.
How to Remove Invasives
To remove invasive plants, Doug likes to use a mattock, a pickax with a flat end known as an adze. When he was in Africa for a study, he saw that the mattock was the local tool of choice of road workers, and he was inspired.
Whacking invasives with a mattock is an herbicide-free way to control invasive plants. You can use a long-handle mattock or a short-handle mattock.
For bigger invasives, Doug recommends chopping them down then painting the stump with Garlon 4, an herbicide designed for woody plants, unlike Roundup, which is a foliar herbicide. Garlon 4 is active even when the temperature is below freezing, and it kills the roots so the plant does not regrow.
Another method is to cover a stump in a square of heavy black plastic secured with garden staples. Leave it for a year or two, and the lack of light will kill the stump after a year or two.
Cutting back an invasive plant repeatedly — once every two weeks — will eventually exhaust the energy that is in the root system. The trick is to stop it from photosynthesizing again by removing the foliage frequently, but you may be at this for a long time.
Controlling the Sale of Invasive Species
“In the state of Delaware, the sale of invasive species is banned,” Doug says. “… We did that by getting everybody in the same room. The nurserymen. The conservationist. Red and blue folks. Everybody was in the same room. And in the end, the final vote was 100% for banning it. And that included the nursery folks because they know they shouldn’t be selling these things.”
The honor system didn’t work because no businessmen want to see their customers go to another nursery where a plant they don’t offer is for sale. A statewide ban leveled the playing field.
How To Dispose of Invasive Plants
Autumn olive, multiflora rose, Oriental bittersweet and bush honeysuckle, once cut or pulled, will break down relatively quickly.
“We just pile up the bodies,” Doug says. Then in a year and a half or so, it’s settled right down.
But something like Japanese knotweed is a different story.
“You certainly don’t want to take that out and then put it in the trash or something because a root particle the size of your pinky nail will start a new plant,” Doug says.
You can make a pile, put them under a plastic sheet, and solarize them. “The sun comes down and cooks them,” Doug says.
Berry-Producing Invasive Plants and the Birds That Eat Their Berries
Some non-native plants attract birds, but that is not necessarily a good thing.
“One of the major reasons these plants are invasive is that they make berries, and the birds do come and eat the berries and fly away and poop them out,” Doug notes. “That’s how they move around.”
And that’s not the only problem.
Susan Smith Pagano, an associate professor of biology at Rochester Institute for Technology, has been studying the quality of the berries made by these invasive plants.
“She has found this very clear pattern,” Doug says. “The berry-makers from Asia make berries that are very high in sugar. The trouble is they make them in the fall. So birds are eating plants or berries that are high in sugar in the fall when they need berries that are high in fat.
“So the best berries for our birds during the fall when they’re migrating or getting ready to overwinter would be Virginia creeper, native viburnums, wax myrtle, poison ivy. Those are making berries that are really high in fat, like up to 50%. Whereas, multiflora rose and autumn olive and those guys, it’s around 1% fat. So the rest of it is sugar.”
Birds eat the berries of invasive plants because they may be the only berries available to them. Susan found that when given the choice of native berries and non-native berries, they choose the natives.
Poison ivy and Virginia creeper, both native plants, produce berries that are high in fat, which is just what birds need to prepare for winter.
How to Prioritize Which Invasive Plants to Remove First
When removing invasive plants, Doug prioritizes those that are casting the most shade and excluding the greatest number of other plants. But he also prioritizes those that are the easiest to remove. For example, removing Japanese stiltgrass is tedious and time consuming, but removing bush honeysuckle is a breeze that can quickly open up a large space.
Why Doug Tallamy Doesn’t Use Mosquito Fogging Companies
Doug does not fog his property for mosquitoes, and he doesn’t hire anyone else to do it for him either.
“They will tell you that it is a natural organic product that only kills mosquitoes, and if that were true, I’d hire ’em,” he says.
The ingredients the organic fog companies are selling are pyrethroids, the same series of compounds that are made by chrysanthemums as insecticides.
“It’s industrial-strength pyrethroids. You can say, okay, this is a natural product. But cyanide is a natural product. And ricin is a natural product. So, you know, being natural and organic sounds warm and fuzzy, but not necessarily,” Doug says.
He added that “only kills mosquitoes” is blatant false advertising. “And I don’t know how they get away with that. It kills all the insects it comes in contact with including our poor monarchs, including our pollinators that we’re trying to save.”
He advises controlling mosquitoes in the larval stage, not the adult stage. Get a bucket, fill it with water and put in a handful of organic matter (straw, hay or dead leaves) and put it out in the sun for a few days.
“It builds up the populations of diatoms and algae, and that is what mosquito larvae eat. So that becomes an irresistible brew to any female mosquito in your yard. She’ll lay her eggs in that bucket. Then you go to the hardware store and you buy a sheet of mosquito dunks. $12 for a season’s worth of control. That’s Bacillus thuringiensis, which is a natural bacterium that only kills aquatic diptera. And the only aquatic diptera in your bucket is a mosquito larva. So it’s cheap, and it’s targeted. You’re not killing the world.”
Mosquito Dunks added to standing water control mosquito larvae. They won’t harm beneficial insects.
Propagate Milkweed Easily
Starting milkweed can be difficult because it requires stratification. But Doug says there is an easier way to propagate milkweed. But you need access to an existing milkweed patch.
Many species of milkweed spread by stolons, or runners. If you dig up a stolon and bury it where you want a new plant, you’ll get a new one really quickly.
“I discovered this in my own vegetable garden years ago where some milkweed started to come up and I didn’t want it,” Doug recalls. “So I rototilled. So I turned three milkweed plants into about a hundred by chopping up the roots, and then they all came up.”
These new plants will be bigger than new plants that sprouted from seeds, and that will make them less susceptible to deer browsing.
Asclepias syriaca, or common milkweed, spreads via stolons, or runners. (Photo: Amy Prentice)
Light Pollution and Global Insect Decline
“We have light pollution everywhere. We also have global insect decline,” Doug notes. “And it turns out that light pollution is one of the major causes of global insect decline. Because an insect’s attracted to light, particularly those moths that are creating the caterpillars that run our food web.
“Very rarely do they actually leave that light alive. They can circle it to exhaustion. They can bang into it and get fried. They’ll sit on the edge of the building where the light is, and in the morning, the birds come and pick them off. There are predators. You can see toads sitting underneath the lamp and picking off the insects that come and get tired and fall down to the ground. Other insect predators come. So a lot of things are killing insects.
“Plus it has diverted the insect from what it’s supposed to be doing. It’s supposed to be looking for a mate and a host plant — not sitting next to a light all night long.”
Doug recommends turning off outdoor lights or using security lights that only turn on when they detect motion. Choose a yellow LED, which attracts far fewer insects than a white incandescent bulb while using far less energy.
“It’s something that a simple trip to the hardware store can solve,” he says. “And if everybody did it, it really would make a huge difference.”
The Most Important Thing to Remember When Planting a Pollinator Garden
The most important thing to remember when planting a pollinator garden is to meet the needs of the specialist pollinators, according to Doug.
“We’ve got between 3,600 and 4,000 species of native bees in this country, and a third of them that we know of can only reproduce in the pollen of particular plants. Those are the pollen specialists. The generalists can use pollen from lots of plants. So honeybees are generalists. Many of the bumblebees are generalists. So if you plant with the specialists in mind, the generalist can also use those plants. So you’re covering all your bases.”
Plants like goldenrod and perennial sunflowers and fall-blooming asters are all really good at supporting specialist bees, he says. Those three genera can support 44 species of bees that won’t have a reason to visit your yard otherwise.
A chickadee with a caterpillar in its beak. Courtesy of Doug Tallamy
Plant Keystone Plants
“Not all natives are created equal,” Doug says.
Researchers like Doug have found by looking at host records of caterpillars throughout the country that just 14% of our native plants are supporting 90% of the caterpillars.
“You’ve gotta include that 14%, and that’s what we call the keystone plants because they’re — I always say — they’re the two-by-fours that are holding up our ecological house,” he says. “Those are the workhorses supplying all those caterpillars that drive the food web, and oaks lead the list in 84% of the counties in which they occur. But native willows are very high, native cherries are very high. Birches are high. It depends on where you live. As you go farther north and you get beyond the range of oaks, then willows take over.”
The Best Thing We Can Do to Support Our Environment
The best thing one can do to support the environment is to vote, Doug says.
“Who we vote for is really, really important. Don’t vote for somebody who doesn’t believe in science. Don’t vote for somebody who denies that the sky is blue. Yes, there is still a Flat Earth Society, but I’m not going to vote for that person. Because that person is going to set policy that will determine the quality of your life and your kid’s life. And it can be really hard to undo some of the things that are happening today.”
Closing Words
Property owners have a responsibility to take care of the pieces of the earth they own, Doug says.
His book is full of ways to do that, those mentioned above and much more.
“These are all simple things that one person can do to totally revitalize how well their property is functioning,” Doug says. “That’ll improve ecosystem function in your entire neighborhood. But it also empowers you. Don’t think about the entire planet’s problems because you get depressed if you do that. Just think about the piece of the earth that you can influence. Because that makes it manageable. You can do it. You can see the results and feel like you’re part of the solution instead of part of the problem.”
“How Can I Help?” includes Doug Tallamy’s answers to FAQs on conservation and gardening for wildlife.
I hope you enjoyed my conversation with Doug Tallamy on his book “How Can I Help?” If you haven’t listened yet, you can do so now by scrolling to the top of the page and clicking the Play icon in the green bar under the page title.
What have you done to help wildlife in your yard? Let us know in the comments below.
Links & Resources
Some product links in this guide are affiliate links. See full disclosure below.
Episode 012: Beneficial Garden Insects – Bringing Nature Home with Doug Tallamy
Episode 050: Organic Pest Control: Beneficial Insects and Beyond
Episode 067: Predatory Beneficial Insects: Feared Foes of Garden Pests, Pt. 1
Episode 071: Gardening for Wildlife: How-to Create an Inviting Habitat, with NWF’s David Mizijewski
Episode 076: How to Create a Bird-friendly Yard
Episode 077: The Beauty and Importance of Native Plants: The Ethos of Mt. Cuba Center
Episode 133: Native Plant Design in a Post-Wild World, with Thomas Rainer
Episode 134: Bird Population Decline and What Gardeners Can Do to Help
Episode 142: Why Our Plant Choices Matter: Nature’s Best Hope, with Doug Tallamy
Episode 152: The Native Plant Trust: Why Plant Choices Matter
Episode 197: The Many Benefits of Building a Naturalistic Garden, with Kelly Norris
Episode 206: Our Most Essential Trees: The Nature of Oaks, with Doug Tallamy
Episode 237: Ecological Gardening: Creating Beauty & Biodiversity
Episode 258: Averting the Insect Apocalypse, with Dave Goulson
Episode 331: The Ecological Garden Blueprint: 10 Essential Steps That Matter Most
Episode 413: Easy Actions Anyone Can Take To Support Wildlife
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joegardener Online Gardening Academy Beginning Gardener Fundamentals: Essential principles to know to create a thriving garden.
joegardener Online Gardening Academy Growing Epic Tomatoes: Learn how to grow epic tomatoes with Joe Lamp’l and Craig LeHoullier.
joegardener Online Gardening Academy Master Pests, Diseases & Weeds: Learn the proactive steps to take to manage pests, diseases and weeds for a more successful garden with a lot less frustration. Just $47 for lifetime access!
joegardener Online Gardening Academy Perfect Soil Recipe Master Class: Learn how to create the perfect soil environment for thriving plants.
GGW Episode 509: Greening of Suburbia
GGW Episode 1008: Bringing Nature Home
“How Can I Help?: Saving Nature with Your Yard” by Doug Tallamy
“The Nature of Oaks: The Rich Ecology of Our Most Essential Native Trees” by Doug Tallamy
“Nature’s Best Hope: A New Approach to Conservation That Starts in Your Yard” by Doug Tallamy
“Bringing Nature Home: How You Can Sustain Wildlife with Native Plants” by Doug Tallamy
Cornell Lab of Ornithology Study: Nearly 3 Billion Birds Gone
“The Insect Apocalypse Is Here” | The New York Times
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Disclosure: Some product links in this guide are affiliate links, which means we get a commission if you make a purchase. However, none of the prices of these resources have been increased to compensate us, and compensation is not an influencing factor on their inclusion here. The selection of all items featured in this post and podcast was based solely on merit and in no way influenced by any affiliate or financial incentive, or contractual relationship. At the time of this writing, Joe Lamp’l has professional relationships with the following companies who may have products included in this post and podcast: Milorganite, Soil3, Territorial Seed Company, Proven Winners ColorChoice, and Dramm. These companies are either Brand Partners of joegardener.com and/or advertise on our website. However, we receive no additional compensation from the sales or promotion of their product through this guide. The inclusion of any products mentioned within this post is entirely independent and exclusive of any relationship.
