The Four Ecologically Crucial Things You Should Do in Your Garden

 

"The ecologist Douglas Tallamy says your landscape can help manage the watershed, support pollinators, bolster a viable food web, and sequester carbon.

Each time I’m asked a question about some aspect of ecological horticulture, I hear another question triggered in my head:

What would Doug do?

My answer-formulating thought process starts by pondering that.

“Doug” is Douglas W. Tallamy, the entomologist and University of Delaware professor who is co-founder of Homegrown National Park, an educational nonprofit. Perhaps no other contemporary figure has done more to introduce gardeners to the intimate connections between plants and animals imperiled by the biodiversity crisis, and propose actions we can take. Dr. Tallamy’s core exhortation, starting with “Bringing Nature Home,” his 2007 breakthrough book:

Add native plants, and remove invasive ones.

He has also probably answered more ecology and native plant questions than anyone else, and his latest book, “How Can I Help? Saving Nature with Your Yard,” tackles 499 of them.

Dr. Tallamy distills essential takeaways in topics as big as evolution and food webs, alongside targeted, can-do answers, such as reducing hazard to beneficial insects from our human obsession with artificial light at night by switching to yellow lightbulbs and motion detectors, please.

Or what would Doug do about the peril of mosquito-fogging treatments? Skip them. Even fog solutions formulated from natural materials such as pyrethrin aren’t mosquito-specific, he explains, indiscriminately killing monarchs and other butterflies, pollinators, fireflies and more.

I recently asked him some other frequent questions; our conversation was edited for length and clarity.

Making room for natives is foundational to ecological horticulture. People with established gardens of nonnative ornamentals ask, “How much of it do I have to give back? How many hostas can I keep?”

There’s really only one study, and that’s what my grad student Desirée L. Narango did, looking at the percentage of native versus nonnative woody plants needed to support a population of chickadees. The figure she came up with was 70 percent native, which means 30 percent nonnative. That is that area of compromise.

Now, you can’t compromise with invasives. They are ecological tumors, so even one is not good. But there’s plenty of ornamentals that are not invasive.

But that’s one study, with one bird and one place. We should not over-extrapolate that.

What I think about is what the ecological responsibilities of every landscape are. There are four of them:

Every landscape needs to manage the watershed in which it lies. Every landscape needs to support pollinators. Every landscape needs to support a viable food web. And every landscape needs to sequester carbon.

So you’ve got your ornamental landscape already established; it’s already doing some of those things. Which ones can you do better each year? Just pick at it. Maybe I can add an oak tree. Maybe I can add a little patch of goldenrod that’s not there now.

You don’t have to think about redesigning the entire landscape. Just say, “Can I improve on any one of those four goals incrementally over time?” And that way you can feel good about doing it and it gets done, but it’s not overwhelming.

Lawn furthers none of these goals, does it?

Lawn doesn’t do any of them, and that’s the issue. It’s not just neutral; if you have a good lawn the way you’re supposed to, it destroys the watershed, or at least it degrades it. It’s not supporting any pollinators. It’s not supporting a food web. And it’s the worst plant choice for sequestering carbon.

We can do better.

But it has important ornamental value in terms of a cue for care: It shows your neighbors that you know what the status symbol is — that you’re going to do it, too, but you’re just going to have a lot less lawn. You’ll keep your lawn manicured and you have swaths of grass. It’s going to be a mechanism for moving around your property. It’s a great way to avoid brushing up against vegetation during tick season.

So it does have important benefits, but three or four acres of it? Nah. I mean, we can do better than that.

You mentioned invasives. Gardeners point to a plant they grow and say, “I’ve never seen it self-sow, so I don’t think it’s invasive here.” But that’s probably not the litmus test, is it?

When I first started giving these talks some 20 years ago, people frequently talked about how English ivy was not invasive in the East — a problem in Oregon, but not a problem here. So now it is.

It’s tough. There are places in the country where certain plants will never be invasive. It’s too dry, or it’s too something. So it’s not like that never occurs. But if it has invasive tendencies, it typically means something’s moving it around — either the wind, or it’s often birds taking berries and pooping them out someplace else.

Burning bush, for example: One bush makes like 30,000 seeds. A mockingbird eats a few of them, flies off. You don’t see that reproduction in your garden, but it’s in the woods two acres away. Migrating birds in the fall, particularly, can fly 300 miles in one night. And they’re pooping on the way.

There are so many good plants we can use that are not harmful. Why do we insist on using the ones that have already proven to be harmful, at least someplace?

As gardeners get planting this spring, I know you want them to incorporate keystone plants — a term you have popularized, and one of your big principles.

The term is from Robert Payne’s ecological literature in the ’60s, and he realized that particular species are playing outsized roles in their ecosystem. He worked with starfish or sea urchins and tidal pools.

But then we looked around and said, “Well, a lot of species have keystone roles.” Like beavers. You take the beaver away, the whole pond disappears, and everything that depends on it. Elephants are keystone players on the Serengeti.

But it hadn’t been applied to plants before. And we realized, looking at host-plant records, that just 14 percent of our native plants are supporting 90 percent of the caterpillars that are the bread and butter of terrestrial food webs. That 14 percent is really important.

So we can talk about native and nonnative, and that’s what we were talking about before we knew this. But I could make a 100 percent native landscape that supports very little.

And if the goal is restoring ecosystem function and food-web integrity, you’ve got to have the plants that do that. So it’s nice that we figured this out, but it does make it a little bit more complicated, because now you have to choose the most effective plants.

There are keystone plants for making caterpillars. There are keystone plants for supporting pollinators. And ideally we want both of those.

But the first question you asked me is, how does somebody who’s got an established garden improve it without tearing the whole thing apart? Look at the plant choices you have, and add some keystone plants, like the ones in Homegrown National Park’s regional guides. That is the way to boost the productivity of your garden tremendously without removing anything.

Out of all the things that my lab has done over my entire career, I think the most important, most far-ranging thing is ranking plants in every U.S. county in terms of their ability to support the food web.

We’ve just finished a list for the entire world, so now we’ve got to get it out there somehow. Because I hear about these reforestation efforts, I hear about the trillion-tree effort, and it’s all based on climate change.

But a trillion eucalyptus is what? A lost opportunity. Yes, it’ll sequester carbon, but it could support biodiversity at the same time. What plants are the best wherever you are? That’s the information we want to provide.” [1]

1.  The Four Ecologically Crucial Things You Should Do in Your Garden. Roach, Margaret.  New York Times (Online) New York Times Company. Apr 9, 2025.