Bringing Nature Home: Why Native Plants Matter

Palamedes Swallowtail buttefly caterpillar on the leaf of its host plant, Red Bay (Persea species). Photo by Sharon Dolan.

The science is in. If you want birds, butterflies and other wildlife, you need native plants.

What does the extinction crisis have to do with our yards? As it happens, a lot. And to a great extent, we have Dr. Douglas W. Tallamy, professor and Chair of Entomology & Wildlife Ecology at the University of Delaware, to thank for helping us understand the connection.

Chances are, you’ve heard about the ability of native plants to survive the heat, humidity, unpredictable cold snaps and sandy soils of Florida. The idea that native plants are naturally adapted to local conditions makes sense – after all, the woods survive just fine without sprinkler systems, fertilizers and lawn services. With water restrictions here to stay, many municipalities encourage the use of native plants to reduce long-term irrigation needs. You care about preserving natural resources, so the benefits are appealing and make sense. What many of us haven’t yet realized is the role that native plants play in creating landscapes that preserve life as we know and love it.

We learn in school that plants are a fundamental life support system for almost all creatures, including ourselves. Through photosynthesis, plants use sunlight, water and carbon dioxide to create energy stored in plant tissues and release oxygen that we breathe. About a third of all animal species are insects that eat plants. Many of the remaining animal species eat plants and/or rely heavily or solely on insects that eat plants. A familiar example to gardeners are birds, which eat fruits and seeds from plants as well as insects.

But no bugs, no birds. Many gardeners put out bird seed to attract birds and enjoy seeing them up close. While some adult birds will eat the seeds put out, many will not, and no baby birds will be fed. Some 96% of our land-dwelling birds rely on insects to feed their babies. Pound for pound, insects contain more protein than beef and are essential food for baby birds to quickly develop strong bodies. Parent birds may feed their nestlings dozens or even hundreds of butterfly and moth caterpillars each day, adding other insects as needed for additional benefits – spiders, for example, contain more taurine, an amino acid that helps birds grow smarter and bolder.

But what does this have to do with native plants? It turns out that native plants support more insects, and more different types of insects, than non-native plants. This has been demonstrated by scientific studies comparing suburban landscapes that are similar in size, total plant cover, numbers of species, presence of birds boxes, feeders, baths and water sources, and other surrounding characteristics. The only difference between compared landscapes was the mix of native vs. non-native plants. Not surprisingly, the presence of more native plants and thus more insects in the landscape also correlated with increased numbers of birds, greater diversity of bird species, and more pairs of breeding birds.

Most non-native plants have been selected not only for their appearance, but because few or no insects will eat them here. If we put mostly non-native plants in our landscape, we can expect to have far fewer insects, and thus far fewer birds. If a plant does not produce food for anything else, it is, in a natural sense, unproductive. In our landscape, it might as well be plastic.

Why are native plants so much better at supporting insects and as a result, the rest of the food chain? Over thousands of years, the plants and insects that live together in a particular place adapt to each other and become interdependent in order to survive and thrive. One of those important interdependencies is the insect’s ability to feed on the plant. The majority of insects are specialists, meaning that they can eat only a narrow range of plant species. Plants protect themselves chemically from being eaten by insects. Every plant species has a unique leaf chemistry that deters most insects. But some insects will adapt, chemically and physically, to eating the plant. This adaptation takes thousands of years. Move the insect to a place where the plants have different leaf chemistries and it will starve.

Unfortunately, for the past several decades, gardeners have been obsessed with getting rid of insects. This obsession has led to several harmful practices: the widespread and excessive use of dangerous pesticides; less densely planted landscapes than those found in nature; the removal of important organic elements from the landscape such as decaying plants and leaf litter; and a focus on non-native plants that are “pest free,” or largely ignored by insects.

Without natural limits on their population, such as insects that eat them, non-native plants have the potential to tip the balance of nature, invading natural areas, taking over space from native plants, and reducing biodiversity. One example familiar to many Floridians is the invasive non-native melaleuca tree, which in its native country of Australia is eaten by more than 400 different insects. But in the nearly 100 years since its introduction to Florida, only eight different insects have been observed eating it (and none in significant quantities).

Less than 5% of the land in the U.S. remains undisturbed. We’ve converted the rest to cities, suburbs, farms and roads that no longer work as ecosystems. Vast tracts of natural area have disappeared, reduced to isolated preserves and private lands that must be “managed” to retain their natural ecosystem functions. The management process frequently includes the removal of invasive non-native plants and animals. Some 40 million acres of forest have been converted to non-native turfgrass lawns that look green, but are generally lifeless except for chinchbugs, mole crickets, fleas and fire ants. Despite the fact that Florida’s climate is generally inhospitable to turfgrass and potable water supplies are endangered, we continue to convert much of our landscapes to turf and select mostly non-native ornamental plants. The overall result: significantly reduced biodiversity and lifeless landscapes.

Scientists have determined that the number of species that will survive our destruction of their habitat is a simple percentage of the amount of habitat we leave undisturbed: a 1:1 correspondence. If we take 95% of the land, we’ll end up losing 95% of the species that originally inhabited the land – if we stay on our present course. But we have a choice, and we now know that what we plant, matters. We can reduce the amount of our landscapes devoted to turf and we can replace that area and more with native plants. This guide gives examples of just a few of the beautiful native plants now available to home gardeners. All of these plants are beneficial to insects and other wildlife, and your native nursery can advise you on the species that are especially attractive to insects.

What will your life be like with a yard full of insects? First, don’t fear that insects outside means more bug problems inside. You’ll be planting for wild bees, beetles, butterfly and moth caterpillars and other insects that don’t want to live in your house. Bugs in your house are different types, best controlled by good housekeeping. Second, don’t worry about your plants being eaten up by insects. The wonderful thing about nature is that everything is in balance, as long as natural diversity is maintained. Your insects will attract birds, which are highly motivated and very efficient bug eaters. Studies show that as much as 10% of the foliage in your yard can be eaten by insects before anyone even notices. But if you are observant and see insect activity, celebrate. It’s a sign that your yard is working, supporting life as nature intended.

What about insects on your non-native plants? Maybe you’re confused because you’ve seen insects on your non-native ornamentals. Certainly there are insects that will visit your non-natives. About 10% of plant-eating insects are generalists, meaning that they will eat a variety of plants. Some of these generalists may be using your non-natives, although preliminary studies indicate that even generalists prefer natives. And of course, non-native plants are often imported along with their non-native insects and diseases, some of which have proved disastrous to both ornamental and food crops. An example is the Asian citrus psyllid, which is threatening Florida’s citrus industry with greening disease. The psyllid arrived on non-native ornamental plants shipped all over Florida. So yes, there may be some insects on your non-native plants, but they won’t be enough, and may not be the kind we want or need to support our natural environment.

Dr. Tallamy tell us to “garden as if life depends on it,” because it does. Plant native.

[Information presented here is drawn directly from Douglas W. Tallamy’s book, Bringing Nature Home, How You Can Sustain Wildlife With Native Plants, 2009 Timber Press, updated and expanded version.]

This feature made possible with the financial assistance of the Coccoloba Chapter and Serenoa Chapter of the Florida Native Plant Society, serving Southwest Florida.