What if you could help boost biodiversity, increase your opportunities for nature exposure and establish robust ecological communities in your own back yard? And what if, by doing so, you could also participate in a grand experiment whose designer dubs it the "biggest conservation effort ever"?
Douglas Tallamy, a University of Delaware entomologist and wildlife ecologist, issued a rallying cry for gardeners and nature lovers in his book Nature's Best Hope: A New Approach to Conservation That Starts in Your Yard. In the book, Tallamy outlines his Homegrown National Park project. The name is a nod to the potential influence of private property owners, who hold deeds to 78 percent of the country’s land.
"Horticulture readers can really make a difference," Tallamy told me in an interview, "because you're already knowledgeable about plants. You can use that knowledge to good purpose." Plants are the foundation of Homegrown National Park, since they anchor vigorous ecosystems by providing food to insects, birds and other animals.
"The task of plants is to store energy from the sun in their leaves and to pass that energy on to other members of a healthy ecosystem," said Tallamy. If they're not doing that, they may look pretty and smell nice, but they're creating a deadscape—a stalemate where the sun's energy stops at photosynthesis and doesn't substantially support other life.
One essential way that native plants in particular contribute to a vital, functional environment is by providing food to caterpillars, which in turn feed birds.
"Chickadees, which weigh about a third of an ounce, need 6,000 to 9,000 caterpillars to raise a single clutch of eggs," Tallamy said. They're not alone. "Most of our birds in North America use caterpillars as a dietary mainstay, especially when it comes to feeding their young."
Investing the time and energy to create a home landscape that emphasizes native plants offers us two big payoffs. First, it's a way to do something that makes the world healthier. We’ve all seen headlines trumpeting the drastic decline of bird and insect species or impending climate disaster. Perhaps we feel a paralyzed resignation. These problems are so enormous, what could one little ol' human hope to do to turn those tides?
"Everything you do on your property affects the rest of the planet—either positively or negatively," he explained. "Think about the piece of property that you can directly influence. Homegrown National Park is a challenge, but it's doable." And for those who enjoy researching and learning about plants, it should be fun, too. And, as a second benefit, it has the potential to put you in contact with a wide, diverse range of wildlife.
"As you include natives in your home landscape, you'll get to see up close the diversification of life that quickly follows," Tallamy said. "You'll see frogs, moths and butterflies; birds will begin to breed on your property; and you'll observe and learn from a parade of native bees, beetles and ants. You'll participate in restoring the world to its glory."
Ready to join the Homegrown National Park? Here's a list of things you can do to make your yard, no matter how large or small, an incubator for biodiversity:
1. Lean into Native Plants
Tallamy recommends planting your property to about 70 percent natives. Online resources can help you zero in on the most appropriate native plants for your area.
With the National Wildlife Federation's Native Plant Finder, you type in your ZIP code and oodles of native plant recommendations, most accompanied by photographs, pop up. Results are ranked by the number of butterfly and moth species that use each entry as a host plant for their caterpillar.
Other resources are available from regional or state-specific organizations. For example, California has the California Native Plant Society's Calscape. With Calscape, you enter a specific address to receive thousands of appropriate native plant suggestions, all of them organized into categories, such as butterfly hosts and low-water plants.
When choosing natives, consider planting straight species over cultivars. Most cultivars are propagated clonally, which means they offer no genetic variability and so they do not adapt to challenges that their location might offer, such as drought or variable weather. Some negatively impact pollinators by producing inferior pollen or nectar, or sometimes, no nectar at all.
"Hydrangea arborescens is native to much of the area east of the Mississippi," Tallamy pointed out. "But a cultivar that's sold at many nurseries, H. arborescens 'Annabelle', is sterile and provides no nectar or food."
2. Shun Invasives
The Homegrown National Park initiative leaves room for compromise. If you have some favorite non-natives, you can still enjoy them, either interplanted with natives or grouped by themselves.
That said, be sure to avoid planting invasive species. They grow and grow and can take over not just your garden, but nearby natural areas, too. Think kudzu vine (Pueraria) in the South Japanese knotweed (Reynoutria japonica) in the Northeast.
3. Reframe Weeds
"A weed is a plant out of place," said Tallamy. "By definition, native plants are not out of place." Unsurprisingly, many native so-called weeds support native wildlife, and often in specific ways. Ninety percent of insects are host-plant specialists, meaning that they feed on just one plant. A well-known example is the monarch caterpillar, which exclusively eats milkweed (Asclepias) foliage. If you select plants with specialist species in mind, you also take care of the generalists, who feed more broadly from many plant species.
Reconsidering native weeds does not mean you need to put up with any old plant that wants to elbow its way into your garden. But you might allow certain North American natives that may have been unfairly labeled—such as Joe-Pye weed (Eutrochium purpureum) and fireweed (Chamerion angustifolium)—to enjoy a space in your plantings so they can strengthen local biocommunities.
4. Tweak Your Outdoor Lights
Lights reduce insect populations, especially moths that feed from nocturnal flowers. Tallamy identified several ways that lights can kill insects: They can die from repeatedly flying into a lit bulb; they can exhaust themselves to death by frenetically flying around a lit bulb; and they can become easy pickings for predators, such as bats, who clean up when bugs congregate around lit bulbs. He suggested two hacks that help moths: Install motion sensors, so that lights only come on when you need them; or replace white bulbs with yellow LEDs, which are far less attractive to moths.
5. Cherish Mature Native Trees
Old, established trees support more life and contribute more robustly to local food webs than new trees. Healthy oaks can live to be 900 years old.
"During its lifetime, a mature oak will pump carbon into the ground through its root system, helping with carbon sequestration" and thus doing working against climate change, said Tallamy, who also authored The Nature of Oaks, a book devoted to the genus Quercus and its ecological value. Big oaks also help with water management, he added: "Their broad canopies soften rainfall, so it's less likely to compact soil, and their extensive root systems encourage rainwater infiltration instead of runoff."