Baptisia australis provides garden beauty from the first emergence of graceful stems to the overwintering seedpods, and is also an early-season food source for bumblebees.Credit…Mt. Cuba Center
The New York Times
By Margaret Roach
In recent years, the demand for pollinator plants has surged. But most of us don’t have room for a meadow.
So where do these native plants fit in your garden, which may not be that big and is probably not very wild-looking? And how do you find plants that are native to your particular location, with the highest value to beneficial insects and, in turn, birds and other native wildlife?
One of the first places I saw native plants being cultivated was outside Wilmington, Del., around 1992, at Mt. Cuba Center, a former du Pont family estate that is now a native-focused public garden, with more than 50 acres of display gardens on over 1,000 acres of natural land. It is also a research facility, where large-scale trials are conducted on selected varieties of native annuals, perennials and even shrubs, testing for garden worthiness, disease resistance and appeal to the insects who have evolved alongside the plants.
#1 Nature plants in layers, as seen in this springtime image of Mt. Cuba Center in Delaware — not by sticking a giant tree in the middle of a sea of diversity-lacking lawn.Credit…Mt. Cuba Center
George Coombs, Mt. Cuba’s director of horticulture and former trial-garden manager, has watched a lot of native plants in action. We discussed some general principles to help gardeners get started finding, and using, the best natives for their location and goals.
Get Oriented — the Way a Plant Does
Although a nursery tag may say “native,” the species could hail from a completely different sort of area. That’s because plants don’t observe state boundaries, but rather habitats within regional zones, like coastal plains or forests with particular soils, light and moisture conditions.
Any native planting can help — at least in a small way — to bridge the gaps in our fragmented, overdeveloped habitat. But what should you emphasize?
“Think about what kind of wildlife you want to attract,” said Mr. Coombs, who has seen up close the appeal of Monarda to butterflies and hummingbirds, and how Baptisia is “a great early-season food source for bumblebees.”
A water garden that remains unfrozen year-round attracts birds, dragonflies and more.
Focus on Welcoming Insects, Rather Than Pretty Plants
Butterfly and moth caterpillars are essential components of food webs that sustain other native creatures, specifically songbirds, many of whom feed the insects to their young. “Grow bugs” is a kind of mantra for habitat-style gardeners, which means using no insecticides or other chemicals.
But Where to Make Room?
In many residential settings, shrinking the lawn — which doesn’t offer pollen, nectar or seed, because we mow it — is a prime opportunity.
I have what I like to think of as “unmown” islands within my garden, creating small meadows of whatever came up (little bluestem grass and goldenrod, mostly), which I then edited. I’ve transformed other grassy areas into planting beds for native trees, shrubs and perennials.
You could also rethink a grass strip along the property line, inside a fence or hedge, that you may currently mow right up to, or that may be planted with nonnative ivy, pachysandra or vinca. Even a six-foot-wide swath transitioned to native ground cover and fruit-bearing shrubs enhances diversity.
Despite having the smallest flowers of all the tall garden phlox trialed at Mt. Cuba, the cultivar Jeana was the most appealing to butterflies.
Credit…Mt. Cuba Center
Formal Spaces and Containers Can Hold Natives, Too
At Mt. Cuba, when the estate’s traditional gardens were transformed into native landscapes, it was “a great opportunity to showcase natives in a more traditional, formal setting that a homeowner could adapt in their own landscape,” Mr. Coombs said.
In one spot, long planted with summer garden annuals, the shift to native perennials included plants like Phlox Forever Pink and Echinacea tennesseensis.
Mt. Cuba’s pots are swapped out three times each season with a mix of perennials and shrubs. In spring, a deciduous native azalea in a large container might be surrounded with woodland phlox (Phlox divaricata), purple-leaved heuchera and fringed bleeding heart (Dicentra eximia).
“Last fall, we did pots of Muhlenbergia grass that were stunning,” Mr. Coombs said.
Best of all, the plants can be overwintered in the vegetable garden and used again, or incorporated into the garden.
Plant in Layers, the Way Nature Does
One such opportunity: Enlarge those diversity-lacking mulch circles beneath trees in a lawn, making room for native woodland shrubs as the middle layer, then herbaceous perennials beneath.
“No bare soil,” Mr. Coombs advised. “And your ‘ground cover’ can be three feet tall — that’s fine.”
Even the formal gardens by the estate house at Mt. Cuba have been transformed into native landscapes. In spring, Penstemon Dark Towers, Tradescantia Concord Grape, Gillenia trifoliata Pink Profusion and Artemisia Valerie Finnis show off in the south garden.
Credit…Mt. Cuba Center
Plan for a Succession of Blooms
That way, you’ll support more than one moment in native organisms’ lives.
In a mixed ground-cover planting, don’t choose all spring-flowering things and then have nothing on offer later for insects or birds.
“A lot of people go to the garden center in spring and just buy what’s blooming, but it’s important to think about what’s happening later,” Mr. Coombs said. “Go back in September and see plants you didn’t see in the spring.”
Even better: Call ahead with a wish list based on research. “Talk to your garden center about plants you hope to grow and why,” Mr. Coombs said. “In a roundabout way, the more they hear from customers, the more they will stock natives.”
Choose a Diversity of Flower Shapes and Sizes
“A hummingbird plant is very different-looking than a butterfly plant,” Mr. Coombs said, noting that even within a single genus, the size and shape of the flower parts can vary enough to appeal to an entirely different clientele. “In our Coreopsis trials, the species’ different morphological characteristics predicted what type of bee would prefer it — this bee’s tongue would match it, where another’s cannot.”
To figure out which plants pollinators are frequenting, researchers from the University of Delaware, led by Douglas W. Tallamy, have been conducting scientific pollinator studies in the Mt. Cuba trial garden.
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“The variety called Jeana was the one attracting the most butterflies,” Mr. Coombs said. “But we’re not really quite sure what characteristics were bringing the butterflies in. Its flowers are actually the smallest out of any garden phlox, somewhere between a pea and a dime.”
In fall, the south garden at Mt. Cuba blooms with native perennials, including Solidago sphacelata Golden Fleece, Penstemon Dark Towers, Coreopsis palustris Summer Sunshine, Symphyotrichum laeve Bluebird, Stokesia laevis Peachie’s Pick and Artemisia Valerie Finnis.
Credit…Mt. Cuba Center
Not All Cultivars Are Created Equal
To pollinators and other animals that interact with plants after long coevolutionary histories, the closer a variety is to the straight species (as nature’s version of each plant is called), the better.
Breeding changes made to please gardeners, like double flowers, don’t get high ratings. In the smooth hydrangea (Hydrangea arborescens), for instance, the popular cultivar Annabelle, a mophead type with mostly sterile bracts, cannot sustain as many insects as the original lace-cap flower arrangement.
Maybe most dramatic: Leaf-color changes made in a cultivar from green to purple or red can be unpalatable to insects that rely on the plant. Red and blue pigments, called anthocyanins, don’t taste as good as chlorophyll.
Manage the Garden Differently
Don’t clean up too obsessively or too soon, especially in the spring and fall, as beneficial creatures need leaf litter and other hiding places to overwinter and reproduce. “We prolong our cutbacks till later winter or early spring — one of the last things we do,” Mr. Coombs said.
And as a compromise between horticulture and ecology, “you can even mulch in place,” he said. “Cut four-foot stems into pieces and let them lie rather than carrying them away to the compost.”
Even for the Pros, It’s an Experiment
“I always tell people that it’s OK to fail,” Mr. Coombs said. “Don’t worry, trial and error is how we create a lot of our gardens at Mt. Cuba. Yes, we may have had a design in mind, but sometimes the garden has its own idea what will grow there and not. You will have to take direction from Mother Nature.”
The American painted lady butterfly, Vanessa virginiensis, enjoys one of the phlox cultivars in the Mt. Cuba trial garden.
Want to really drill in? Most states publish an online flora, a database of plants present in the state, native and not, down to the county level. Some outstanding examples are the New York Flora Atlas and Calflora, for California. (Search for your state’s name and “flora” or “state flora of.”)
“Nature’s Best Hope,” Douglas W. Tallamy’s new book, is a guide to transforming our home landscapes into more diverse places.