The Case Against Mulch Rings

grounded design by Thomas Rainer: The Case Against Mulch Rings: It’s a common sight in the American landscape: trees skirted with a ring of mulch around their base that float in a sea of lawn.   Landscap...

Asking More of the Landscape At Plant-O-Rama in Brooklyn, the Message Was That Beauty Is No Longer Enough

[Plant-O-Rama: never heard of it, but sounds irresistible. db]

“I can’t believe I’ve been running this event for 19 years, but you seem to keep coming back,” Bob Hyland told the cheering crowd at the Brooklyn Botanic Garden’s auditorium last week. “A few growers from the North Fork are still digging out of 30 inches of snow. But they’re with us in spirit.”

The storm had postponed Plant-O-Rama for two days, but it hadn't dampened the enthusiasm of the more than 1,000 plant lovers who are drawn to this symposium and horticultural trade show every year with an urgency akin to that of the swallows returning to Capistrano. (Mr. Hyland, a former vice president of horticulture at the Brooklyn garden, had flown in from his home in Portland, Ore.)

No matter that snow covered the witch hazels. Spring was on the way.

Plant-O-Rama has been a bellwether for trends in the garden world since its founding in 1997, by Mr. Hyland and other leaders of Metro Hort Group, a network of New York-based urban horticulturists. Exotic species as well as natives have ignited plant lust here, depending upon which rock star of the garden world extolled their virtues on the big screen in the darkened room. But always, the focus has been on aesthetics: what makes an attractive garden.

Last week, the keynote speaker, Douglas Tallamy, an ecologist, informed us that beauty is not enough.

“We have to raise the bar on our landscapes,” said Mr. Tallamy, a professor and chairman of the department of entomology and wildlife ecology at the University of Delaware. “In the past, we have asked one thing of our gardens: that they be pretty. Now they have to support life, sequester carbon, feed pollinators and manage water.”

A daunting order, perhaps, but maybe it’s just a shifting of gears. Yards filled with beautiful natives that can provide all of these services don’t have to look unruly and formless. And they are key to survival, Mr. Tallamy argued. Pollinators, he reminded us, “pollinate 90 percent of all plants, not just crops.” And if the plants crash, so do the rest of the species, including us.

Landscape ecologists estimate that only 3 to 5 percent of the lower 48 states is undisturbed habitat for plants and animals. Farmland now covers more than half of the country. Most of the rest is taken up by suburban sprawl and about 40 million acres of lawns (“eight New Jerseys,” as Mr. Tallamy put it), along with highways, malls and growing cities. A world with half those lawns, he said, might have 20 million acres of habitat, or more than 13 national parks, including Yellowstone, Yosemite and the Adirondacks, if you added up the acreage.

Instead, thanks to vanishing habitats, Mr. Tallamy said, “We have 50 percent fewer birds than 40 years ago,” referring to results of yearly bird-banding studies that track those numbers. And some 230 species of North American birds are at risk of extinction, he added, citing the 2014 State of the Birds Report (stateofthebirds.org).

“But we can do something about this,” he said. “We can bring nature back to our yards.”

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Plant-O-Rama’s theme this year was Living Landscapes, a nod to Mr. Tallamy’s latest book, “The Living Landscape: Designing for Beauty and Biodiversity in the Home Garden,” written with Rick Darke, a horticulturist and photographer whose own native garden in Newark, Del., is strikingly beautiful.

The book, published last year by Timber Press, comes seven years after Mr. Tallamy’s best seller, “Bringing Nature Home,” which described the lifeline that native plants provide to native fauna, particularly insects and birds. But his first book didn’t show how native plants could be layered, with winding paths in between, to make a garden as lovely to people as it is to its other inhabitants.

As Mr. Tallamy admitted, “I'm not a designer.” But Mr. Darke does have a gift for design, and the new book shows how a garden can function as an ecosystem and still have a powerful form.

Trees, of course, are carbon sinks. A large native sugar maple sequesters 450 pounds of carbon a year; a white oak, 513 pounds. Millions of such trees planted in American yards, Mr. Tallamy said, could help reduce global warming. Yet landscape contractors and designers often discourage clients from planting oaks and sugar maples.

“They say, ‘You won’t live long enough to enjoy an oak tree,’” Mr. Tallamy said. “But it doesn’t have to be 300 years old.”

He flashed an image of a white oak seedling on the screen, planted by a blue jay in his yard in Oxford, Pa. Fourteen years later, the tree is 20 feet tall and 13 feet wide. It’s a handsome tree, for sure. But so is a zelkova, or Japanese elm, you might argue, and that sequesters carbon, too. The difference is that native oaks support 557 species of caterpillars. The zelkova, none.

Gardeners worry that all those caterpillars will defoliate their nice shade trees, Mr. Tallamy said, and then pointed to his white oak: “I counted 410 caterpillars, of 19 different species, just walking around this oak for half an hour one July day last summer. It wasn’t defoliated. You couldn’t see the holes.” (And even if you can, don’t think of those holes as damage, he said. Think of them as evidence that you’re feeding your friends.)

He counted the caterpillars on one of his black cherry trees: 239 in 14 species. In contrast, a Bradford pear in his neighbor’s yard had just one species, an inchworm.

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Mr. Tallamy is relentless with his facts: 90 percent of native insects have developed specialized relationships with native plants. The blue flowers of Phlox divaricata, a native ground cover, for example, have too narrow a corolla for bees to reach the pollen. Only native hummingbird moths and a few other insects have a proboscis long and narrow enough to reach the pollen and nectar.

And another thing: Most plants defend themselves with toxic compounds. But certain native insects with the right enzymes have evolved alongside specific plants to break down the plant’s particular chemicals.

“Eastern red cedar has been around for millions of years, but very few insects, except the Juniper hairstreak, can eat its tissues without dying,” Mr. Tallamy said. “The downside is, that’s the only thing it eats. So if we don’t include cedars in our yards, we lose the hairstreak.”

 

And the only host for the great fritillary butterfly is the native violet. “When violets are mowed down,” he said, “we lose the fritillaries.”

And if we lose the insects, including spiders and moths, we lose amphibians, bats, rodents.

“Even the fox eats insects — 25 percent of his diet is insects,” Mr. Tallamy said.

So it goes throughout the food web. Though nonnative plants may provide nectar for butterflies, their leaves are unpalatable to caterpillars. Images of weirdly gorgeous worms flashed before our eyes. Caterpillars with little curvy tails or blue neon bumps or fuzzy mops of brown hair, chomping leaves of willow, black cherry, oak and other native species. “Streak dagger moths, Cecropia moths, spiny oak caterpillars,” he said, reeling off a dozen other names.

These caterpillars aren’t just entertaining to look at: 96 percent of all terrestrial birds in North America eat insects. And their young can’t survive without them.

Mr. Tallamy flashed images of bluebirds, catbirds and warblers, their beaks full of caterpillars, stuffing them down the throats of their voracious young. “Chickadees need 6,000 to 9,000 caterpillars to feed one clutch,” he said.

Mr. Tallamy had watched a pair feeding their young in a nesting box suspended from his white oak tree. The birds delivered 17 species of live caterpillars to their babies in three hours, sometimes carrying two or three at a time, every three minutes. No coffee breaks for these parents. They hunted worms from 6 a.m. to 8 p.m. for 16 days, until the nestlings fledged.

Watching these kinds of interactions is more engaging than watching the grass grow (and mowing it). And it can create a sense of place.

“At our house, spring comes when the woodcock returns,” Mr. Tallamy said. “We know it’s fall when the juncos show up.”

Of course, not all of us are about to give up our beloved lilacs and tree peonies. And many are still married to those garish Japanese azaleas that Mr. Tallamy loathes.

“But are they ruining the landscape?” he asked. “No, they’re just taking up room that a native plant could occupy.”

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Ruth Rogers Clausen, an English-born perennials expert who has gardened in this country for a half-century, followed Mr. Tallamy with a talk about her own favorite native plants. And it must be noted that her latest book, “Essential Perennials: The Complete Reference to 2,700 Perennials for the Home Garden,” written with Thomas Christopher and recently published by Timber Press, is as enthusiastic about a Japanese tree peony as a native prairie flower.

“As far as our book is concerned, we didn’t push one way or another,” said Ms. Clausen, 76, who gardens in Easton, Md. “Putting in an Asian plant doesn’t make you a bad person.”

But environmental consciousness has raised the bar, she allowed. “I came to the first Plant-O-Rama, and almost every one since,” Ms. Clausen said. “People used to not ask where a particular plant came from. Now they want to know, especially the young people.”

 

In her own garden, she said, she strives for at least “a minimum of 50 percent natives, just to make sure that I’m looking after wildlife.”

Ms. Clausen, who grew up in South Wales, recalled that many plants in her mother and grandmother’s garden were American natives. “We had a hedge of New England asters that bloomed every fall.”

She suggested all kinds of lovely combinations.

Bloodroot, the ivory woodland flower that blooms so early and fleetingly, could be tucked beneath a deciduous tree to flower while its branches are still bare. “But don’t plant the double one, if you want wildlife,” she said. (Many varieties of species, gussied up by hybridizers, lose their value for wildlife.)

Mix bloodroot with trilliums (if you don’t have deer), columbine and native gingers, which have shiny evergreen leaves.

Virginia bluebells are striking mixed with celandine poppies, though the poppy “is a generous seeder,” she said, and can be invasive in some gardens. In the wild, native bluebells flourish with ostrich ferns.

Ms. Clausen mentioned sun-loving zizia, or golden alexander, as one of the best plants for the black swallowtail butterfly, and noted that spigelia, with its upright stems of deep red flowers, draws the hummingbirds.

Amsonia, a native mounding perennial, covers itself with blue stars in spring and turns a golden orange in fall, she said, and “it looks gorgeous en masse.”

Both she and Mr. Tallamy encouraged gardeners to visit Mt. Cuba Center (mtcubacenter.org), a botanical garden near Wilmington, Del., and a former du Pont estate, which demonstrates, in hundreds of acres, how natives can be artfully combined. Ms. Clausen loves the fields of native coreopsis and rudbeckias encouraged along the roads near Easton.

“I stood on the brakes on Route 50 for this field of Coreopsis grandiflora,” she said. And a field of Rudbeckia hirta, black-eyed Susans, caused her to hit the brakes on Route 301.

She loves to put such natives in her garden, but the popular variety, Goldsturm, leaves her cold. “It looks like plastic,” she said. “It’s very flat.”

Many other favorites of hers may be found in “Essential Perennials,” along with her favorite exotics, like the epimediums she has nestled beneath the old native beech tree in her backyard. (“Don’t tell Doug,” she said.)

If the natives get 50 percent of her garden, perhaps the rest goes to nonnative plants that bring back memories of home, or dear friends. “I love the Welsh poppy, because I come from Wales,” she said. “I love the old-fashioned fragrant dianthus that my grandmother grew.”

But the specialized relationships between the native species fascinate her: “The whole thing is an enormous jigsaw puzzle, and when you find a piece, it’s exciting.”

In “A Living Landscape,” Mr. Tallamy tells the story of the Atala butterfly, a native of South Florida that once thrived on its sole host plant, Zamia pumila, or coontie, a slow-growing native cycad. The butterfly disappeared as the coontie was harvested to the point of extinction, to make starch out of its roots.

But in the mid-1970s, landscape designers rediscovered coontie as a valuable evergreen that could take drought and heat. And as coonties began to fill South Florida yards, the Atala butterfly returned.

“Maybe it had been harbored in the Everglades or somewhere,” he said, but “adding that single plant brought the butterfly back.”