>>Audubon At Home
The New Gardeners
in the offing, it's not too early to think about ways to grow flowers
and vegetables that are as healthy for your yard as they are for the
birds and insects visiting it. Follow the lead of visionaries from coast
to coast who have kicked the chemical habitat. By Garry Hamilton
Photograph by Brian Smale
Keith Geller stands amid a cluster of trees that could easily pass for a mature forest but is actually the front-yard centerpiece of his Seattle home. "This is the migrant trap," says the 52-year-old landscape architect, pointing toward a dappled green canopy that closes in multiple tiers overhead. It's a surprisingly harmonious mix of natives and carefully chosen nonnatives, all tucked into a space barely big enough to park a Winnebago. Geller recites the name of each species as if they were old friends: Dogwood. Vine maple. River birch. Magnolia. Pacific wax myrtle. Bay. Scot's pine. Plum. Pear. "Lots of native birds find this very attractive," he says. "I counted five different warblers and two vireos in here one morning, and that was quite exciting."
A few yards away the wilderness mirage continues with a small pond covered with water plants and surrounded by lush carpets of oxalis, fringe cups, Oregon grape, and wild ginger. A mix of fernsmaidenhair, deer, sword, and Alaskanform lacy green fountains among evergreen huckleberry, red huckleberry, beautyberry, and red flowering currant. There are roughly 75 different plant species in total, all sharing a 60-by-120-foot lot with a two-story bungalow, a detached garage that's been converted into an office, and two courtyards.
In contrast with the rest of the neighborhood, where vast expanses of lawn and sparse plantings are the rule, this urban Eden already qualifies as a dream garden. What makes it even more attractive is that Geller refuses to use chemicals. Instead of resorting to insecticides, herbicides, or fungicides, he employs a diverse repertoire of alternative strategies to avoid ever needing chemicals in the first place.
One approach is physical intervention. Geller removes slugs by hand, for instance, and takes care of aphids with a blast from the garden hose. At the same time, the Seattle Audubon Society member follows rules, such as making sure the right plant goes in the right place, that are essentially the tenets of good gardening. "I had a problem in one area with root weevil for a while," he says. "But then I took the plants out, replaced the soil, and let it go empty for a while. I've since replaced it with other plants, and that seems to have solved the problem."
Finally Geller lets nature do much of the work. Having a diverse community
of plants provides a year-round home for birds and beneficial insects,
and they help control the bad insects. By mulching and not tilling,
his soil retains moisture and teems with beneficial soil microbes. This
prevents the spread of disease-causing fungi and other problem soil
organisms. It also makes for hardier plants, which are better able to
crowd out weeds and use their own natural defenses against both microbial
and insect pests. It's a more balanced backyard ecosystem, on
the whole, and it largely fends for itself.
A major force behind the trend is a growing awareness that even in the post-DDT era, pesticides continue to wreak havoc on the environment. "Reducing the nearly 102 million pounds of pesticides, herbicides, and fungicides we use in our homes and gardens each year would improve the quality of the water flowing into rivers and help maintain the diversity of wildlife found in those waters and beyond," says Paul Green, Audubon's director of citizen science and acting director of the Audubon At Home program. The goal of the program is to encourage people to practice personal conservation in their own backyards. The stakes are high. Each year, for example, 72 million birds die in the United States from exposure to pesticides.
A dramatic example of the threat pesticides pose to wildlife occurred in Argentina in 199596, when an estimated 20,000 Swainson's hawks, or 5 percent of the world's population, died following spraying to control grasshoppers. Besides direct poisoning, there are less obvious side effects that are only now coming to light. In Seattle, for instance, scientists recently discovered that when commonly used pesticides run off into surface water, they can disrupt a salmon's sense of smell, the same homing mechanism these fish use to return to their spawning grounds. What's more, there is evidence that the widespread decline of amphibians in North America is at least partly due to pesticides. In one study researchers noted that amphibians were far less numerous in lakes and rivers that were situated downwind from farms. Other research has found that pesticides increase the rate at which amphibians develop physical deformities. As for humans, the evidence linking pesticide exposure and numerous serious health problems, including cancer, is now so strong that in April 2004 doctors in Canada began advising patients to avoid using pesticides whenever possible.
In addition to these fears, more gardeners are turning away from pesticides because the chemical approach to gardening just doesn't make sense. One reason is that reliance on a single weapon invariably breeds resistance in the very pests you're trying to do away with. Another is that pesticides also kill the natural enemies of pests, disrupting the processes that nature uses to keep ecosystems in balance. This explains why serious pest outbreaks recur more readily after the repeated use of pesticides.
The first step toward kicking the chemical habit lies in mimicking the way nature builds a balanced ecosystem. By tolerating pests in small numbers, and by growing a variety of plants that provide nectar at different times and flowers of all shapes and sizes, you can establish a permanent and diverse biological pest-control community. Shrewsbury did a study on yards with azalea bushes, examining why some had lace bugs, a notorious azalea pest, while others didn't. The key was diversity. "I found that landscapes that had more structural complexitymore plant material, more trees, more shrubs, more flowers and ground coverwere less likely to have lace bugs," she says. "And that related directly to the number of natural enemies in the landscape."
Plant selection is also important in building a stable web of life
in the backyard. Native plants generally offer the best solution, since
they interact with other local species in beneficial ways scientists
are only beginning to understand. But ecologists are also starting to
see the urban landscape as a unique ecosystem, one with soil chemistry
and other characteristics distinct from those under which local plants
have evolved. As such there is now a new tolerance for the idea that
nonnatives may be able to fill niches within this urban ecosystem. "Sometimes
in the context of a backyard, diversity can best be achieved by considering
some nonnatives along with natives, taking care that we're not introducing
invasive species by doing so," says ecologist Tess Present, Audubon's
senior scientist for ecology and conservation science.
Jennifer Wilson-Pines of Port Washington, New York, offers a good example. A political and conservation leadershe is an elected official and the appointed deputy mayor of her village, as well as president of the North Shore Audubon Societythe 48-year-old Wilson-Pines has been gardening since she was a small girl. In 1995, when she bought her 50-year-old suburban home and its small yard, it was essentially an ecological wasteland. The soil was porous (her house had been built on a former sand mine) and so nutrient-poor that not even weeds would grow. The garden did have three large Norway maples, two of which were later found to be infected with the soil fungus verticillium.
To bring her garden back to life, Wilson-Pines focused first on the soil, restoring it to health with as much compost as she could generate. She chose plants that would attract wildlife, steering clear of anything susceptible to verticillium. And when her two diseased maples finally died, she had one lopped off at 15 feet to act as a standing snag for insects and birds.
Today Wilson-Pines has plants in bloom from early February right through to Christmas, including hellebores, early crocuses, late crocuses, tulips, daffodils, woodland phlox, yarrow, coreopsis, asters, black-eyed Susans, coneflowers, bee balm, flowering dogwoods, chokecherry, shadblow, butterfly weed, lantana, goldenrod, dill, chives, oregano, and chrysanthemums. Her tiny paradise is now visited by ruby-throated hummingbirds, goldfinches, red-winged blackbirds, yellow-bellied sapsuckers, and hairy, downy, and red-bellied woodpeckersbirds that had never before ventured near. It's also a permanent residence for swarms of beneficial insects. "Usually in the fall, when the leaves are down, I take a head count of praying mantis cases, and I find anywhere between 8 and 12," she says proudly. "They thrive because my yard is densely planted, has lots of nectar sources and prey, and lots of places for them to hang out."
As a result Wilson-Pines has had little use for chemical interventions.
"The garden seems to be taking care of itself," she says.
"I've had exactly two tomato hornworms, and they were both so heavily
parasitized with wasp eggs that they couldn't move when I found them."
Of course, nature isn't perfect, a fact that leads to the second phase of alternative pest managementwhat to do when problems do arise. According to Sharon Collman, an entomologist who helped found Seattle's Master Gardener program in the 1970s, the first step is to not panic. Even when pests are present, they're often not causing any great harm. Or they may already be under the control of natural enemies such as parasitic wasps, lady beetles, or green lacewings. "Sometimes it's just a case of adjusting your tolerance level," she says. If a problem is serious enough to warrant attention, Collman adds, gardeners need to understand that plenty of nonchemical options are available. Insects and infected leaves can often be picked off by hand. Mites can be washed off using the garden hose. Tent caterpillars can be removed by pruning. Fungal diseases can be contained by avoiding overhead watering. The list goes on.
Usually a problem will require a combination of such strategies, depending on where gardeners live, what they grow, and how much time or effort they're willing to devote to the problem. Consider longtime Lane County Audubon Society member Reida Kimmel, 63, who lives on six acres in a valley outside Eugene, Oregon. A semiretired scientific research assistant at the University of Oregon, she now spends much of her time raising sheep, chickens, and turkeys, and growing tomatoes, squash, corn, zucchini, peppers, apples, pears, and numerous other crops that make up the bulk of what she and her husband, Chuck, eat during the year. She also puts a great amount of effort into providing habitat for her property's native wildlife, which includes such vulnerable species as northwestern salamanders and red-legged frogs. For these and other reasons she avoids using chemicals at all costs, instead handling pest problems with a combination of creative thinking and trial and error.
To combat slugs, Kimmel surrounds her lettuce and spinach with a layer of crushed oyster shells, which act as a barrier (and also help neutralize her acidic soil). She also lays down boards and pieces of plastic to serve as breeding grounds for garter snakes, which gobble up her slimy pests like candy. When Kimmel was plagued by asparagus beetles, she began interspersing her asparagus with daffodils, columbines, lupines, onions, and other plants the beetles find unpalatable. During peak beetle season, she also started picking her asparagus spears as soon as they emerged. This kept the beetle numbers down while still allowing her plants to establish healthy root systems that produce bumper crops later in the season. "I've gone from having horrible asparagus bugs to almost having none," says Kimmel.
Of course, there will be times when no amount of clever thinking will be enough to solve a pest problem. For purists like Kimmel, the response is to either live with the damage or not grow the plant. Others, however, say there is room in alternative pest management schemes for some pesticide usebut only as a last resort and only in ways that respect the integrity of the backyard ecosystem. This means choosing less-toxic substances, such as horticultural oils, insecticidal soaps, or naturally toxic agents, such as the bacterium Bacillus thuringiensiscommonly known as Bt. You should remember, though, that even these agents can do harm as well as good.
One person who takes this approach is Ruth Troetschler, a Santa Clara Valley Audubon Society member who lives in the suburbs of Los Altos, California. A biologist who specializes in insect physiology, Troetschler spent many years helping to develop safer and more specifically targeted pest-control systems. Now 79 and retired, she is the coauthor of a book about natural pest control called Rebugging Your Home and Garden. Like a lot of other IPM practitioners, Troetschler has filled her quarter-acre property with buckwheat, fennel, alyssum, and other plants that help nourish and attract beneficial insects such as parasitic wasps. Unfortunately, these natural enemies alone can't keep up with the hordes of coddling moth larvae that inevitably show up in Troetschler's 16 fruit trees. She tried tackling the problem in a nonchemical way, going so far as to wrap each hanging fruit in a bag. When this proved impractical, she began complementing her nontoxic efforts with small doses of less-toxic pesticides. She sprays only after her trees have dropped their blossoms, a precaution that spares bees and other insect pollinators. She also uses pheromone traps, which allow her to track the coddling moth life cycle so she knows when the pests are most vulnerable. "I keep a record every single week of the number of insects in the traps," she says. "And I only spray at appropriate times." Rather than having to spray up to 15 times a yearthe regimen some chemical manufacturers recommend for certain areasshe gets by with having to do it just twice.
Regardless of how you go about it, gardening with little or no chemicals ultimately has an even greater advantageit alters the relationship you, as a homeowner, have with your yard. For those who have entered into this new relationship, the rewards include a deeper level of fulfillment. As Keith Geller puts it, "You become a steward of the land."
© 2005 National Audubon Society