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Homegrown: Choosing native plants helps keep the environment healthy

  • PHOTO COURTESY OF DOUG TELLAMY<br/>The Zebra swallowtail is butterfly whose larvae or caterpillars feed on pawpaw. Caterpillars of a relative, the black swallowtail, feed on members of the carrot family, including parsley and dill.

    PHOTO COURTESY OF DOUG TELLAMY
    The Zebra swallowtail is butterfly whose larvae or caterpillars feed on pawpaw. Caterpillars of a relative, the black swallowtail, feed on members of the carrot family, including parsley and dill.

  • PHOTO COURTESY OF DOUG TELLAMY<br/>The blinded sphinx moth is related to the sphinx moth that produces the dread tobacco hornworm. The white appendages are eggs of a parastical wasp that helps control the moth population.

    PHOTO COURTESY OF DOUG TELLAMY
    The blinded sphinx moth is related to the sphinx moth that produces the dread tobacco hornworm. The white appendages are eggs of a parastical wasp that helps control the moth population.

  • PHOTO COURTESY OF DOUG TELLAMY<br/>Doug Tellamy, author of "Bringing Nature Home: How You Can Sustain Wildlife with Native Plants," is the keynote speaker at the master gardener symposium on March 16. He is an entomology professor at the University of Delaware.

    PHOTO COURTESY OF DOUG TELLAMY
    Doug Tellamy, author of "Bringing Nature Home: How You Can Sustain Wildlife with Native Plants," is the keynote speaker at the master gardener symposium on March 16. He is an entomology professor at the University of Delaware.

  • PHOTO COURTESY OF DOUG TELLAMY<br/>Milkweed bugs feed in groups and keep the population of wild milkweed under control, leaving plenty of plants for the monarchs but preventing the milkweed from taking over landscapes.

    PHOTO COURTESY OF DOUG TELLAMY
    Milkweed bugs feed in groups and keep the population of wild milkweed under control, leaving plenty of plants for the monarchs but preventing the milkweed from taking over landscapes.

  • PHOTO COURTESY OF DOUG TELLAMY<br/>This colorful caterpillar morphs into the Monarch butterfly, which lays its eggs on the plant so its larvae will have food

    PHOTO COURTESY OF DOUG TELLAMY
    This colorful caterpillar morphs into the Monarch butterfly, which lays its eggs on the plant so its larvae will have food

  • PHOTO COURTESY OF DOUG TELLAMY<br/>Red-bellied woodpeckers enjoy suet from the feeder during the winter but can eat their weight in insects year-round. Like most woodpeckers they extract insect larvae from tree trunks as well as eating flying insects, such as beetles and grasshoppers, in season.

    PHOTO COURTESY OF DOUG TELLAMY
    Red-bellied woodpeckers enjoy suet from the feeder during the winter but can eat their weight in insects year-round. Like most woodpeckers they extract insect larvae from tree trunks as well as eating flying insects, such as beetles and grasshoppers, in season.

  • PHOTO COURTESY OF DOUG TELLAMY<br/>The Zebra swallowtail is butterfly whose larvae or caterpillars feed on pawpaw. Caterpillars of a relative, the black swallowtail, feed on members of the carrot family, including parsley and dill.
  • PHOTO COURTESY OF DOUG TELLAMY<br/>The blinded sphinx moth is related to the sphinx moth that produces the dread tobacco hornworm. The white appendages are eggs of a parastical wasp that helps control the moth population.
  • PHOTO COURTESY OF DOUG TELLAMY<br/>Doug Tellamy, author of "Bringing Nature Home: How You Can Sustain Wildlife with Native Plants," is the keynote speaker at the master gardener symposium on March 16. He is an entomology professor at the University of Delaware.
  • PHOTO COURTESY OF DOUG TELLAMY<br/>Milkweed bugs feed in groups and keep the population of wild milkweed under control, leaving plenty of plants for the monarchs but preventing the milkweed from taking over landscapes.
  • PHOTO COURTESY OF DOUG TELLAMY<br/>This colorful caterpillar morphs into the Monarch butterfly, which lays its eggs on the plant so its larvae will have food
  • PHOTO COURTESY OF DOUG TELLAMY<br/>Red-bellied woodpeckers enjoy suet from the feeder during the winter but can eat their weight in insects year-round. Like most woodpeckers they extract insect larvae from tree trunks as well as eating flying insects, such as beetles and grasshoppers, in season.

The clarion call to landscape with native plants instead of imported species is getting louder. Adding to the argument is entomologist Doug Tallamy, who offers a cogent explanation about how native plants need native insects that pollinate our flowers and add to the food web.

Tallamy, author of “Bringing Nature Home: How You Can Sustain Wildlife with Native Plants,” is the keynote speaker at the annual Spring Garden Symposium in South Deerfield on March 16, sponsored by the Western Massachusetts Master Gardener Association.

“Nature can be defined as the plants and animals in a given area and all of the natural phenomena that made them as they are,” Tallamy writes in his book. It includes the plants, both woody and herbaceous, in our cultivated landscape and in our natural areas as well as the mammals, birds and insects that coexist with plants and, indeed, depend on them.

Today, known invasive alien plants constitute 30 percent of natural areas — due to garden escapes — and 80 percent of our landscaped areas, according to Tallamy. Most of the furor over alien invasive plants has focused on the evidence that they out-compete native plants and eventually dominate the landscape. Kudzu has taken over the South, and Oriental bittersweet, for example, multiflora rose and burning bush are all over New England, and Norway maple is pushing out the native sugar maple.

“There was a big native plant movement before I came along,” Tallamy said last week in a phone interview from his home in Pennsylvania. “All I did was give another reason for planting natives.”

Shunned by insects

It is a logical and important reason, however. Through observation on his own 10-acre property, Tallamy discovered that few insects feed on alien plant species.

“When you look for insects, you look for feeding scars,” he said, adding that there were few to no feeding scars on invasive plants, such as burning bush, Oriental bittersweet, Japanese knotweed and multiflora rose.

Tallamy decided to have one of his students at the University of Delaware compare insect life on native and alien plant species. “There was plenty of research on insects on specific plant species, but nothing comparing aliens and natives, plenty on invasives but nothing about their effect on nature’s food web,” he said.

The research showed that three times as many insects feed on native plants as they do on alien species. And, in terms of caterpillars, “native plants in the study supported a whopping 35 times more caterpillar biomass than the aliens,” Tellamy writes in his book. Native oaks and willows of many species support 400 to 500 kinds of insects in the food web, according to a chart in the book.

We tend to forget that those beautiful butterflies everyone loves start life as eggs that emerge into voracious caterpillars. If there is no food for the caterpillars, they won’t survive to become butterflies. Also, caterpillars are essential parts of the diet of many of our most-loved birds. Mosquitoes are also food for bats — which are threatened by a fungal disease possibly imported from Britain — and for swallows and flycatchers. When native insects, including crucial pollinators like bees, butterflies and birds, can’t find food, they don’t live very long. Many people may be afraid of “bugs,” but they are critical to the ecosystem.

Importation of ornamentals has also led to the arrival of destructive insects and — perhaps even more threatening — destructive diseases.

Bringing in bad stuff

A recent paper by Alexander Leibhold of the University of California at Santa Barbara determined that 58 high-impact diseases came from abroad on ornamental plants. These include the lethal chestnut blight that wiped out native chestnuts in the early 20th century and the current scourge on the West Coast of sudden oak death, Tallamy said.

“The chestnut blight hurt the economies of rural areas from Maine to Florida,” he said. There was a lucrative business gathering wild chestnuts to sell to New York markets, a business wiped out by the blight.

Insect pests such as the Japanese beetle, the gypsy moth and the hemlock wooly adelgid came from abroad, as did the Asian long-horned beetle and the emerald ash borer that is much in today’s news. These insects probably hitched a ride on the roots of ornamentals or in the wood of pallets used for shipping from China.

“We could use plastic crates that could be recycled, but we don’t want to offend China,” Tallamy said.

Plant explorers for centuries have sought to find new ornamental plants to entice gardeners to diversify their landscapes. Many alien or imported species have been brought to this country and advertised as pest-free and low-maintenance, thereby appealing to today’s busy home owner who wants a pristine landscape.

Many of those plants, some of them touted by the United States Department of Agriculture for curbing soil erosion, are now regarded as harmful invasives, and some states are curbing the sale of known invasives such as burning bush and Norway maple. But others are reluctant to take drastic action.

“New Jersey, Delaware and Pennsylvania don’t want to tackle the nursery industry,” Tallamy said. “And anything that is done now is really too late. Oregon just banned English ivy, but if you’ve ever been to Portland you can see it’s about 40 years too late.” English ivy is a popular ground cover on the West Coast as it is in milder areas of the East Coast.

Tallamy says he doesn’t want to make things difficult for gardeners or nursery people; he understands that the nursery industry has built up inventory of popular plants — such as the Norway maple and the burning bush.

“We want to change the landscape industry, not strangle it,” he said. “It’s not required to landscape with plants from China.”

Choosing natives

As an alternative, he urges gardeners to ask for native species.

“Things aren’t apt to change radically until more homeowners ask their local nurseries for native plants. If the nurseryman says, ‘We don’t have that,’ they need to say ‘OK. Goodbye. I’ll go elsewhere.’ ”

A growing number of nurseries are carrying native plants and some are beginning to specialize in them. Nasami Farm, the nursery of the New England Wild Flower Society in Whately, is one such specialist as is Project Native in Housatonic. Tallamy is familiar with Ernst Conservation Seeds in Meadville, Pa., and Prairie Moon Nursery in Winona, Minn. “They go on collecting trips (within the United States) and are good biologists,” he said.

It’s a practice, Tellamy says, that allows for a natural balance among species.

If we limit our plant palette to imported species we are endangering the future of important insects in our ecosystem, Tallamy explained.

Nature does create a certain balance among species, if allowed to do so. For instance the destructive tobacco hornworm, that huge green caterpillar that can destroy a tomato crop in a few days, has a natural enemy. It’s a parasitic wasp that lays its eggs on the caterpillar. When the eggs hatch, the caterpillar provides food for the wasp which destroys its caterpillar host. Thus, nature keeps its own balance. But if you use pesticides to destroy the caterpillar to save your tomato crop, the wasp will lack food. Tallamy said because his landscape is deliberately diverse there are 16 other species of sphinx moths on his property that can provide caterpillars for the wasps. But he leaves the white eggs on caterpillars on his tomatoes.

“I am all for growing food and growing it locally. Growing vegetables and ornamentals is not mutually exclusive,” he said. “Plants support the food web. We need to have many kinds of plants in our landscape.”

Cheryl B. Wilson can be reached at valleygardens@comcast.net.

Related

Spring gardening symposium at Frontier Regional High School

Friday, March 15, 2013

“Bringing Nature Home,” the spring gardening symposium of the Western Massachusetts Master Gardener Association, will be held March 16 from 9 a.m. to 2 p.m. at Frontier Regional High School in South Deerfield. In addition to the keynote lecture by Doug Tallamy, chair of the entomology department at the University of Delaware, there will be two workshop sessions offering a … 0

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