The monarch butterfly has been likened to a featherweight piece of stained glass that through some miracle flits its way each year from Canada to Mexico.
It is not the most endangered of our insects, but its plight — along with the ills of the honeybee — has made it perhaps the most visible symbol of the fragility of our natural world and our ability to mess it up.
The eastern North American population overwinters in the oyamel forests of central Mexico, but its numbers have plummeted by 90 percent in recent years as a result of the loss of overwintering grounds as well as the widespread elimination of milkweed in the United States linked to increased use of herbicides by farmers.
As the spring planting season continues, it’s nice to know that many biologists believe that home gardeners can play a vital role in sustaining the monarch by providing a network of way stations to mitigate the loss of wildflower habitat.
The woes of the monarch have become a priority for a high-profile family of gardeners in the District: Last week, President Obama’s Pollinator Health Task Force released its strategy laying out efforts by the federal government to aid beleaguered bees and butterflies. One of its key goals is to increase the monarch’s overwintering area more than fivefold and to restore or enhance 7 million acres of pollinator habitat over the next five years.
For Michelle Obama, the measures are more personal and closer to home: This spring marks the second year for her pollinator garden on the South Lawn of the White House, near the existing vegetable garden and beehives that have become themselves symbols of her campaign for better nutrition and health.
But can home gardeners make up for the loss of milkweed on millions of acres of farmland where the use of genetically modified crops has led to the milkweed’s demise? (The crops can withstand the herbicide glyphosate; the milkweed cannot.)
“The monarch doesn’t care where the milkweed grows, and putting it in residential neighborhoods makes perfect sense,” said Doug Tallamy, an entomologist at the University of Delaware, author and expert on wildlife habitat gardens. “It will demonstrate that a united effort by a lot of people can make a difference.”
One of the reasons that the monarch has become the butterfly poster child is the clear link between this particular butterfly and the host plant for its larvae. The monarch butterfly can sup nectar on hundreds of different blooms, but its caterpillars have to eat at one table: a milkweed plant. The plant contains toxins that are taken up by the monarch, making the species unpalatable to predators. The caterpillars, like the adults, are conspicuous, with their yellow, black and white stripes. That evident milkweed-caterpillar connection makes the monarch such an obvious science project in the school garden.
Several species of milkweed are available for gardeners. The two most common perennial milkweeds are the butterfly milkweed, with showy orange flower clusters in June, and the swamp milkweed, with pink blooms a little later. These are the two included in Michelle Obama’s garden. These milkweeds are shorter than other species, and don’t spread as much, so plant enough of them to make a statement. A massing will also support a larger number of monarchs.
From a design standpoint, milkweeds should be placed in a sunny garden with other herbaceous plants that will provide interest before and after the milkweed flowers appear. The pods have their own decorative value — florists love them — and an annual milkweed named balloon flower is grown for the novelty of its seed pods.
The orange of butterfly milkweed pairs well with blue-flowering companions; removing the faded flowers will encourage reblooming. Annual heliotropes or perennial catmints make good combinations, said Allan Armitage, a perennials expert and professor emeritus at the University of Georgia. Lavender, veronica and cranesbills could work as well.
The Smithsonian Institution’s Butterfly Habitat Garden at Ninth Street and Constitution Avenue NW and the Ripley Garden across the Mall on the east side of the Arts and Industries Building are both good places to see milkweed integrated into a garden setting.
At the butterfly garden, you can see the common milkweed — that bane of farmers — now looking pretty good in fresh, unblemished clumps. By late summer, it looks tall, tired and tough. Tallamy says if you grow it, you should cut it back at least by half in June to produce soft foliage in late summer that will be more munchable for the caterpillars. If you do that, make sure there are no larvae on the plant before you chop it.
James Gagliardi, the butterfly garden’s horticulturist, said the common milkweed “is aggressive and may be not as showy as the other ones, but it blends into a meadow or mass planting. If you don’t have the space I’d go with the tuberosa [butterfly milkweed],” he said.
Purple milkweed is a violet-blue-flowered species that grows to four feet or so and spreads, but it is hard to find.
Tropical milkweed is a tender perennial grown as an annual by gardeners who value its attractive, slender foliage and red and yellow flowers that bloom for months. It can be incorporated into beds or used in containers. Native plant devotees and ecologists discourage its use because it is not native and because it harbors a pathogen potentially harmful to monarchs.
One inescapable truth of growing milkweeds: They attract aphids. Andrea DeLong-Amaya, director of horticulture at the Lady Bird Johnson Wildflower Center in Austin, offers this advice: Place one hand behind a stem to support it, and then hose off the aphids with a spray of water. A solution of dish soap will also take care of them. “Milkweeds are always going to have aphids.” she said, “It’s usually not a big problem.”
It is perhaps worth noting that the plant list for Obama’s garden contains two varieties of milkweed but more than 30 other perennials, shrubs and grasses. Why? Because for monarch lifelines, the milkweed is only half the story.
The adult butterflies need nectar-rich flowers to refuel as they travel south in September and October: The problem is that this is a time of year when gardens tend to be low on flowers. This can be corrected by planting late-season bloomers now, especially flowers in the daisy family such as asters and goldenrods. Raydon’s Favorite and October Skies are two showy and floriferous aster varieties. Others are more delicate, including varieties of the calico aster (botanically Aster or Symphyotrichum lateriflorus) named Lady in Black, Coombe Fishacre and Prince.
If you have room, consider big-boned perennials such as New York ironweed, silphiums, swamp sunflower (Helianthus angustifolius), giant sunflower (Helianthus giganteus) and the willowleaf sunflower (Helianthus salicifolius). Improved varieties are available.
Mountain mints are absolute magnets for nectar feeders in late summer. The common mountain mint (Pycnanthemum incanum) “attracts monarchs at an amazing rate,” said Lisa Bright, of Earth Sangha native plant nursery in Springfield. The clustered mountain mint (Pycnanthemum muticum) forms big silvery drifts by August.
Don’t forget annuals, including sunflowers, lantana, tithonia and zinnias. By sowing zinnia seeds into July, you will be assuring a succession of late-season blooms that monarchs find irresistible as they make their way south of the border.
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