To see a field of common milkweed in midsummer — a sea of a thousand nodding pink flower heads — you wouldn’t imagine that anything could ever stand in the way in which of the genus Asclepias.
Yes, common milkweed (Asclepias syriaca), essentially the most widespread milkweed east of the Rocky Mountains, can colonize disturbed sites and form impressive stands. But it’s an exception among the many greater than 90 recognized North American species of milkweed, a lot of which frequently find it not really easy to proceed making themselves at home.
“The milkweed is a displaced citizen in its own land,” writes Eric Lee-Mäder within the opening of his recent book, “The Milkweed Lands: An Epic Story of One Plant, Its Nature and Ecology.” “Where once it owned the continent, it’s now a sort of vagrant, occupying the botanical equivalent of homeless encampments.”
As one example, he cites 2012 research, by John M. Pleasants of Iowa State University and Karen S. Oberhauser of the University of Minnesota, that estimates an almost 60 percent decrease within the milkweed populations of the Midwest since 1999.
“Milkweeds, a minimum of the North American ones, are like so many other meadow and grassland species,” Mr. Lee-Mäder said in a recent conversation. “They’re each dependent upon us and likewise subject to the assorted indignities of coexisting with us.”
The beginnings of our agrarian legacy set much of their displacement in motion, when vast tracts of original prairie sod were plowed as much as create croplands. Since the Nineteen Nineties, the usage of increasingly sophisticated chemical herbicides that kill all the pieces however the crops genetically engineered to withstand them has essentially “targeted milkweeds for elimination,” he said.
Once, milkweed “would get shredded and pulverized by cultivation equipment, but it surely would spring back from the live rhizomes underground,” he continued. Now, “the milkweed inside those systems just dies.”
We have relegated milkweed to ditches and abandoned lots, said Mr. Lee-Mäder, an ecologist on the invertebrate-focused Xerces Society, where he’s the co-director of pollinator and agricultural biodiversity. He directs the nonprofit’s private-sector initiatives, supporting pollinator-conservation work across hundreds of acres with firms like General Mills, Nestlé and Danone, undertaking habitat restoration on farms that provide them with ingredients like almonds and blueberries.
Mr. Lee-Mäder and his wife, Mari Lee-Mäder, also operate Northwest Meadowscapes, in Port Townsend, Wash., a supplier of regional native seeds that also provides consultation services for meadow makers.
They know something that anyone who gives milkweed refuge will soon learn: If you welcome this plant, a various, living fan base will follow close behind — and never only monarch butterflies.
If you plant it, they are going to come. Sometimes as if out of thin air.
A Two-Way Chemistry Equation
If someone says “milkweed,” perhaps you furthermore may hear “monarch butterfly” in your head. It’s almost as if the 2 are inextricably linked.
Mention of this plant probably also brings to mind stories of its distinctive chemistry. Many plants defend themselves against herbivory by producing unpalatable or toxic chemicals, but “milkweeds take this strategy especially seriously,” Mr. Lee-Mäder writes.
Asclepias produce potent steroids called cardenolides “that may disrupt the life functions of vertebrate animals unlucky enough to feed on them,” he adds. (A bonus: These chemicals may discourage deer.)
But while milkweeds have evolved their chemical defenses to guard themselves, they may “be gifting these chemical defenses to a number of the animals that live in association with them,” Mr. Lee-Mäder said, “as much as using these to envision and control the quantity of herbivory that they need to sustain.”
One notable example: monarchs, which have famously evolved to ingest milkweeds without harm. Their larvae depend on Asclepias as an obligate host plant, or a food required for a minimum of one stage of development. Eating it fosters an anti-predation chemical defense of their very own.
So critical is that this relationship that female monarchs lay their eggs on milkweed leaves, ensuring that the needed sustenance is at hand when offspring emerge.
“They use their olfactory sense to discover the locations of milkweeds on wind currents,” Mr. Lee-Mäder said, “tracking those down like bloodhounds on a trail, to find a way to put their eggs on those plants.”
The monarch-milkweed connection is commonly spoken of as “chemical warfare,” but Mr. Lee-Mäder prefers to consider it as a “two-way relationship” or “a partnership.”
The monarchs’ part: Although the adult butterflies will not be great pollinators, they do visit milkweed flowers for nectar, potentially moving some pollinia (milkweeds’ pollen-bearing structures) long distances during their migrations.
“That gene flow that monarchs may facilitate might be unmatched by other flower visitors to milkweeds,” Mr. Lee-Mäder said.
Not Just Monarchs
As intimate and celebrated because the plants’ relationship with monarchs is, the community surrounding milkweeds is much more diverse.
“The hungry throng” that Mr. Lee-Mäder enumerates includes a minimum of 40 insect species that “feed often or exclusively on North American milkweeds in the summertime,” he writes. They include butterflies, moths, beetles and aphids.
In a milkweed seed-farm field within the Midwest, he recalls witnessing a cloud of aphids descend on the breeze, as if tuned in by GPS to the emerging crops’ location. “It’s like seeing nature form of present itself out of thin air around this plant,” he said.
Before you say, “No, not aphids; not in my garden,” take into consideration their role in the large picture, Mr. Lee-Mäder said — as food for useful insects like lady beetles and lacewing insects, for example, that are, in turn, food for birds. And one of the crucial abundant milkweed-visiting aphids, the nonnative oleander aphid, is host-specific, meaning it doesn’t eat other plants.
Other invertebrates, including slugs, snails and spider mites, may feast on milkweeds, too, as do some larger animals, like rabbits and ground squirrels, that are apparently immune to poisoning.
Beyond so many opportunities for herbivory, Asclepias flowers provide nectar to adult butterflies and moths, together with an astonishing lineup of bee species and wasps.
And just take a look at them: Milkweeds are “amongst essentially the most elaborate within the plant kingdom,” he writes, with “a complexity comparable to that of rare orchids.”
Which Ones to Grow?
It’s easy to take enjoyment of a stand of common milkweed or its Western counterpart, showy milkweed (A. speciosa) — whether in bloom or later, holding their substantial seed-filled pods, or follicles. Lanky as these three- or four-footers could also be, they put you “nose to nose with the wildness of what this genus can represent,” Mr. Lee-Mäder said.
He expresses awe for rush milkweed (A. subulata), a three- to five-foot plant with whitish-green blooms that grows alongside the Joshua tree (Yucca brevifolia) in nearly rainless parts of the desert Southwest. “It’s a plant made up of stems — it produces almost no leaves,” he said, explaining its adaptation for survival.
There are other decisions for gardens with no meadow-size space to supply, though, or people who aren’t in essentially the most arid places.
It’s no surprise that butterfly weed (A. tuberosa), with its vivid orange flowers, has received essentially the most horticultural attention.
“It’s beautiful, it’s compact, it’s charismatic,” Mr. Lee-Mäder said, noting also that orange is fairly unusual amongst prairie and meadow flowers. Although the palette of Asclepias is mostly quite different from East to West, “tuberosa is one which crosses the Continental Divide,” he said, residing even in parts of the desert Southwest.
At nearly two and a half feet high, a mature plant can produce “strikingly abundant blooms for the space that it takes up, and attract a extremely remarkable spectrum of flower visitors,” he added. It can also be pretty much adapted to the customarily highly altered soils of our human landscapes.
As its common name implies, swamp milkweed (A. incarnata), with its distinctive magenta flowers on stems of as much as about 4 feet, can handle it wet. With rain gardens and bioswales increasingly being planted to administer more insistent runoff in a changing climate, this widespread species should get more play. Do you have got a spot for it just beneath a downspout, or perhaps at a pond’s edge?
Another essential but underappreciated species that Mr. Lee-Mäder desires to put in a word for, especially with Western gardeners, is the lavender-and-white-flowered narrowleaf milkweed (A. fascicularis), “one of the crucial widespread breeding plants for Western monarchs,” he said.
Unlike Eastern butterfly populations, which overwinter in Mexico, Western monarchs spend the winter in coastal California after which move inland around March for breeding season. Their clusters break up and typically move straight eastward, into the Central Valley or Sierra Nevada foothills, fanning out from there.
“A monarch that wintered in Monterey might find yourself in Las Vegas or Boise or Spokane that next spring and summer,” he said. They need more narrowleaf milkweed along their routes.
Like so many native plants, milkweeds could have continued only on the fringes in nature, but gardeners can offer them distinguished spots. An excellent place to start researching which of them to decide on is the Xerces Society’s Project Milkweed and its region-specific plant lists.
“Planting milkweeds in a garden could also be a small dent — but it surely’s a dent,” Mr. Lee-Mäder said. “If everybody does it, it’ll add a unique sort of richness to our landscapes.”
Margaret Roach is the creator of the web site and podcast A Way to Garden, and a book of the identical name.
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