Meet the Natives: Common Milkweed, part two

A pasture such as the one shown above could easily be overrun by common milkweed, ruining its value as food for livestock.

Click here for part one.

BANS ON COMMON MILKWEED, a plant that is vitally important to the monarch butterfly, are a sad reminder that the needs of humans and the needs of wildlife do sometimes conflict. However, this dilemma also gives us a chance to explore ways of trying to meet the needs of both. One important lesson is that gardeners in cities, suburbs, and other areas where there is not a lot of agriculture going on have a vital role to play--if they can get over their all-too-common obsession with "neat and tidy" landscaping practices.

The (Sad) Case for Milkweed Bans

Monarchs are threatened, but so are small farms. And as a resident of farm country, I cannot help but recognize that common milkweed might pose a threat to my neighbors' livelihoods.

There is a large (but family owned) dairy farm where I live, for example. The cows seem to be treated well, with access to pasture throughout the growing season. For winter feeding, the farmer cuts hay on a number of local properties. If these fields were to become infested with milkweed (which could easily happen if someone were to introduce it to the area), this hay would be useless. The only way to keep milkweed out of the pastures would be to use one of the few herbicides that's effective on this plant, a solution that would be expensive and that I doubt anyone in the community would want.

This is why several Canadian provinces have passed bans on common milkweed. (But please don't get the idea that Canadians are backward. As far as I've been able to find out, the main reason such bans are almost nonexistent in the United States is that U.S. farmers use more herbicides, making the bans unnecessary.) I think this is excessive, using a chainsaw where a scalpel would be the ideal tool. But I grudgingly admit that I understand how the bans came to be passed.

The Possibility of Compromise

Canada isn't oblivious to the potential impact of these bans on monarch butterflies. Thus far, most of the provinces seem to have dealt with the dilemma by using selective enforcement. In other words, the bans are on the books for use when milkweed becomes a problem, but they aren't enforced unless somebody complains. For example, in 1996 a researcher for the Monarch Watch organization was told that in Ontario, Saskatchewan, and Manitoba, milkweed was being controlled only on a "complaint" basis. Only Nova Scotia had an active eradication program at that time.

Ontario has taken this policy one step further by publicizing its policy of tolerance. In a FAQ at the Ministry of Agriculture website, the province explains, "As long as the population of milkweed planted doesn't negatively affect agricultural or horticultual land by spreading seed and new vegetative plant material (i.e. root stock) into fields, nurseries or greenhouses then it is acceptable to plant milkweed in your garden. It is recommended that you consult with your local weed inspector and/or neighbours so that all parties involved are comfortable that the impact to agriculture or horticulture is negligible."

This is laudable up to a point, but of course any gardener familiar with the Deborah Dale case can see the pitfall: All you need is one complaint by one uninformed neighbor, and the monarch habitat you've been lovingly cultivating will be toast.

Better Options

A better option would be for the authorities to start making more fine grained, more informed discriminations. If a plant is a genuine problem in agricultural areas, for example, perhaps it should be controlled in those areas. But that doesn't mean that it should be banned from areas where there are no farms. On the contrary, property owners in those areas should be encouraged to plant milkweed and other native plants with value for wildlife, all the more so if the plants are banned in certain agricultural zones. In fact, milkweed is an excellent example of why it is so important for people in urbanized areas to create wildlife oases in their own backyards.

Mind you, I'm not saying that I support bans on native plants. What I support is creative compromise, a search for ways of meeting both the needs of humans and the needs of wildlife without causing too much damage to either one. One possibility is to ban certain plants in agricultural areas only, while encouraging or even mandating the creation of wildlife oases in urban zones. But that's not the only option.

Another might be the "lemons into lemonade" approach: Why not turn a plant such as milkweed into a commercial crop? Common milkweed has been cultivated in Europe as a source of fibers* that can be used to make paper, cloth, rope, or a soft insulating material that was used in life jackets during World War II. The flowers have been used to make wine.

The point, again, is that we can find solutions to (apparent) conflicts, as long as we are open to creative compromise. What we cannot afford is simplistic solutions or solutions that pit one group, such as farmers, against another group, such as wildlife lovers. If that happens, both will lose.

* According to the U.S. Department of Agriculture, "Milkweed stems are collected after the stalks senesce in late fall-early winter. The dried stalks are split open to release the fibers; milkweed fibers are sometimes mixed with fibers of Indian hemp (Apocynum cannabinum). The bark is removed and the fibers released by first rubbing between the hands and then drawing the fibers over a hard surface. Twisting the fiber opposite each other and twining them together forms the cord. Often this is accomplished by rolling the fibers on the thigh while twisting them together."

Meet the Natives: Common Milkweed, part one

This beautiful photograph of a monarch butterfly on milkweed is by garden blogger Jodi DeLong. Check out her amazing photographs of monarchs emerging from chrysalides here and here.

WANT IT, CAN’T HAVE IT. That’s the tragedy of my relationship with common milkweed, a plant that is beautiful, easy to grow, almost essential for monarch butterflies … and banned in many places, including Nova Scotia, where I live. When I first learned about laws forbidding me to grow this plant, which is so important to the life cycle of a beautiful and threatened butterfly, I was appalled: How could authorities be so backward? Now that I’ve looked into it a bit more thoroughly, I think I’ve come to understand why the laws exist. I still think the laws probably need to be changed, but I now hope more for a compromise than for a complete end to all restrictions.

But before I talk about laws banning milkweed, let me give you some background on the plant.

Description

Common milkweed (Asclepias syriaca) has thick, erect stems that grow quite tall (4-6 feet) and bear 4-inch pompoms of smaller flowers that look pink to me but are sometimes described as mauve, creamy white, or purplish. As is characteristic of milkweeds, the individual flowers have an unusual hour-glass shape, with some petals pointing downward and others pointing up. When injured, milkweeds “bleed” a milky sap—hence the name.

Common milkweed closely resembles swamp milkweed (A. incarnata), which I’ve written about previously (and which, fortunately, is not banned in Nova Scotia). However, the flower clusters of common milkweed are round and carried up and down the stalk, and the plant has coarse foliage; the flowers of swamp milkweed are flat-topped and carried on the top of the plant, and the foliage is more fragile.

Common milkweed flowers from May to August, the flowers being followed by attractive seed heads that are popular with crafters. The blooms are fragrant; the odor has been described as “heavenly” and as being like that of “hyacinths and lilacs.”

By now no doubt you can begin to see why I want this plant so badly! And yet there’s more.

Value to wildlife

The U.S. Department of Agriculture offers us the following enticing quote: “This is a wonderful horticultural plant for landscaping to attract butterflies (particularly monarchs), whose numbers are declining and migratory routes changing due to lack of appropriate habitat.” Monarch butterflies will lay their eggs only on plants in the milkweed family because the plant contains a chemical called a cardiac glycoside, which is mildly toxic and makes the caterpillars and adult butterflies taste bad to potential predators.

Once upon a time, common milkweed was plentiful in the northeastern United States and lower eastern Canada, and monarchs had all the plants their tiny insect hearts could possibly desire. However, development and agriculture have destroyed many of these stands, leaving monarchs and other butterflies with fewer plants to feed on. Today common milkweed is most often found growing primarily in untended fields and pastures, ditches, and roadsides.

Where, at least in Canada, it is often treated as a weed. Yes, sadly this important plant is banned outright in Ontario, Quebec, Manitoba, and Nova Scotia.* In addition, Minnesota allows individual counties to ban common milkweed if they wish to do so, but there is no statewide ban.

The bans in Ontario and Quebec are of particular concern because these provinces are in the heart of monarch breeding territory. Nova Scotia supposedly is on the fringes of this zone, but as Jodi DeLong's photographs attest (see photo above), monarchs definitely do breed here.

Why a Weed?

OK, milkweeds are toxic. But common milkweed apparently is toxic only when ingested in large quantities. (Some of the other milkweeds apparently are more toxic.) And besides, milkweeds taste so bad that animals usually don’t want to eat them. (This is, remember, precisely why monarchs like them so much.) How poisonous is milkweed? The only documented, naturally occurring (that is, not involving nasty force-feeding of the plant to livestock) case I’ve been able to find took place in Maryland during a drought and was recorded in 1942. Evidently some sheep ate milkweed and died, but they ate the plant only because it was the only food available at the time, because of the drought.

Although anyone who wants to ban milkweed will mention its toxicity, the primary reason for banning it seems to be that it causes problem for farmers. As the province of Nova Scotia explains on its website, "Common milkweed is a competitive weed and can absorb nutrients and water more efficiently than many crops. Therefore, it can reduce crop yields significantly. Because of its rapid spread, it can quickly become a nuisance weed on farmland. Once a field becomes infested, it is very difficult to control. At harvest, the thick sap of common milkweed can clog combine parts. The fluffy seed may also clog air intakes."

Of course, farmers have to contend with many weeds. Unfortunately, milkweed is particularly difficult to control. It spreads readily and has deep roots. "Mechanical control of common milkweed, such as cutting or clipping, simply leads to the creation of larger colonies from the rootstocks of the plant," says Nova Scotia, although the province admits that "continuous cultivation will eventually deplete food reserves in the rootstocks." Common milkweed also does not respond to many of the herbicides used today. However, it can be controlled with glyphosate (often sold under the brand name Roundup), which is generally regarded as one of the safer herbicides in use today. (Many people object to all herbicides; I'd like to sidestep this debate if I can today.)

The bottom line, as the province of Ontario explains on its website, is that milkweed "can have a considerable negative impact to a grower's net economic return."

Tomorrow: Part two, alternatives to outright bans, cultivation

* These and other statements made in this post are based on Internet research. I've done everything I can short of making telephone calls to make sure that my information is accurate and up to date.

Meet the Natives: Swamp Milkweed

ESSENTIAL FOR MONARCH BUTTERFLIES, plants in the milkweed family are such important additions to the wildlife garden that I cannot imagine being without mine.

Shown above with a visiting monarch, swamp milkweed (Asclepias incarnata) grows about four feet tall and bears flat heads of pink flowers in summer or even into early fall. A cultivar called "Ice Ballet" has white flowers, while the cultivars "Cinderella" and "Soulmate" are varying shades of pink. The flowers are followed by attractive seed heads in the fall.

As the name implies, this milkweed is a lover of wet places, making it a perfect addition for any wetland (or just plain wet) garden. Mine is growing in a drainage area that also serves to draw water away from my house. The photo below shows the rock-filled drainage ditch leading away from this mini-wetland, which was just scooped out of our clay-filled soil. As you can see from the photo, the flowers attract hordes of butterflies, and not just monarchs. (These are fritillaries.) Swamp milkweed also attracts hummingbirds, hummingbird moths, and certain beetles.


Milkweeds are essential for monarch butterflies because plants in this family are the only ones monarch caterpillars will eat. The milkweeds contain toxic chemicals (warning: toxic to humans though apparently only in large quantities) that cause the caterpillars to taste bad. This protects them from predators.

In Canada, swamp milkweed is native in Manitoba, Quebec, and Nova Scotia; in the United States, it is native to the Northeast; as far south as Georgia, Texas, and Louisiana; and as far west as North Dakota.

Plant swamp milkweed in a moist spot; heavy soil and/or occasional standing water are not a problem. The site should probably receive full sun, though some sources say that this plant can tolerate part shade. Because it has a long taproot, don't plan to move it after you've planted it. Swamp milkweed will spread slowly by rhizomes, and you can naturalize it by scattering the seeds.

The plant is said to attract aphids, but it's highly unlikely that these insects will kill the plant. If aphids gross you out, try to remember that birds take a different view--"bird ice cream," I call them--and will most likely control any aphid outbreak for you. If deer are a problem in your neighborhood, you'll be happy to hear that they don't like the taste of milkweeds.

For more information on milkweeds, I highly recommend the 10,000 Birds blog entry for July 20, 2007. Ten Thousand Birds is a great blog to follow if you're interested in birds, especially if you're a bird watcher.

For additional information on swamp milkweed specifically, check out "This Week at Hilton Pond" for July 15-21, 2001. While you're there, I hope you'll look around this website. The Hilton Pond Center for Piedmont Natural History sure sounds like a place I'd like to visit. The Lady Bird Johnson Wildflower Center also has good information on swamp milkweed.