Article by Catherine Bacque

Recently I attended a screening of the Imax film Flight of the Butterflies at the Ontario Science Centre. The film is a new Canadian documentary, directed by Mike Slee and produced by SK Films, about the discovery of the yearly migration of Monarch butterflies and the successful quest of Dr. Fred A. Urquhart (U. of T. Scarborough) to track them to their overwintering grounds in the volcanic mountains of Mexico. It was a wonderful surprise to see that many scenes in the movie were filmed on and under our Scarborough Bluffs, at Cathedral Bluffs and Bluffers Park. I highly recommend the film to anyone interested in Monarchs, or just a great Imax movie experience. It is well suited to all ages and would be an excellent field trip for students, although it might be a bit long for preschoolers.

Having said that, if you want to see what is happening right now with the Monarchs, go to and you can track the 2013 migration north of the Monarchs. There is also lots of information there about Monarchs and milkweed, much of which is very suited to a junior audience. The website is also a fabulous source of information, and has opportunities to get involved in monitoring and aiding the Monarchs.

That’s the good news. The bad news, widely reported in the press recently, is that the number of butterflies counted in Mexico this winter was the lowest ever recorded. While experts and government officials of the three countries involved may argue about who is doing what, habitat loss and use of pesticides are the clear culprits. Fir trees where the insects overwinter are being logged illegally in Mexico, and milkweed is being wiped out across the US and Canada.

Unfortunately, milkweed has long been on the lists of noxious weeds in most North American jurisdictions, as it is toxic to livestock. On the other hand, cattle generally avoid it, so poisoning it is really overkill (no pun intended). Only in recent years has legislation begun to be repealed in many areas to allow people to grow milkweed.

Leading Monarch expert Lincoln Brower says the widespread use of the herbicide glyphosate, sold as Roundup, is now the critical threat to the monarchs’ food supply.

“Glyphosate was developed by the U.S. agricultural biotech company Monsanto, and other herbicide manufacturers have helped make glyphosate the top-selling herbicide in the U.S. And it’s not just the milkweed’s decline that directly impacts monarchs. At their adult stage, the insects need nectar that can come from all kinds of plants, especially wildflowers, which are also being decimated by glyphosate.”

From: Why the monarch butterfly migration may be endangered

By Daniel Schwartz, CBC News, Mar 21, 2013

As a result, Monarchs face a huge challenge finding milkweed, which is the sole host plant for their eggs and caterpillars. It is absolutely critical to their survival. They may also lay eggs on butterfly weed (Asclepias tuberosa), a garden centre find, but the common wild varieties such as Swamp Milkweed (Asclepias incarnata), with longer thin leaves, and the wide-leaved Common Milkweed (Asclepias syriaca), are the ones with which most of us are familiar, and are the most available to migrating Monarchs.

Asclepias incarnata

Asclepias syriaca

What to do? Plant milkweed, of course! Unfortunately, milkweed seed is not particularly easy to buy, however the wonderful advocates at have supplied the following list of sources for Ontario:

You should consider the right kind of milkweed to plant for your area, and the easiest way to plant the right milkweed is to collect seed from plants in your neighborhood in the fall. Failing that, try to get Incarnata or Syriaca and scatter them around in a sunny well drained place. I have found that doing them favours like extensive soil preparation and manure/compost almost never works, so scraping up the surface of the soil and scattering seed as they might fall naturally is good. That being said, Mother Nature lets seeds go in the fall, not the spring, so if you want to fool them, stick any that you buy or collected last fall in the freezer for a week or two before planting.  If you are eager to get started right away, the Stewardship Garden site from New York State has a very good website for folks who want to start seed indoors. Go to Our Habitat Garden for full details.

Milkweed really does seem to thrive in poor soil conditions and waste spaces like cracks in concrete and spaces between paving stones. I have had some good success transplanting the ones that come up in inconvenient spots, but if you wish to move a baby milkweed, take care to get the whole root system and not break the main root or the plant will die. They are perennial, so once you plant one, it should return for you.

On a final note, anyone who loves the Monarchs can also advocate for the planting of milkweed in public spaces. In addition, a concerted effort needs to happen to eradicate the Pale Swallowwort (also known as Dog Strangling Vine) that has infested so many milkweed patches. It is a severe threat to Monarchs, as it is extremely invasive and overruns our native milkweed. Because it is related to the milkweed family, Monarchs can become confused and lay eggs on the imposter, which means that their caterpillars will emerge onto plants which will not sustain them and they will die. Learn to recognize the Swallowwort and tear it out wherever you find it.

Pale Swallowwort or Dog Strangling Vine (Cynanchum rossicum)

A word of caution… the seedpods of the Swallowwort will scatter seed everywhere unless the plants are removed carefully. At this time of year you will not likely see the pods, but if you do, take care not to spread the seed around. As it emerges in the spring, Swallowwort will be very shiny and green, unlike the milkweed, which will be not as shiny and a bit paler in colour.

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