Milkweed: Major pillar of North American ecosystems & high-performance insulator
Common milkweed (Asclepias syriaca), also called Soyer d'Amérique in French, is a plant native to North America that colonizes unused fields, vacant lots and even roadsides.
Nature lovers and even beginners recognize it easily. Whether in bloom, with its almost perfectly spherical flower umbels, or when its pods split open, full of seeds and white floss, milkweed catches the eye of passersby.
To see it up close, from flower to floss: the field tour.
Common milkweed is the best-known and most widespread species of the subfamily Asclepiadoideae, itself part of the dogbane family (Apocynaceae), which includes more than 2,000 species. Its natural range extends from Québec to Texas, north to south, and from Oregon to Nova Scotia, west to east. It is the species grown commercially in Canada for its white floss, which is insulating, water-repellent, rot-resistant and light.
In Québec and Eastern Canada, 4 milkweed species are native:
- Common milkweed (Asclepias syriaca), with pink flowers
- Swamp milkweed (Asclepias incarnata), with mauve flowers
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Butterfly milkweed (Asclepias tuberosa), with orange flowers
- Poke milkweed (Asclepias exaltata), with white flowers
A gold mine for pollinators
The abundance and diversity of insects that visit milkweed is no accident:
- It overflows with sugar-rich nectar (3%).
- Its pollen is also renewed throughout the life of the flower, which is unusual.
- Its flowering period is also unusually long compared with other plants, about 4 weeks for a colony.
A few of the many pollinators that visit milkweed flowers. More photos of pollinators in the photo library.
Host plant of the monarch butterfly
Milkweed is the exclusive host plant of the monarch butterfly (Danaus plexippus). Their symbiotic relationship goes back millions of years and is so complex that science has yet to unravel all of its mysteries.
- Milkweed sap naturally contains substances called cardenolides, which are toxic to most animals, including many of the monarch's predators and parasites.
- Female monarchs lay their eggs exclusively on milkweed plants found along their migration route, from Mexico to Canada.
- The caterpillars feed on milkweed leaves to self-medicate against parasites and to become toxic to many of their potential predators.
- The caterpillars form their chrysalis near the milkweed plant they hatched on. The butterfly that emerges there will feed on milkweed nectar, among others (helping pollination), but also on other flowers, depending on the time of summer it emerges.
What makes this special is that instead of breaking down or excreting the toxins in its food, as many animals with similar behaviour do, the monarch larva accumulates them in its tissues and keeps them even after it becomes a butterfly. The concentration of cardenolides in a monarch caterpillar or butterfly is therefore much higher than in a milkweed plant, making them effectively toxic to many predators and parasites. A few other specialist insects (milkweed bugs, the milkweed longhorn beetle, the milkweed leaf beetle and the milkweed aphid, etc.) have also developed the same evolutionary strategy, sporting the same colours as the monarch.
Since the relationship is symbiotic, milkweed also shows signs of co-evolution with the monarch and other herbivores. The plant seems to heal faster and faster from attacks by its herbivorous predators, the monarch caterpillar among them. Its reproduction also depends in part on pollination by adult monarchs, which feed on the abundant nectar of its flowers.
It becomes almost impossible, then, to describe the monarch without mentioning milkweed, and vice versa. To learn more: the monarch butterfly, and our FAQ on harvesting and monarchs.
Milkweed floss as a high-performance thermal insulation
The fibres attached to milkweed seeds are what is commonly called American silk or Québec silk. These hollow fibres, shaped like almost perfectly round micro-tubes, trap air and create a thermal, acoustic and water-resistant barrier that is surprising for a plant material. When milkweed floss is used as a filling or laid out as an insulating textile membrane, the air held inside the fibres (the lumen) adds to the layers of air trapped between the fibres. This property creates an effective barrier against heat transfer, making it possible to make outdoor accessories that are thin and light, with a level of thermal insulation that holds its own against synthetic or animal-based materials.
Another interesting property makes the fibres even better suited as a lining for outdoor clothing: they are naturally coated with a wax that makes them hydrophobic, meaning they repel water. So on top of keeping you warm, milkweed-insulated clothing keeps you dry! That is an impressive advantage over other textile insulations on the market, such as down, polyester or wool, which soak up water easily and hold on to moisture, while having a much greater ecological and ethical impact.
And the advantage is twofold: milkweed repels moisture from the outside (snow, rain, etc.) as well as from the inside (sweat).
What this means in a product. This insulation, grown and processed in Québec, is what we put in our mittens, neck warmers and scarves, coats and jackets and insulated bags. To understand what is made here and what is assembled elsewhere, see our Transparency page.
Other industrial uses
Flotation material
A bit of history: during the Second World War, when Japan cut off the supply of kapok from Asia, milkweed was harvested on a large scale in Canada and the United States for its textile fibre, used to fill the life vests of sailors and airmen. Thanks to its hydrophobic properties, milkweed floats for up to 8 hours straight. Of course, all of this was before synthetic materials came along. Sadly, this potential has since been abandoned.
Oil spill absorbent
The same goes for the many other economic uses of milkweed. One of the most promising today is without a doubt as a high-performance absorbent for oil spills. The same tubular fibre structure that gives the fibres their insulating property also makes them lipophilic, meaning they can hold oily substances. Needless to say, this characteristic would be very useful for containing petroleum spills in aquatic environments. Weight for weight, milkweed absorbs 5 times more diesel than the material most widely used for this purpose today (polypropylene), while floating perfectly and absorbing no water at all! Milkweed is a very promising alternative here, especially when you consider the irony of today's oil absorbent industry, whose products are made from... petroleum!
Bedding fill
Milkweed floss is also used as a fill for bedding and pillows, on its own or blended with down. Being hydrophobic, it repels moisture and helps keep the pillow dry. It is what fills our milkweed pillow.
Cosmetics
The oil extracted from milkweed seeds is being closely studied for its potential as a base for cosmetics, such as skin lotions or sunscreen. Through a chemical process, it is indeed possible to turn the triglycerides in milkweed oil into compounds that absorb UV rays. At Lasclay, cold-pressed oil from the seeds already goes into our skin care: soaps, creams and pure oil.
Milkweed is right here, all around us: all that's left is to gather it.
Want to sow some? Our milkweed seeds cover several native species, with a planting guide to get you off to a good start.
