Common milkweed (Photo: Sarah Coulber/Canadian Wildlife Federation)
The only option for a growing monarch
Milkweed is crucial — in fact, the survival of this butterfly depends on its abundance. Once hatched, a monarch caterpillar will munch the plant unceasingly (and exclusively) for nine to 18 days, growing to 2,700 times its newly-hatched size. At that point it forms a light-green chrysalis and hangs upside-down for another nine to 18 days before emerging with a fresh pair of wings. Those eye-catching appendages are also warning signs: adult monarchs store the poison from the milkweed’s white juice in their bodies throughout their lives. It makes them foul-tasting and somewhat toxic to potential predators.
The milkweeds (plants of the genus Asclepias), include common milkweed, butterfly weed and swamp milkweed in Eastern Canada, and showy milkweed and green milkweed in Western Canada. These perennials grow in every Canadian province except for Newfoundland and Labrador. They’re easy to grow from seeds — mature pods can be collected in the wild in early fall, or seed packets can be purchased at certain gardening centres. Plant in the spring as soon as temperatures reach 15 C or warmer.
Common milkweed, especially, can spread aggressively, so it can be better suited to large plots than small urban spots. Each of the milkweeds requires slightly different conditions to grow, well, like a weed, so bear these differences in mind when planting. Swamp milkweed, as its name implies, loves moister conditions with full sun, which is why it grows along riverbanks. Butterfly weed, conversely, thrives in well-drained, sandy soil.