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.

Sweet, sweet nectar

For their all-liquid diet, adult monarchs, like many butterflies, prefer the nectar of brightly coloured flowers, usually in purples, pinks, yellows and whites (perhaps because butterflies have the widest visual spectrum in the animal kingdom). Monarchs, and other butterflies, will flock to gardens with an array of blooms, especially if those blooms have been clustered together to draw attention to the plants. Plant species strategically so the patch is full of flowers throughout the entire growing season.

Some of the monarch’s favourite blossoms are Canadian goldenrod (not to be confused with ragweed, which is the real allergy-culprit), wild bergamot, New England aster, black-eyed Susan, common yarrow and boneset.

Other tricks

“in general,” says Coulber, “maintain your property in an earth-friendly manner, in part by avoiding the use of harsh chemicals and mirroring nature instead.” And a few simple elements can be added to a butterfly garden that will support both local and migratory butterflies, and will improve the likelihood that a large number of monarchs will visit and lay their eggs in your garden:

• A shallow source of water, whether a bird bath or plate, will give butterflies a spot to rest and slake their thirst. Try partially submerging stones to provide perches for the insects while they drink.
• Large stones provide good landing pads and ideal warm spots for absorbing the sun’s energy. Place a few around the garden in areas sheltered by surrounding plants.
• “Mud-puddling” is a behaviour observed mainly in male butterflies. They sit on damp soil and extract minerals with the moisture that are necessary to their reproductive success. Sink a pan, filled with a mixture of garden soil, sand and rich manure, in the garden and keep it thoroughly moist throughout the summer.