The Journey of the Monarch Supergeneration

Sometime this month, a monarch butterfly will lift off from a meadow on the Oak Ridges Moraine and begin a journey that ranks among the longest in the insect world. It will fly up to 4,000 kilometers to a mountain forest in central Mexico that it has never seen.

Every Monarch that hatches in your garden between June and August lives the same short life: two weeks as a caterpillar, two weeks as a chrysalis, then about four weeks as an adult spent almost entirely on mating and laying eggs on milkweed plants. But the Monarchs emerging in late August and September are different. Triggered by shortening days, cooling temperatures, and aging food source, this final "super generation" skips reproduction entirely, redirecting all its energy into fat storage and endurance. These butterflies can live six to eight months, enough time to fly to Mexico, spend the winter clustered by the millions in the oyamel fir forests, and start the journey home in spring, all without ever having made the trip before.

A monarch hanging onto the chrysalis from which it recently emerged.

In December 2023, Canada formally listed the Monarch as Endangered, with North American populations down an estimated 22 to 72 per cent over the past decade, driven by habitat loss, herbicide use wiping out milkweed, and logging on their Mexican wintering grounds.

But we've been lucky enough to see the other side of that story too. Monarchs have turned up on about 75 per cent of the properties the Oak Ridges Moraine Land Trust protects, a good sign for how much this landscape still means to them.

You don't need to own land to help. Milkweed is the only thing Monarch caterpillars eat, so if you're planting this fall or next spring, go beyond Common Milkweed. Swamp Milkweed does well in wetter, low-lying spots, and Butterfly Milkweed prefers dry, sunny soil and brings a bright orange bloom. A mix of the three covers pretty much any yard.

Keep an eye out for bright orange wings this month. You might spot Monarchs resting and fuelling up as they prepare for their incredible journey. 

Monarch on a Cup Plant.