Every fall our Ontario population of Monarch butterflies (Danaus plexippus) heads south to overwinter in the mountains of Mexico. In late May, after what feels like an eternity, we finally start seeing Monarchs once again filling our skies with those vibrant wings of orange, making their way to our patches of milkweed to lay their eggs. Milkweed is the host plant for Monarchs, meaning it is the only plant a Monarch will lay eggs on and the only plant a Monarch caterpillar will consume.
Though we’re thrilled to see the Monarchs, we were a bit worried to see that the milkweed plants in our wildflower meadow were a measly 2 inches tall on May 27th. Since Common Milkweed (Asclepias syriaca) typically grows to be about 4-6 feet tall, our plants still had a lot of growing to do!
Female Monarchs prefer to lay one egg per Milkweed plant because that allows the best chance for offspring survival. This is easy to do when Milkweed plants are large and plentiful – caterpillars don’t have to compete for food. When we went searching a couple weeks ago, we found multiple eggs on one plant – a sign that the females are desperate and there are not enough host plants to go around. We even found an egg on a tiny one-inch plant whose leaves were so small it could barely hold a baby caterpillar – let alone sustain a larger one that eats 2x its weight every day!
It’s not news that Monarchs are already struggling to find patches of milkweed to lay their eggs. Monarch habitat has been destroyed because of urban sprawl and industrial development and is further threatened by the obsession with manicured lawns, crops and non-native gardens and the pesticide use that goes along with it. You can do your part this summer to help Monarch butterflies by eliminating pesticide use and planting local milkweed species as well as nectar producing plants to help provide Monarchs and other pollinators with food and nesting sites that are necessary for their survival.
In returning to our wildflower meadow, we’ve found that the Milkweed is growing and some of the eggs have hatched! Some of the caterpillars are so tiny, it’s hard to make out what they are, but some of them have grown to be about 6mm long and have finally earned their stripes! We’re looking forward to witnessing the whole life cycle again this summer!