Monarch Butterfly numbers are fast declining. In the Monarch butterfly’s wintering area in Mexico, scientists recorded the lowest levels of Monarchs ever in December 2013, a decrease of 44% from the previous year. They are declining everywhere. Here in Ontario, the destruction of Milkweed is the leading factor contributing to their dropping numbers. Common Milkweed up until this year was considered an invasive species in Ontario, and is destroyed every year by farmers using herbicides. Milkweed’s sap is toxic to some livestock and the stickiness of it can cause combines to become clogged during the harvest. Large quantities of Milkweed mixed in with a crop decreases yields and farmers profits; three factors leading to it’s eradication on farms. Milkweed is the only plant Monarch caterpillars feed on and thus the only plant where female Monarchs lay their eggs. As the Milkweed declines, so too does the Monarch.

The life cycle of the Monarch Butterfly is quite interesting. The life span of most adults is two to six weeks. Monarchs that have spent the winter in Mexico are about to start their migration north through the United States and into Canada. As the butterflies migrate north they lay their eggs on Milkweed plants. After laying the eggs the adult butterflies will die two to six weeks later. The eggs then hatch into caterpillars and they begin to feed on the Milkweed plant. After about two weeks the caterpillar attaches itself to a leaf using silk and becomes a chrysalis. This is when the caterpillar begins to change into a butterfly. The chrysalis phase lasts ten days and then the adult butterfly will emerge. Once the adult Monarch has emerged it will feed on the nectar from a variety of plants but the caterpillars only eat Milkweed. The new generation of Monarchs continue north with the new females laying eggs on Milkweed and then dying two to six weeks later. The entire migration consists of four generations of Monarchs with the last ones becoming butterflies in September or October. This generation has a longer life span, six to eight months, and is the one that migrates south to Mexico for the winter. After wintering in Mexico it is this fourth generation that migrates north the following spring to start the cycle again.

Common Milkweed has now been removed from the invasive species list in Ontario, in an effort to save the Monarch Butterfly. If you are reluctant to plant Milkweed because of the potential of it being poisonous to some animals if consumed, simply plant it in an area where your pet can’t access it. Take a look at a list of other common garden plants that are considered poisonous to dogs; many of these plants you may already have in your yard, for instance: Hostas, English Ivy, Clematis and Rose of Sharon to name a few. Adding Milkweed to your yard or not pulling existing Milkweed is the best way to help by giving these butterflies a place to lay their eggs and continue their life cycle. There are several species of Milkweed, so find out which is best suited to your area and yard conditions. Any member of the Asclepias (milkweed) family will do. Have several flowering bushes or fruit tress to first attract Monarchs to your yard and they will quickly find and use the Milkweed for laying their eggs. Flowers that bloom into early fall are important too, as their nectar will provide necessary energy for the Monarch’s long migration south.

Milkweed is the key to the future of the Monarch Butterfly. As it migrates north these plants are imperative to the Monarch’s life cycle and the existence of the species. We can only control what happens in our own backyard so don’t sit back and watch this species decline further. Do your part to help these beautiful butterflies survive and rebound. If you only plant one thing in your garden this spring, make sure it is Milkweed.

Good birding,
Paul