If you are worried about the decline of the Monarch Butterfly, you should be just as concerned about the loss of their habitat—the milkweed plant.

Monarch caterpillars need nourishment from the milkweed plant—it’s actually the only plant that they eat—to transform into a butterfly. Then, after they become butterflies, Monarchs use the milkweed plant as a place to lay their eggs. The problem is that these plants are disappearing. Residential and commercial development, changing agricultural practices, pesticide use and other landscaping habits, such as tidying the yard and mowing the grass, are eliminating this critical habitat and reducing populations of Monarchs.

Monarchs are an important part of our biodiversity and an impressive species of insect. In the fall, Monarch Butterflies migrate south to Mexico, where they spend the winter. In the spring, they start their migration back up north, laying eggs on the way. Sometimes, it actually takes a few generations before the Monarchs make their way back to Canada! When the Monarchs finally make it back Canada, they lay more eggs, which hatch, turn into caterpillars and transform into butterflies. The butterflies then migrate back to Mexico to continue this incredible life cycle.

If you want to help support the survival of the Monarch Butterfly, is to plant milkweed on your property—or let it spread if it’s already growing on your land. Monarch caterpillars can feed on any variety the milkweed but there are three that are most common in Halton, which we recommend planting.

Common Milkweed, or Asclepias syriaca, is the most, well, common and seems to be the one preferred by Monarchs. It has broad leaves, round bunches of purple flowers and a beautiful fragrance. Common Milkweed does have a tendency to spread, so you don’t mind it taking over your garden a bit, it’s a great choice.

If you want something a bit better behaved, there are a couple other options: Butterfly Milkweed, or Asclepias tuberosa, has bright orange flowers and is great for gardens that tend to be dry as it is very drought tolerant and loves full sun. Swamp Milkweed, also known as Rose Milkweed, or Asclepias incarnata, on the other hand, has light pink flowers and likes soil that is a little moist, which makes it perfect for a garden that holds a bit of water after rain. This species can do well in regular garden soil but it will not tolerate long droughts. (We have some Swamp Milkweed in the bioswale here at Conservation Halton!)

Planting some fall flowers, such as asters and goldenrods, can also help Monarch Butterflies as they require these plants to sustain them during their long, migratory journey. Again, some varieties of asters and goldenrods tend to spread, so either give them lots of space in your garden or plant some better behaved varieties, such as New England Aster, or Aster novae-angliae, Sky-Blue Aster, or Aster oolentangiense, Stiff Goldenrod, or Solidago rigida, or Blue-stem Goldenrod, or Solidago caesia.

If you do purchase any of these plants, then make sure you only purchase plants grown without pesticides—and, of course, that you don’t use pesticides in your garden. Pesticides that are often used in flower gardens can be harmful and even fatal to caterpillars and other insects that feed on plants that have been treated with them.

We often receive questions about how to collect and raise Monarch Butterflies, either from eggs or caterpillars, but we don’t recommend this without proper training. You actually need a permit to raise Monarch Butterflies and, without proper training, you could end up harming them. If you do want to raise monarchs, make sure you get the proper permit from the Ministry of Natural Resources and Forestry and connect with someone who can teach you how to care for the caterpillars. The best way to help our Monarch Butterflies is to plant milkweed and let nature take care of the rest.

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Last modified: April 5, 2018

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