By Marcus Alegria
The great 1,500–2,000-mile Monarch migration is one of the most mysterious trademark phenomena of North America. This beautiful butterfly, given its name by early European settlers who named the creature “monarch” after King William, also known as “The Prince of Orange” (Urquhart, 1987), continues to delight gardeners as it makes its journey. However, concerns about its numbers are growing. From 1999 to 2010, Monarch populations have declined by 81%. This drop is due to a decline in milkweed (Asclepias spp.) growing in agricultural fields and an increase in herbicide use because milkweed is considered a weed in agricultural settings (Pleasants & Oberhauser, 2012).
However, a weed it is not! Milkweed is the only plant that Monarch caterpillars feed on. Without it, the Monarch cannot carry on with its life cycle. Milkweed also attracts other pollinators into the garden when it blooms throughout the year.
Whether you are a gardener, landscape designer, or just like to grow plants on the porch or balcony, you can participate in the conservation of this great species by growing milkweed.
There are various things to consider if you plan on incorporating milkweed into the landscape. Timing is very important because Monarchs absolutely need milkweed during the spring migration (Dole, 2003). It takes three generations in the spring to make the journey to Canada so they need the milkweed to successfully reproduce during this part of the migration. In the fall, only one generation makes the migration South; therefore, they need plants that produce greater numbers of pollen for energy consumption until they get to Mexico. With this in consideration, the most important time to have milkweed in the landscape is during the spring. High pollen producing plants can be grown during the fall (Dole, 2003).
When selecting the species of Asclepias to grow in the landscape, preference should be given to local species because they are better adapted to the environmental factors of the region. You can look at the Biota of North America Program’s Asclepias page to figure out which species grow locally in your region (Monarch Joint Venture, 2017). Since milkweed is native to North America, you can grow any species you want without having to worry about it becoming invasive. It is believed that certain species are poisonous, so it might be a good idea to keep pets away. In Mexico, some people refer to milkweed as “locoweed” because it supposedly causes insanity among livestock (Urquhart, 1987).
Gardeners could also have their garden certified as a Monarch Waystation. For more information regarding Monarch Waystations, you can visit the Monarch Watch website. Another way that you can help Monarchs out is by growing plants that create adequate ground cover around the milkweed. This will make pupation easier and safer for the caterpillar when it reaches this stage. The picture below was taken within a foot of an adjacent milkweed plant where a caterpillar used the grass as cover during pupation. The chrysalis was left behind by a butterfly either during the previous spring or summer.
Agricultural practices and increased urbanization have had a huge impact on the Monarch butterfly’s success in North America. Growing milkweed to aid Monarchs could also serve as an educational benefit to children, growing conservationists, or to the general public. As gardeners, we have the opportunity to participate in the conservation and success of this great species. Every plant makes a little difference!
Dole, Claire Hagen. 2003. The Butterfly Gardener’s Guide. Brooklyn Botanic Garden Inc. Brooklyn, NY.
Monarch Joint Venture. 2017. Create Habitat for Monarchs. Retrieved Oct. 5, 2017 from https://monarchjointventure.org/get-involved/create-habitat-for-monarchs/
Urquhart, Fred A. 1987. The Monarch Butterfly: International Traveler. Nelson-Hall Inc., Chicago, IL.
Pleasants, John M. and Karen S. Oberhauser. 2012. Milkweed loss in agricultural fields because of herbicide use: effect on the Monarch butterfly population. Insect Conservation and Diversity. 6: 135-144.