How to Raise Monarch Butterflies (in Pennsylvania)

Did you know the monarch butterflies hatching in the northeastern U.S. from August to October will migrate 3,000 miles down to Mexico for the winter? Unfortunately, last winter scientists found that the hectares (ha) occupied by monarchs in their overwintering sites dropped by 59%, 2.21 ha to 0.9 ha. With 1 hectare housing approximately 21 million butterflies, the monarch populations in Mexico have dropped by over 21 million individuals.

This study conducted by the WWF also stated one of the reasons behind the monarch population decline was directly related to herbicide use decreasing milkweed, a plant vital to the lifecycle of these butterflies. 

Monarchs (Danaus plexippus) are a species that go through four migrations over approximately four generations annually. The fourth generation of butterflies is that which emerges from July through October in the northeastern United States. These are the monarchs that will then migrate down to Mexico to overwinter. They will then head back up to the southern U.S. and lay eggs. Each consecutive generation will travel a bit further north until the cycle starts over again. 

How to Raise a Monarch

Monarch caterpillars are prone to fatal parasites, like the Tachinid fly, when left outdoors. Normally this would serve as healthy population control, but as their populations are currently suffering, bringing monarch eggs indoors can provide vital protection for the species!

In order to find their eggs, you must first find a supply of milkweed. The plant likes to grow in full sun and dry soil, and is identifiable by the round seed pods found on its stem. 

It is called milkweed for a reason. When the stem breaks, a poisonous milky liquid will drip out. It’s best to wash your hands if the substance gets on you, and to keep children and pets away from the plant. As long as it’s not consumed, however, you will be okay! 

Monarchs will lay pearl-like eggs on the bottom of these leaves. You can break off the leaf and place it in a tupperware container with holes, or purchase a mesh butterfly container to house them in until they hatch. Once hatched, you’ll need to have a supply of milkweed leaves to feed the caterpillars. They’ll get their water from the leaves and will start to grow. As they get older, they can eat more than one leaf per day, so keep a close eye on them. 

Once they form their cocoon, the caterpillar will emerge as a butterfly within 12 days. Freshly formed, their cocoons are truly beautiful, with gold threads dotting its surface. You’ll know it’s about to hatch when the cocoon turns from a bright green to black.

Let the butterfly come out of the cocoon by itself - do not help it! Also allow it to dry its wings before placing it outside, preferably near some goldenrod or other flowers. 

How to Grow Milkweed

Growing different types of milkweed will also encourage healthy monarch populations. Make sure you plant native milkweed (not tropical!). Plant it on an elevated shelf or surface so that dogs or young children won’t be tempted to mess with it, and to keep its roots contained as they spread easily.

Milkweed seeds need to overwinter in order to grow, so you can plant now in order to see them flower in the spring!

Doing what we can to enhance native plants, especially a variety of native milkweed in and around our yards will directly and positively affect monarch population numbers, and hopefully raise them in the years to come.

References:

B, Jason. Monarch Butterflies Migrate 3,000 Miles - Here's How. National Geographic. https://www.nationalgeographic.com/animals/article/monarch-butterfly-migration

Rendón-Salinas, E. Area of forest occupied by the colonies of monarch butterflies in Mexico, during the 2023-2024 overwintering period. WWF-Mexico. https://files.worldwildlife.org/wwfcmsprod/files/Publication/file/5wx7wlzzjm_Monarch_Butterfly_Survey_Report_Feb_7_2024_.pdf

O, Karen. Eastern Monarch Population Decreases by 59.3% in 2023-2024 Overwintering Season. Monarch Butterfly Fund. https://monarchconservation.org/eastern-monarch-population-decreases-by-59-3-in-2023-2024-overwintering-season

T, Chip. Monarch Annual Cycle: Migrations and the number of generations. The Monarch Watch. https://monarchwatch.org/blog/2020/06/03/monarch-annual-cycle-migrations-and-the-number-of-generations/

Life Cycle. Monarch Joint Venture. https://monarchjointventure.org/monarch-biology/life-cycle#alc

Migration. Monarch Joint Venture. https://monarchjointventure.org/monarch-biology/monarch-migration

Parasites Affecting Butterflies. International Butterfly Breeders Association. https://www.internationalbutterflybreeders.org/parasites-affecting-monarchs/

Top Tools, Resources, and Supplies for Raising Monarch Butterflies through Life Cycle. Monarch Butterfly Life. https://monarchbutterflylifecycle.com/pages/raise-monarch-butterflies-resources

L, Linda. Don't Make This Mistake When You Plant Milkweed (A How-To Guide). Garden Betty. https://gardenbetty.com/planting-milkweed-for-the-monarchs/

B, David. How to Grow and Care for Common Milkweed. The Spruce. https://www.thespruce.com/milkweed-plants-monarch-butterfly-host-2132954