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Monarch butterflies migrating | The Old Farmer's Almanac

Fall Monarch Butterfly Migration: Help Fuel It!

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As brilliantly orange as the Monarchs it attracts, the Butterfly Weed brings our fluttering friends in the garden. Credit: Park Seed
 

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Park Seed
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Travel Safe, Monarchs!

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In early fall, I wave goodbye to the last monarch butterflies that hatch in my garden. They’re about to migrate south—the only butterflies to migrate as birds do! Learn more about this amazing phenomenon—and what food our precious monarchs need along their journey. 

It may take as many as five generations for monarchs to complete a migration south. Imagine flying over 3,000 miles with the Sun as your guide, traveling about 50 miles a day. The eastern population, which makes up the bulk of the monarch population in North America, travels from as far north as southern Canada down south to the border regions of Texas and Mexico, arriving at their roosting sites in November, where they’ll hibernate for the winter. There are also some monarchs that live west of the Rockies, which instead gather in southern California. 

I’m blessed with plenty of the orange and black pollinators for months, from March until October, thanks to my plentiful Ascelpias tuberosa—orange milkweed (also called butterflyweed).

Monarchs normally produce four generations or life cycles in one calendar year, and they go through four stages during one generation. The four stages of the monarch butterfly life cycle are the egg, the larva (caterpillar), the pupa (chrysalis), and the adult butterfly. The four generations are actually four different butterflies going through these four stages during one year until it is time to start over again with stage one and generation one. 

The arrival of the first Monarch butterflies in the spring heralds a season full of color and interest in gardens. Photo courtesy of the USDA.

The Monarch Generations

In February and March, monarchs come out of hibernation to find a mate. They then migrate north and east in order to find a place to lay their eggs.

This starts stage one and generation one. In March and April, the eggs are laid on milkweed plants. They hatch into baby caterpillars, also called the larvae. It takes about four days for the eggs to hatch. Then, the baby caterpillar eats milkweed in order to grow. After about two weeks, the caterpillar will be fully-grown and find a place to attach itself so that it can start the transformation process. It attaches itself to a stem or a leaf and then, using silk, it spins and transforms into a chrysalis. Within the chrysalis, the old body parts of the caterpillar undergo metamorphosis to become a butterfly that will emerge in 10 days and fly away. It feeds on flowers and fruits in gardens for two to six weeks. This first generation monarch butterfly will then die after laying eggs for generation number two.

After eggs hatch Monarch larvae or caterpillars munch on milkweed leaves to grow large.  Photo courtesy of Missouri Botanical Garden.

The second generation of monarch butterflies is born in May and June, and then the third generation will be born in July and August. These monarch butterflies will go through exactly the same four-stage life cycle as the first generation did, dying two to six weeks after they become a monarch butterfly. If the process starts early, there can be a fourth generation in late August.

The final generation of monarch butterflies is different from the others. It’s born in September and October and goes through exactly the same process as the previous generations except for one part: Butterflies don’t die after two to six weeks. Instead, they migrate to warmer climates like Texas, Mexico, and California, where they hibernate for six to eight months until it is time to start the whole process over again.

The Right Food for Monarchs

With their numbers plummeting in the last few decades by as much as 90%, monarchs are in real trouble. However, you can help fuel their migration!

Monarchs must time their migration to coincide with milkweed growth. No milkweed means no monarchs

  • Monarch larvae (caterpillars) eat only milkweed, which contains all the vitamins, minerals, and other nutrients needed to transform the larvae into butterflies.
  • Adult butterflies also rely on milkweed as a nectar source, as well as backyard flowers.  

Vivid orange milkweed (Asclepias tuberosa) in my garden is a magnet for monarchs.  The native plant is easy to grow, drought-resistant and a colorful addition to flower beds.

Flowers for Monarchs

  • To attract and help adult monarch during their fall migration, plant milkweed, of course, native flowers, and a few fruit-bearing trees.
  • They like to drink from mushy slices of banana, oranges, and watermelon, too.
  • Plant other fall-blooming flowers which provide nectar, like asters and goldenrods; there are native species of each in almost all parts of the country.
  • See more nectar plants for monarchs by region

Of course, avoid herbicides such as glyphosate and insecticides such as neonicotinoids, especially on fall-blooming plants. 

Learn more about which native milkweed varieties to plant

2023 Almanac Club