Milkweed and Monarchs

An orange and black butterfly with white spots stands perched on a human finger.
Monarch butterflies are dependent on a plant called milkweed.

NPS Photo / Bryan Maul

Wide pointed oval green leaves point upward with small yellow and white five petal flowers clustered within.
Pictured is a broadleaf milkweed (Asclepias latifolia) in flower.

NPS Photo


Milkweed is an integral part in the monarch butterfly’s life cycle. Asclepias is the genus for milkweed. Asclepias subverticillata, or horsetail milkweed, and Asclepias asperula, or spider milkweed, are the two most common milkweed plants on the rims of Grand Canyon National Park. Asclepias latifolia, or broadleaf milkweed, is common at lower elevations in Grand Canyon near the river.

This website helps identify some of the most common native species of milkweed and lists the states you can find them in!

An orange and black butterfly with white spots stands on the tops of a cluster of purple flowers.

NPS Photo


Monarch butterflies (Danaus plexippus) are an important and unique invertebrate species, spanning across North America. They live in prairies, meadows, grasslands, roadsides, and more. The markings on monarch wings are unique and easily recognized by predators as a warning. Their markings are interpreted by predators similarly to how humans understand a skull and cross-bones sign, signaling poison and danger.

Female monarchs lay their eggs under milkweed leaves, and once the caterpillars have eaten through their egg, they begin to feed on the toxic plant. These chemicals stay in their bodies as they mature into butterflies. The chemicals act as a deterrent, making the monarchs taste bad to their predators, which then encourages predators to avoid butterflies with these distinct markings on their wings.

Monarchs can be found in parks all over the country!


Fun Fact!

Monarch caterpillars are known to eat 200 times their body weight in milkweed!


Monarch Caterpillar Transformation to a Chrysalis

Two white, black, and yellow striped caterpillars balance on thin green leaves. Two white, black, and yellow striped caterpillars balance on thin green leaves.

Left image
The monarch caterpillar will eat milkweed leaves until it is ready to form a chrysalis.
Credit: NPS Photo

Right image
The monarch butterfly will ultimately emerge from this chrysalis.
Credit: NPS Photo

A black and orange butterfly stands on yellow white flowers amongst skinny green vertical leaves.
A monarch butterfly on a horsetail milkweed (Asclepias suberticillata) flower.

NPS Photo / Melissa Stellar

Lifespan of a Monarch

Western American Monarchs generally only live a few weeks, but, just like clockwork, in late summer and early fall there is a new generation born for migration. They travel hundreds of miles over several months to make this migration south, towards southern California and Mexico. The migration happens because they cannot survive the cold winter temperatures in the northern states.

Learn more about monarch migration.

Monarchs as an Endangered Species

Monarch butterfly populations have been in a severe decline since the 1980s, when there were over 4.5 million individuals. As of 2019, there were fewer than 30,000 individuals. Some ways that monarchs are being negatively impacted include: climate change, milkweed population decline, and winter habitat loss. Concerned by the urgent need for action, in 2020, the United States Fish & Wildlife Service (USFWS) placed monarchs as a candidate species under the Endangered Species Act.


Monarchs at Grand Canyon

Grand Canyon National Park and the Colorado River that runs through it occur along a critical monarch butterfly migration path, and are the home of host plants that are essential for monarch survival, such as milkweed and other nectar-rich species. Grand Canyon is working to convert degraded land into restored monarch habitat by establishing pollinator gardens. Make sure to visit Pima Point, a beautiful stop along Hermit Rd., in the near future to check out a newly installed pollinator garden, full of milkweed and nectar-rich plants!

A woman in a green hat stands facing a yellow flowered bush with a net overtop of the plant.
A Park Ranger attempts to catch a monarch butterfly out in the field.

NPS Photo

Get Involved!

Scientists at Grand Canyon and across the Southwest also work to safely catch, tag, and document monarchs so that communities across the country can identify monarch migration patterns and learn more about the current population status. You can get involved at home by joining community science opportunities in your region! Go to Monarch Joint Venture to find a community science opportunity near you.

A human hand carefully holds a monarch butterfly, while a scientists takes data in the background.
A monarch butterfly in someone’s hand as their counterpart works to write down tag information. The net used to safely capture the monarch is in the frame.

NPS Photo

It is important to do everything we can to save this species! Some action items you can take at home are:

Last updated: September 8, 2021

Contact the Park

Mailing Address:

PO Box 129
Grand Canyon , AZ 86023



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