Monarchs & Milkweed

When we think about monarch butterflies, we often picture their gorgeous color, their amazing life cycle and their incredible and mysterious migration. However, what we often overlook is the real star of the show: milkweed. Without milkweed, monarchs cannot become that beautiful orange and black butterfly, cannot complete that amazing life cycle, and cannot embark on that amazing journey.

Milkweed is not a single species of plant, it is a collective name for many species of milkweed plants in the genus Asclepias. There are almost 100 species of milkweed in North America, all differing in one way or another. However, almost every one (with the exception of butterfly weed) has something in common: the toxic, white, milky sap that protects monarch caterpillars when they consume it along with the leaves. Since plants in the Asclepias genus are considered a monarch's "larval host plant," it is imperative that we protect these plants in order to help bring back our rapidly declining monarch populations. See how to help milkweed and monarchs below.

Milkweed plants feed caterpillars throughout all five instar stages and is an excellent source of nectar for adult monarch butterflies, not only during the season, but also during migration. In short, milkweed is absolutely critical.

Monarchs and Milkweed Gallery and Video

Female Laying Egg on Common Milkweed

Female monarch butterflies lay their eggs on milkweed plants, typically on the bottom of the leaf. If they lay on another non-milkweed plant, the caterpillar willl die.

Monarch Egg on Underside of Common Milkweed Leaf

This tiny monarch egg has been laid on the underside of a milkweed leaf. It will take 3-6 days (depending on temperature) before it hatches, and when it does, its first meal will be its egg shell followed by an exclusive diet of milkweed leaves.

Male Monarch on Common Milkweed

Females may lay eggs on milkweed, but males, like this one, are often seen nectaring on milkweed species. Milkweed provides nectar for numerous pollinators, but monarchs are completely reliant on it for completing their life cycle.

Female Monarch Nectaring on Butterfly Weed

This monarch butterfly is nectaring on butterfly weed (Asclepias tuberosa). Milkweed is necessary for completing the life cycle. Late blooming species are also an excellent food source for monarchs during migration.

Monarch Caterpillar Eating Butterfly Weed Flowers

Monarch caterpillars rely on milkweed to survive. This caterpillar is feeding on butterfly weed flowers. Butterfly weed does not have the milky white latex, or sap, found in other milkweed plants. The sap is clear and less toxic than other species.

Video of Monarch Caterpillar Eating a Butterfly Weed Pod

Monarch caterpillars typically eat leaves throughout their larval stage. Occasionally they will eat pods and flowers of butterfly weed, as seen in this video.

How to Help Monarchs

First, a note about rearing monarch butterflies... Research has shown that rearing monarchs with the hope of saving the species is accomplishing quite the opposite. It has been proven that rearing monarchs spreads disease and parasites (such as OE) among the captive monarchs, but can also be spread to wild populations. Rearing monarchs can also make them unfit and significantly hamper their migration, which is one of the things that makes them so epically cool, right? For monarchs' sake, captive rearing should only be done by those who are properly trained. Teachers who collect one or two eggs for a monarch curriculum, apparently does not harm the population, but this practice may change if monarchs are listed by the U.S. Fish and Wildlife Service as "Endangered" in the near future.

The better option is take a field trip to a milkweed patch and try to find eggs and caterpillars yourself. Then watch as they grow and change! You can also participate in community science projects that will not only teach you how to collect data, but will actually help monarchs!

Please remember that you need a Scientific Collecting Permit (SCP) issued by the California Department of Fish and Wildlife to handle monarchs in any life cycle stage in California.

You can learn about the monarch life cycle here.

1) STOP USING PESTICIDES! Pesticides are a huge problem, however, damage caused by them can be reversed, simply by ceasing to use them right now. Researchers from The Xerces Society of Invertebrate Conservation (Xerces) have conducted research and sampled plants both in the wild and in nurseries. Their findings are startling and we, as humans, should take notice. Xerces biologists said:

" Pesticides were detected in every sample, even at sites with little or no pesticide use based on information from landowners."

Pesticides are often used by farmers, property managers, gardeners and homeowners to kill milkweed plants or other species they feel are a "nuisance." Keep in mind, though, that no milkweed = no monarchs.

For more information about milkweed and pesticides, please check out:

Pesticide Contamination of Milkweeds Across the Agricultural, Urban, and Open Spaces of Low-Elevation Northern California

How Pesticide Sampling Can Help Restore Imperiled Western Monarchs

2) Plant milkweed native to your region. Never plant tropical, or Mexican milkweed (Asclepias curassavica). You can find your region's native milkweed species by visiting:

Xerces Milkweed Seed Finder

Grow Milkweed Plants

Milkweed & Wildflower Vendors

3) Plant a pollinator garden with native nectar plants for adult butterflies. It is important to supply monarchs with flowering plants in the spring as well as in the fall. Monarchs need a food source during their fall migration to get them to their overwintering grounds, therefore, keep in mind those fall bloomers when you plant your pollinator garden. Other pollinators and birds will benefit as well, so you will have many unique visitors to your garden along with monarchs! If you are unable to find pesticide-free, (not organic!) at your local nursery, ask them if they will consider carrying them. If enough people request them, and there is high enough demand for them, they will have to carry them. You can also find native flowering plants that are just right for your garden by visiting:

NWF Native Plant Finder

For region-specific collections of publications, native plant and seed suppliers, and other resources to aid in planning, establishing, restoring, and maintaining pollinator habitat—as well as materials to help you learn about the various invertebrates you might encounter check out the Xerces Pollinator Conservation Resource Center!

Pollinator Conservation Resource Center