What Is The Relationship Between Monarch Butterflies And Milkweed?

Monarchs and milkweed–they’re as inseparable as bread and butter, soap and water, pen and paper. So, just what is the relationship between monarch butterflies and milkweed? Do monarchs eat any other plants besides milkweed? What other types of flowers can you plant to attract them to your yard? Keep reading! In this article, we’ll answer all of these questions.

The Relationship Between Monarchs and Milkweed

Monarchs are an iconic and highly recognizable species of butterfly. Unfortunately, their numbers have fallen drastically in recent years, largely due to the eradication of milkweed over much of their range.

So, why is milkweed so important to this king of butterflies?

Not only do monarch larvae feed on milkweed plants, but the two organisms have a symbiotic relationship with each other.

By eating the leaves of the milkweed, monarch caterpillars ingest toxins in the plant that make them poisonous to predators. This toxicity remains even when the caterpillars become adult butterflies, and for this reason, birds and other animals avoid eating them.

In return for this protection from predators, monarchs feed on nectar from milkweed flowers, thereby helping to pollinate them and keeping their species going.

Is Tropical Milkweed Killing Monarchs?

Tropical milkweed is a popular choice for many well-meaning gardeners hoping to attract monarchs to their yard. The adult butterflies love nectaring on the flowers and the larvae seem to prefer tropical over other types of milkweed.

The problem with tropical milkweed is that it isn’t native to the United States. For this reason, it can cause disruptions to the butterfly’s natural behaviors and patterns as well as leave them subject to environmental threats.

Let’s take a closer look at some of the ways tropical milkweed can harm monarchs.

• It discourages migration: Monarchs are famous for their yearly migrations, but tropical milkweed can make them think they’ve arrived at their overwintering home in Mexico long before they have. This milkweed species blooms and stays green right up until the first frost, which can encourage monarchs to stay in the area and reproduce where they are, rather than continuing their journey.

• It increases risk of death by freezing: Because monarchs tend to stay where the tropical milkweed is, and it doesn’t die back until the first freeze, any caterpillars or adult butterflies will likely die along with the milkweed when that first freeze hits. Non-native species begin to die back long before the first freeze, prompting monarchs to head south much sooner.

• It increases risk of parasitic infection: Due to the unnaturally long breeding season tropical milkweed provides, monarchs are at a higher risk of being infected by a parasite known as Ophryocystis elektroscirrha. This parasite slowly kills the caterpillars, leading to diminished numbers of adult butterflies.

Though tropical milkweed is not solely responsible for the decline in monarch butterflies, it does have significant impacts on their life cycle and migration. If you’re hoping to attract monarchs by planting milkweed, it’s best to avoid tropical milkweed and choose a species that is native to your area.  

Can Monarch Butterflies Eat Anything Besides Milkweed?

Milkweed is considered the sole host plant of monarch caterpillars. There is some anecdotal evidence that, if no milkweed is available, they will eat the leaves of various squash plants; but this has not been studied scientifically.

There are about 130 different species of milkweed, so even if one were to go extinct, the monarchs would continue to survive as long as there were other species still available in their area.

That said, at least one study has indicated that female monarchs seem to prefer laying eggs on some types of milkweed over others. Some of the more popular types of milkweed include common milkweed and swamp milkweed. 

Other types of milkweed make excellent nectar plants for adult butterflies but are rarely used as host plants by the caterpillars. One example of this is butterfly weed, which has bright blossoms to attract a host of pollinators but is hardly ever chosen for egg-laying by female monarchs. 

What are the Best Plants to Attract Monarch Butterflies?

If you want to help monarch populations and encourage them to visit your yard, it’s a good idea to plant both host and nectar plants. Monarchs love nectaring on milkweed as well as laying their eggs on it, so you might want to plant various native species of milkweed.

Do some research to find out which milkweed species are native to your area, which species monarchs prefer for host plants, and which species they prefer for nectar.

Adult monarchs also enjoy a variety of other flowers for nectaring. Some of their favorites include:

• Lilacs: These fragrant flowers typically bloom in spring, though some types have repeating cycles that cause them to bloom later in the year as well. Lilacs are a favorite choice of monarchs returning from their overwintering locations.

• Goldenrod: Goldenrod blooms in late summer and early fall, as the migrating butterflies are beginning to fly south. The bright yellow flower clusters are extremely attractive to monarchs and provide an excellent nectar source.

• Butterfly bush: Not to be confused with butterfly weed (which is a type of milkweed), butterfly bush is a flowering shrub that comes in a variety of colors, from white to pink to purple. It is a popular choice for many butterflies, including monarchs, and it blooms well throughout summer and early fall.

• Lantanas: If you don’t have a lot of room in your yard or flower garden, planting a few lantanas may be your best option. These small flowering plants don’t take up a lot of space, but the bright red, orange, and yellow blossoms are loved by monarchs and many other butterflies.

• Zinnias: Zinnias are another great space-saving option, though some varieties can grow fairly large. These annual flowering plants produce blooms in many colors throughout the spring, summer, and fall months, and many kinds of butterflies flock to them. 

Conclusion

Monarch butterflies have a symbiotic relationship with milkweed: their larvae eat the leaves, giving them lifelong toxicity to predators, and in return, the adult butterflies pollinate the milkweed. Though milkweed is the only recognized host plant of monarch caterpillars, adult monarchs enjoy nectaring from a variety of different flowers.