Skip to content
Express to
your inbox

Sign up for the High Line newsletter for the latest updates, stories, events & more.

Loading...
Please enter a valid email address!
Thanks for signing up, we'll be in touch soon!
Photo by Flickr user WolfSilverOak

Protecting the magic of monarch butterflies

November 8, 2023

Monarch butterflies are a welcome sight in the garden, where they pollinate flowers while sipping nectar. From their bold coloring to their lengthy annual migration, monarch butterflies are one of North America’s most iconic insects. This unique butterfly is the only butterfly in the world known to make a two-way migration, with the cycle beginning in the northern US and Canada; winter hibernation taking place in warmer locales in California, Florida, or Mexico, depending on their ancestral coast; and then looping back up to start all over again each year.

They are also an unfortunate harbinger of environmental issues that are impacting other pollinators and insects. Climate change, habitat loss, pesticides, and more have created dramatic decreases in the monarch population—a startling decline of more than 80% over the last 20 years. While monarchs have not yet been added to the Endangered Species List in the US, they are slated to be added in early 2024.

The monarch life cycle in four acts
Monarch butterflies go through four different stages in their individual life cycles and there are four separate generations of monarchs each calendar year. Individual monarchs start out as eggs, as all butterflies do. Female monarchs lay their eggs on the underside of leaves on milkweed plants, the only plant that young monarchs can eat. Milkweed leaves are generally not appetizing to insects and animals; their leaves contain toxins called cardenolides that at best just taste gross and at worst can cause heart problems for those who dare to ingest them. Monarchs, and a handful of other insects like them who can tolerate—and even thrive on—milkweed have evolved over time to be unfazed by the plant’s toxins. What’s more, monarch caterpillars and their adult versions retain some of these toxic chemicals, making them taste bad and causing digestive issues for predators who may eat them, which teaches animals to associate their bold colors with a “do not eat” warning.

Monarchs born in the spring and early summer only live 2 – 6 weeks in total, from hatching to mating and laying eggs for the next generation. The last generation of the late summer or early fall is the most unique and longest-lived—on the east coast, these butterflies make the 1,000 – 2,800-mile migration to Florida or Mexico where they will hibernate over the winter and return north in early spring to start the cycle all over again.

The movement to save monarchs
As its common name suggests, milkweed is considered a weed in most parts of North America, popping up in wild areas, between cultivated crops, on roadsides, and even in small patches of green in urban areas. However, this genus (a scientific taxonomic group) of plants—of which there are around 100 species native to North America—is key to the survival of monarch butterflies, as they are the only host plants for monarch caterpillars.

Habitat loss for monarch butterflies is driving their population decreases, both in the US and where they overwinter in Mexico. Notably on the US side, a recent increase in the use of herbicides that kill milkweeds—and other weeds—on agricultural land has decreased food sources for young monarchs. Land development, wildfires, and climate change-related shifts in temperature have also had huge impacts on the number of milkweed plants available.

Conservation groups and concerned citizens alike are rallying to increase awareness of—and action on—the milkweed shortage. As Eric Lee-Mäder, author of The Milkweed Lands: An Epic Story of One Plant, Its Nature and Ecology, said in a recent New York Times article, “The milkweed is a displaced citizen in its own land… Milkweeds, at least the North American ones, are like so many other meadow and grassland species. They’re both dependent upon us and also subject to the various indignities of coexisting with us.” Thankfully, grassroots efforts are taking place around the country to help conserve critical habitat for monarch caterpillars, including in our own backyard in New York City.

High Line weeds—with a purpose
The High Line is home to many native plants—with more than 150 species of New York City natives in the park that provide habitat and food sources for native pollinators, birds, and other wildlife. Contrasted with non-native or exotic ornamental plants, native plants are key resources for native wildlife, particularly for species that have niche relationships, like monarchs.

We’re proud to grow five species of native milkweeds, which you’ll find in abundance along the length of the park. Learn more about our milkweed species below.

Swamp milkweed

Swamp milkweed
Asclepias incarnata ssp. pulchra
This moisture-loving plant is native to the central and eastern US. You’ll find it growing wild near ponds, streams, and low-lying areas. It’s one of monarchs’ preferred milkweeds for eating in their caterpillar stage.

Butterfly on butterfly milkweed

Butterfly milkweed
Asclepias tuberosa
Also known as butterfly weed, this milkweed got its name for its attractiveness to butterflies who love its bloom color and copious amounts of nectar. Fun fact: butterflies are most attracted to orange—like butterfly milkweed—red, yellow, pink, and purple blooms.

purple milkweed

Purple milkweed
Asclepias purpurascens
This milkweed is native to the eastern half of the US. It is considered rare in New York State and endangered in other states. It has especially fragrant blooms that attract all kinds of pollinators, including long-tongued bees, hummingbirds, and butterflies.

Whorled milkweed

Whorled milkweed
Asclepias verticillata
This dryland prairie native is found throughout the Midwest and Northeast. It has narrow leaves that whorl around the upright stems that can slowly spread through rhizomes. Flowers are delicate white clusters of small flowers that attract a variety of pollinators, especially small bees.

common milkweed

Common milkweed
Asclepias syriaca
One of the most common milkweeds found throughout the northeast (hence its common name). This coarse perennial grows up to three feet tall in fields and open woods and along roadside and railroad tracks. The pinkish flowers are slightly fragrant and develop into large warty seed pods that split open in the fall to let the silky seeds disperse in the wind or on animal fur.

Illustration of a caterpillar and butterfly on butterfly milkweed
Adopt a butterfly milkweed

Support milkweed-munching monarchs and pollinators of all stripes by adopting a butterfly milkweed today.

Adopt a plant

 

 

 

More resources for learning

New York Times, To Save Monarch Butterflies, They Had to Silence the Mowers, October 14, 2023.

New York Times, “If You Plant Milkweed, They Will Come. (And Not Just the Butterflies.),” October 25, 2023.

Xerces Society guides to milkweed: find native milkweeds where you live, tips for growing, info on harvesting seeds, and more.

All about native plants on the High Line

 

Support

Lead support for Horticulture on the High Line is provided by Amanda M. Burden.

Program support for Horticulture on the High Line is provided by Greenacre Foundation.

Categories: