Is the monarch butterfly ready for its moment?

URI researchers would like to see the monarch get its due

Kristen Curry

Despite weighing half a gram each, between August and October, monarch butterflies
will travel up to 3,000 miles from the U.S. and Canada to the mountains of Mexico,
sipping flower nectar as fuel for their journey. (URI Photos / Casey Johnson)

As summer progresses and travelers embark on trips to destinations near and far, Steven Alm and Casey Johnson in the University of Rhode Island plant sciences and entomology department would like to remind New Englanders of another late summer and fall traveler — the monarch butterfly.

Between August and October, monarch butterflies travel up to 3,000 miles from the U.S. and Canada to overwintering grounds in the mountains of Mexico.

Monarchs are first seen in Rhode Island in June; their numbers increase through late summer and into fall when secondary generations begin their journey southward. The orange and black butterflies can be spotted in gardens and fields, especially those with lots of native milkweeds and flowers.

LEAVE BUTTERFLY BABIES ALONE! Researchers at URI say that homegrown
 butterfly gardens help. Even a single potted plant outside the front
door has the potential to provide food for beneficial insects. (Casey Johnson)

Their flight is fueled by flower nectar, so they need plenty of food sources to alight on: butterfly weed, common and swamp milkweed, red clover, blazing stars, bee balm, native thistles, purple coneflowers, asters, goldenrods, New York ironweed, Joe-pye weed, and sweet pepperbush all provide abundant nourishment for the long journey.

The monarch is one of hundreds of species of butterflies and moths that call Rhode Island home for at least some of the year. 

Some are more common than others, but the monarch is one species with documented drastic declines. Many of Rhode Island’s local insects, including moths and butterflies, benefit from Rhode Islanders planting more native plants, removing invasive species, reducing pesticide use, leaving the leaves for overwintering insects, and advocating for their conservation.

The monarch weighs about half a gram, less than the weight of a paper clip, yet can fly thousands of miles sipping nectar as fuel for the journey.

Milkweed comes in a variety of species and is the only host plant for monarch 
caterpillars (larvae) to survive on. Butterfly weed (shown) is
 one attractive variety. (Catherine Scott)

Alm and Johnson hope to help cultivate support and awareness to help this unique creature, similar to the support for other threatened species like the bald eagle have seen. A professor at URI and keeper of the University’s historic Insect Collection, Alm is concerned about the insect loss he’s witnessed over his career.

During the last three decades, the eastern migratory monarch butterfly population has decreased by more than 80%, according to the World Wildlife Fund. In 2021, the International Union for the Conservation of Nature listed the population as endangered which was changed to vulnerable in December 2023.

Regardless of classification, Alm and Johnson call the monarch a unique species worth looking out for.

“It’s a special animal,” he says.

Increasing plant and animal literacy is one way for gardeners and environmental supporters to help improve the insect environment, one plant at a time. And the gardens themselves are key.

“Butterfly gardens help,” Johnson says. “We need more.”

Alm and Johnson say one of the best ways to help support monarchs is to increase milkweed, an important food source which helps protect the larvae and adults from predators. Monarch larvae consume toxic substances in milkweed as they feed on its foliage. The toxins are transferred into the adult butterflies, which helps to protect them from predators such as birds.

To help backyard and front-step gardeners be good hosts for the monarch and other butterflies, Alm and Johnson answered some questions. (They are also available for interviewing by media in the University’s butterfly gardens.)

Why is milkweed so important for the monarch butterfly’s journey?

Milkweed gets its name from the sticky white liquid exuded from its leaves when damaged. It is the only food plant for monarch larvae.

Generations of monarchs rely on nourishment from milkweed and other plant species to migrate between New England and the Sierra Madre mountains of Mexico. After resting there from November through February, the same butterflies migrate back to the U.S. to lay eggs on milkweed in the southern states. Monarch butterflies typically live from 2 to 6 weeks, however, the last generation of the year can live up to 8 or 9 months.

What has harmed monarchs?

Residential and commercial development, forest removal in the butterfly’s overwintering grounds in Mexico, agricultural intensification, fire, climate change, and pesticides that remove milkweed and floral nectar sources. Severe weather also poses a challenge.

What would you like the public to know about the monarch and how home gardeners can help them?

• Plant a 4-by-4 foot area of any of the plants listed above that you can accommodate; however, even a few plants in a window box or in pots on steps can help. 
• The milkweed provides a home for monarch eggs and larvae and the flowering plants provide adult monarchs with nectar for their migration flights. 
• Volunteer with local land trusts that encourage the planting of native plants in one’s community. 
• Keep in mind that if you plant milkweeds and other native plants, you want caterpillars and other native insects to eat your plants. 
• Purchase milkweeds from nurseries that don’t use pesticides, or purchase (or save) seeds, store them in your freezer or outside for the winter and plant them in the spring. 
• If your garden is tight for space and you don’t want to plant native milkweed that would spread, try butterfly milkweed (Asclepias tuberosa) or swamp milkweed (Asclepias incarnata). 
• Avoid planting tropical milkweeds or other milkweeds not native to your area.

What else can people do to help monarch butterflies on their journey?

• Conserve and plant milkweed for adults to lay their eggs on and larvae to develop on. 
• Remove black and pale swallow-worts, invasive weeds that monarch butterflies will confuse with milkweeds; monarchs are unable to survive on these invasive plants and will die. 
• Remove these toxic weeds from the roots as soon as they are found and monitor for new growth.

What should Rhode Islanders look for at the start of the butterfly migration this season?

Look for caterpillars on milkweed leaves, but don’t disturb them; leave them there to develop into adults. Adult butterflies are seen in Rhode Island from August through October.

Notice the adults on the wing and notice how they “float” and what flowers they are attracted to. Plant more of those flowers in the future.

Let the pods develop on the milkweed plants until they break open and float their seeds via the “parachutes” attached to each seed. This “parachute” material is six times more buoyant than cork and five times warmer than wool. Large quantities of milkweed were grown for use as stuffing in pillows and lifejackets during World War II, in fact. Milkweed seeds will mature on the plant and are ready to harvest once the pods break open in September or October.

Pick up Monarchs and Milkweed by Anurag Agrawal, a very readable book on this incredible migrating butterfly and its poisonous host plant.

Contemplate the possibility of losing this magnificent insect for future generations to enjoy and marvel at. The monarch is another sentinel (canary in a coal mine) that is warning us that all is not right with its world and ours as well. Do what you can to prevent the monarch’s extinction!

Alm and Johnson field inquiries about butterflies, bees and other insects in the University’s entomology department. Homeowners with questions about plants, insects, plant pests and diseases, wildlife, landscape management and more are encouraged to contact the URI Gardening and Environmental Hotline by phone at 401-874-4836 (M–F, 10–2 p.m.) or via email at gardener@uri.edu anytime. See URI Cooperative Extension or email coopext@uri.edu to join their email list and receive notifications about events, resources and programs.