By Brittnay Haag
Imagine eating only one type of food your entire life. Your survival depends entirely on being able to find this food. It is the challenge monarch butterflies, Danaus plexippus, face every day as landscapes change nationwide and fewer native plants are available. But home gardeners can help.
Along with other insects, monarch butterfly populations have been declining for decades. This week, the non-governmental organization International Union for the Conservation of Nature listed a subspecies of monarch butterflies as endangered. The U.S. government maintains its own endangered species list which entitles species to federal protection under the Endangered Species Act. Monarch butterflies were denied federal endangered status in 2020.
The monarch caterpillar feeds exclusively on milkweed, Asclepias sp., plants said Brittnay Haag, University of Illinois Extension horticulture educator. “It is a unique relationship,” Haag said. “If no milkweeds are growing in the landscape, no monarch butterflies are flying around the garden.”
Females typically lay their eggs on milkweed leaves to ensure larvae have an immediate food source once they hatch so they have enough energy to transform into a chrysalis. Monarchs have adapted to eat the toxic compounds found in milkweed, cardiac glycosides, which deters birds and small mammals from eating them as adult butterflies. Once an adult monarch butterfly emerges, they will visit flowering plants, including milkweed, for nectar.
Illinois is home to 22 species of milkweed and the state butterfly is, you guessed it, the monarch. “All of these grow in a variety of habitats that easily can be replicated in your own backyard, allowing you to grow the plants that support monarchs,” Haag said.
Milkweeds are a great native plant for the home garden with colorful blooms to support local wildlife. These herbaceous perennials flower in Spring and Summer. Milkweed flowers have high levels of nectar and are a favorite food source for pollinators. Flower colors vary from species to species but can be pink, purple, red, white, green, or orange. Mature flowers turn into pods of seeds that are attached to white, fluffy, floss, which is easily dispersed throughout the landscapes by the wind.
Common milkweed, Asclepias syriaca, is a weedy species that is unwanted by many gardeners and farmers.
“Thankfully, there are gorgeous alternatives to this milkweed species which support the monarch in a variety of habitats,” Haag said.
A huge patch of milkweed is not necessary to benefit the monarchs, a small patch can be a great resource. Consider planting multiple species for season-long support of the monarch because each species has a distinct phenology and bloom time.
Butterfly milkweed, Asclepias tuberosa, has striking orange flowers that make it an ornamental garden favorite, many gardeners do not even realize it is milkweed. It blooms from May through September, growing two to three feet tall. It grows best in full sun and well-drained soils.
Prairie milkweed, Asclepias sulvantii, commonly called Sullivant’s milkweed, is found in moist to wet prairies in Illinois. It is often mistaken for common milkweed, but it has smooth, succulent-like leaves and is not aggressive in the landscape. It makes a great addition to any perennial flower garden with its large leaves, reaching three to four feet tall.
Swamp milkweed, Asclepias incarnata, is found natively growing in swampy areas, wet ditches, and meadows throughout Illinois. The gorgeous pink blooms appear June through August, on top five-foot lance-shaped foliage. This plant prefers full sun and moist, well-drained soils.
Poke milkweed, Asclepias exaltata, grows best in shade, or partial sun, in moist, well-drained soils. It can reach 2 to 6 feet tall, depending on the growing conditions. The white, drooping blooms appear from June through August.
Whorled milkweed, Asclepias verticillate, has whorled, linear leaves that grow best in full sun and moderate to dry conditions. It blooms later than most milkweed, July through September. It creates 1 to 2-foot-tall drifts of fine, delicately textured foliage.
Explore more ways to support pollinators at extension.illinois.edu/insects/pollinators. Or, connect with your local Illinois Extension or county office at go.illinois.edu/ExtensionOffice.
Brittnay Haag is a horticulture educator at the University of Illinois Extension.
—University of Illinois Extension