The monarch lifecycle is dependent on milkweed. The butterflies lay eggs only on milkweed plants, and those eggs then hatch into caterpillars that feed on the milkweed, Bryerton said. The milkweed also has protective qualities for the butterflies, because the toxins they acquire from eating the plant make them poisonous to many of their potential predators.
Unfortunately, the milkweed population across the United States has dropped significantly, with more than 860 million stems lost nationwide in the past decade, according to the U.S. Geological Survey. This loss of monarch habitat has also caused the monarch population to drop.
This loss of monarch habitat is one of the main contributing factors to a significant and troubling drop in the monarch population, as much as 90 percent over the past 20 years, according to the Illinois Department of Natural Resources (IDNR).
Although monarchs are not listed as an endangered species, with such a devastating drop in the monarch population, efforts are underway nationwide to help address the decline. One of the primary efforts is to replenish the supply of milkweed in areas where the butterflies nest.
“Milkweed plants have become more scarce as we have gotten better at eliminating weeds in general from all types of areas, including farms and right of ways,” Bryerton said. “Also, as we convert more fields into development, there are fewer places for milkweed to grow.”
In some areas, garden clubs, ecological groups and government agencies having been giving away milkweed seeds in the hopes people will plant them to help boost the monarch population. In fact, visitors to the Forest Preserve District’s Plum Creek Nature Center can get free milkweed seeds for planting in their own yards.
Other efforts include attempting to restore milkweed along ditches and rights of way. Some states have also planted milkweed along highways where they do not mow to help increase milkweed stems, Bryerton said.
The U.S. Geological Study estimates as many as 1.8 billion additional milkweed plants may be necessary to return the monarch population to a sustainable size.
While a large-scale effort is needed, including restoring milkweed in agricultural areas, you can help at home too by planting milkweed in your own yard and garden.
“The cool part is if you plant milkweed in your yard, you may be able to watch the entire process of butterfly development,” Bryerton said. “The butterflies will lay eggs on the plants and you can watch the caterpillars develop into a pupa.”
Many species of milkweed are native to Will County and will grow well here with little extra care, he said. “They are designed to tolerate our weather and soil conditions and so grow well here.”
Among the milkweed species to plant in our area are common milkweed, prairie milkweed, swamp milkweed, purple milkweed, butterflyweed and whorled milkweed. The milkweed plants that are native to Illinois are not necessarily something people will find at local nurseries and garden centers, but you can order them online or purchase them at local plant sales.
“The butterflies can smell the plant from a bit of a way off and will be drawn to it,” Bryerton said. “Once they land on it, they will confirm that is indeed milkweed and lay eggs if it is a milkweed plant.”
He said the pollinator garden they maintain at Plum Creek Nature Center includes milkweed among other plants planted with the intention of attracting pollinating birds and insects. The garden was revamped last year, and they added a swamp milkweed plant in one corner.
“We had close to 30 caterpillars on this plant,” he said. “For some reason, the butterflies found this right away and liked it a lot. We were able to watch the adults lay eggs on this plant.”
In addition to planting milkweed to sustain monarchs during the summer, the University of Illinois Extension reports that planting more fall blooming perennials such as liatris, Joe Pye weed, black-eyed Susan, aster, coneflower and downy sunflower in gardens will also provide resources for the butterflies before their long journey back to Mexico.