Aug 1, 2018 By Harry Funk staff Writer hfunk@thealmanac.Net 4 min read

As an environmental biologist, Bethel Park resident Roxanne Swan is especially cognizant of the relative preponderance of certain plants.

“I don’t know about you, but when I used to go outside, I would see milkweed everywhere,” she said. “And I don’t really see it quite as often now.”

A common reaction might be, so what? But Swan sets the record straight in her program “Monarchs and Milkweed,” which she presented July 29 at Mt. Lebanon Public Library on behalf of the Audubon Society of Western Pennsylvania.

Milkweed, you see, is the only plant on which the iconic but imperiled monarch butterfly lays its eggs, and so a decline in one is not good news for the other.

The monarch, in turn, is a pollinator insect, essential in the reproductive cycle of most flowering plants. And according to the North American Pollinator Protection Campaign:

“Without the actions of pollinators, agricultural economies, our food supply and surrounding landscapes would collapse.”

Milkweed, though, often falls victim to the application of herbicides and other detrimental practices.

“It’s looked at as a weed and not as a beneficial plant, as we all know now that it is,” Swan explained.

With regard to the monarch, milkweed serves as more than an egg-laying location.

“When they’re adults, they can nectar on many different types of flowering plants,” Swan said about the insect’s feeding process. “But as caterpillars, they can only eat milkweed.”

The utter dependence of the monarch on milkweed has contributed to a steep decline in the insect’s numbers: 80 percent over the past two decades, according to the Center for Biological Diversity, a national nonprofit conservation organization.

The group cites the widespread use of the herbicide Roundup as having “virtually wiped out milkweed plants in Midwestern corn and soybean fields,” which contain crops that are genetically engineered to be resistant to the poison.

A relative lack of milkweed also affects the monarch’s migration, as most of the butterflies east of the Rocky Mountains travel to a small area of Mexico to hibernate each winter.

“Their big cue, when they know it’s time to migrate, is the senescence, or dying back of milkweed. They’re not going to lay their eggs on a plant that’s dying or on its way out,” Swan explained.

Replenishing the quantity of milkweed, though, can be a tricky proposition. Recent efforts locally, for example, included planting a species from Florida.

“That plant lives on much longer in the season, so they were sticking around, laying eggs on that Florida milkweed and not preparing for migration,” Swan said. “We don’t want to put them into a situation where they’re going to be trapped here and not have enough time to migrate.”

Three species of milkweed – common (Asclepias syriaca), Swamp (Asclepias incarnata) and butterflyweed (Asclepias tuberosa) – are typical in Western Pennsylvania, and Swan recommends planting those as contributions toward helping to ensure the survival of the monarch.

“There are a lot of environmental problems out there that we can’t control,” she said. “But planting native plants and encouraging and increasing habitat is definitely something that we can all do.”

With one caveat, though.

“They’re very difficult to grow. It’s one of the hardest plants that we have to grow at the nursery,” Swan said about the plant center, where she serves as coordinator, at the Audubon Society’s Beechwood Farms Nature Reserve in Fox Chapel. “Once it gets established in the ground, it’s pretty easy. So don’t be discouraged. If you want one plant, plant about 20 seeds.”

For more information about the Audubon Society of Western Pennsylvania, visit www.aswp.org.