A surprising MoBot discovery is saving Mead’s milkweed
Nearly 100 miles south of St. Louis in Taum Sauk Mountain State Park grows a rare, yellow-flowering plant called Mead’s milkweed. The perennial plant of the tallgrass prairie beloved by Monarch butterflies is native to Missouri and today is primarily found in the Show-Me State and eastern Kansas.
Since 1988, Mead’s milkweed has been listed as a threatened species. But researchers at the Missouri Botanical Garden have made a breakthrough in understanding the plant’s propagation problems. And, if conservation geneticist Christy Edwards gets her way, her research will give the species a fighting chance at survival.
“I think we're gonna hopefully get a kind of a burst of reproduction in the species,” said Edwards, who works at MoBOT’s Center for Conservation and Sustainable Development.
Along with scientists Matthew Albrecht and Shannon Skarha, Edwards discovered that previous conservation practices weren’t working. Mainly, Missouri Department of Conservation officials were transplanting the milkweed to increase genetic diversity.
It’s an onerous process, and state conservation officials asked Edwards whether they were on the right track. Her research revealed that genetic diversity was not the problem — but rather that most remaining pockets of prairie simply didn’t have enough flowering plants.
“When we looked at the relationship between genetic diversity and reproductive success, there was no relationship at all. It was really surprising,” Edwards said.
“If you have enough flowering individuals in the population, you get reproduction occurring,” she continued. “And that number is about 50 individuals flowering at once.”
That’s achieved partly by the old conservation strategy of adding Mead’s milkweed to spots where they already exist, but another key is better use of prescribed burns. Previously, land managers might burn a small area, which triggers the affected plants to burn. But if too small an area was selected for burning, not enough milkweed was blooming at once.
“People have been burning one plot one year and a different plot the next year, so they were never getting 50 individuals flowering at once,” she explained. With greater awareness of milkweed’s need for numbers, those tactics can change.
Edwards said conservation officials are now spreading the word across the state. She said, “People are excited about the results.”
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