Mother That Milkweed

Pamela Smith
By  Pamela Smith , Crops Technology Editor
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Monarchs are partial to common milkweed for egg laying. The leaves are food sources for the caterpillars, and the flowers become nectar sources for adult butterflies, Image by Pamela Smith

Encouraging weeds to grow isn’t something Andy Herring generally works to achieve. However, last year, the North Carolina farmer joined in a national effort to plant milkweed to support monarch butterflies along their migration path. That experience taught him the plant can be a bit finicky to establish.

He purposefully chose a strip of land that did not butt right up against production cropland. “Milkweed is still sensitive to most herbicides,” he notes.

Good butterfly habitat is an area that can be left somewhat wild. Herring picked a sunny location with a nearby ditch bank and wooded area to provide additional habitat diversity.

Most grazing animals learn to avoid milkweeds, but plot placement is important. Milkweeds contain various amounts of cardenolides (cardiac glycosides), which can be toxic to livestock if consumed in large quantities.

Herring started with milkweed starter plants provided through BASF’s Monarch Challenge program. Launched last year, the initiative prompted more than 500 growers and farm families to plant 9,000 milkweed stems. The company is expanding the program in 2018.

More than 80 species of milkweed exist in the United States, but all are not native to the monarch migration path. Laura Vance, BASF’s biology project leader for soil management, suggests first learning what species support egg laying and larval development for the area being planted. Then, select other milkweed species, as well as other flowering plants, to provide nectar sources for adult monarchs.

Start with a relatively clean seedbed. “Grasses, in particular, can be competitive,” Vance says. Plant seedlings in the spring, dig a decent size hole and mix in a bit of potting soil to help establishment.

She also suggests keeping the milkweed plants watered during the first year. “I know it may seem silly to baby a weed, but we really want to make sure it takes off that first year,” she says. Established milkweed spreads by both seed and underground rhizomes.

For More Information:

University of Minnesota Monarch Lab

BASF’s Monarch Challenge Program

Monarch Migration Tracking

Iowa State University Monarch Practices


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