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U.S. Forest Service

Plant of the Week

Map of the United States showing states. States are colored green where the species may be found.Mead’s Milkweed (Asclepias meadii) range map. USDA PLANTS Database.

Mead’s Milkweed (Asclepias meadii) close up.Mead’s Milkweed (Asclepias meadii) close-up view.

Spiranthes diluvialisMead’s Milkweed (Asclepias meadii) plant and stem.

Mead’s Milkweed (Asclepias meadii)

By Christopher David Benda

Mead’s Milkweed is a rare perennial plant in the Milkweed family (Asclepiadaceae). The genus name “Asclepias” refers to the Greek god of medicine Asklepios, while “meadii” refers to this species being named in honor of Dr. Samuel Mead, the original collector of this species in Illinois in 1843. Little did Dr. Mead know that a century later, this species would be extirpated throughout most of its range.

The current rarity of the species can be explained by several factors. Most of the prairie habitat that harbored this species has been converted to agriculture. This species is slow growing and can take four years to flower. Long-lived species tend to produce fewer offspring than short-lived species and annuals. Little is known about the pollination of this species, but the scarcity of populations leads to low visitation by insects, although bees having been observed on flowers. Combined with frequent mowing in many of the areas where this species remains, this plant rarely produces seed, and when it does, it is often unviable due to inadequate gene flow. Thus, this species often reproduces vegetatively and many populations exist only of clones.

Once widespread across the virgin tallgrass prairies of the Midwest, this species is now extirpated or rare across most of its range, leading to it being listed as federally threatened. Fire is essential to the persistence of this species. It remains in high quality prairie habitats and railroad right-of-ways in Iowa, Illinois, Missouri, and eastern Kansas.

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