Asclepias verticillata

Asclepias verticillata
Conservation status
Secure  (NatureServe)
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Asterids
Order:	Gentianales
Family:	Apocynaceae
Genus:	Asclepias
Species:	A. verticillata
Binomial name
Asclepias verticillata L.

Asclepias verticillata, the whorled milkweed, eastern whorled milkweed, or horsetail milkweed, is a species of milkweed native to most of eastern North America and parts of western Canada and the United States. ^[1]

Description

This is a perennial herb with a single stem 6 inches to 3 feet tall. The very narrow, linear leaves are arranged in whorls of 4–6 with short internodes. The inflorescence is an umbel of 7–20 greenish white flowers. ^{[2] [3]} The Latin specific epithet verticillata is in reference to the leaves appearing in whorls. ^[4]

Ecology

Habitat

A. verticillata is native to habitats such as loblolly pine plantations, upland pine-hardwood communities, and glades, among others. ^[5] This species has also been found along roadsides.

It is limited to primarily sandy soils, and requires light levels between full sunlight and partial shade. It can grow in either xeric or moist conditions. ^[6]

Phenology

This species' flowers are fragrant and bloom between June and September, with peak inflorescence occurring in August. It has been found to fruit within the same period. ^[7]

Fire Ecology

As A. verticillata is native to several habitat types that experience a fire regime, many individuals are subject to repeated annuals burns. This species has been found to persist through burns, and increase in frequency as a response to repeated prescribed fires. ^[8]

Pollination, herbivory, and toxicology

This species can reproduce vegetatively and does not depend on pollinators, but it does produce some nectar, mostly in the early evening hours. Insect visitors to the plant include wasps, honeybees, and lepidopterans such as moths and the cabbage white. ^[9] Like other milkweed species, this plant is a host plant for the monarch butterfly whose caterpillars feed on the leaves.

The plant is toxic to livestock. ^[3]

Uses

It was used as a medicinal plant by Native American peoples. The Choctaw used it to treat snakebite, the Lakota and Hopi used it to increase breast milk in nursing mothers, and the Navajo used it for nose and throat problems. ^[10]

References

1. "Asclepias verticillata". Germplasm Resources Information Network . Agricultural Research Service, United States Department of Agriculture . Retrieved 12 January 2018.
2. Hilty, John (2020). "Whorled Milkweed (Asclepias verticillata)". Illinois Wildflowers.
3. "Asclepias verticillata". Native Plant Database. Lady Bird Johnson Wildflower Center, University of Texas at Austin.
4. "Asclepias verticillata - Plant Finder". www.missouribotanicalgarden.org. Retrieved 2022-01-12.
5. Hover, E. I. and T. B. Bragg (1981). "Effect of season of burning and mowing on an eastern Nebraska Stipa-Andropogon prairie." American Midland Naturalist 105: 13-18.
6. Weakley, A.S. 2020. Flora of the Southeastern United States. Edition of 20 October 2020. University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
7. Nelson, G. PanFlora: Plant data for the eastern United States with emphasis on the Southeastern Coastal Plains, Florida, and the Florida Panhandle. www.gilnelson.com/PanFlora/ Accessed: 11 July 2025
8. Glitzenstein, Jeff S.; Streng, Donna R.; Masters, Ronald E.; Robertson, Kevin M.; Hermann, Sharon M. (January 2012). "Fire-frequency effects on vegetation in north Florida pinelands: Another look at the long-term Stoddard Fire Research Plots at Tall Timbers Research Station" . Forest Ecology and Management. 264: 197–209. doi:10.1016/j.foreco.2011.10.014.
9. Willson, M. F., et al. (1979). Nectar production and flower visitors of Asclepias verticillata. American Midland Naturalist 102(1) 23–35.
10. Asclepias verticillata. Native American Ethnobotany. University of Michigan, Dearborn.