Skip to content

A Comprehensive Guide to Slim-leaf Milkweed (Asclepias stenophylla)

Slim-leaf Milkweed (Asclepias stenophylla) is a herbaceous perennial that is native to the south-central and mid-western United States. This plant is a host to the Queen (Danaus gilippus) and Monarch (Danaus plexippus) butterflies. Growing from 0.5 to 3 feet tall, this species has greenish-white flowers that bloom from June to August. It is hardy in zones 3-9.

Taxonomy and Naming of Slim-leaf Milkweed (Asclepias stenophylla)

Herbarium specimen of slim-leaf milkweed (Asclepias stenophylla).
Herbarium Specimen — Asclepias stenophylla A.Gray collected in United States of America by The New York Botanical Garden (licensed under CC BY 4.0)
Isotype specimen of slim-leaf milkweed (Asclepias stenophylla).
Isotype Specimen — Polyotus angustifolius Nutt. collected in United States of America by The New York Botanical Garden (licensed under CC BY 4.0)


Slim-leaf Milkweed (Asclepias stenophylla) was originally named and described by Thomas Nuttall, an American botanist, in 1837 as Polyotus angustifolius. Later in 1844, Joseph Decaisne, named the species Acerates angustifolia. In 1876, Asa Gray, gave the species its current name. The species has kept this name since this time and is a member of the Dogbane Family (Apocynaceae).

Meaning of the Scientific and Common Names

Scientific Name

The genus name, Asclepias, is named for the Greek god of healing, Asklepios (Flora of Wisconsin). The species name, stenophylla, comes from the Greek word, stenos, meaning narrow and leaf (phyllos) for leaf. It refers to the narrow leaves of the plant.

Common Name and Alternative Names

The common name comes from the slim or narrow leaves of the plant. Other common names include narrow-leaved green milkweed.

Physical Description of Slim-leaf Milkweed (Asclepias stenophylla)

Close-up of Yellowish flowers of slim-leaf milkweed (Asclepias stenophylla).
Flowers of Slim-leaf Milkweed (Asclepias stenophylla) — Samuel A. Schmid, CC BY 4.0, via Wikimedia Commons


  • Plant Type: This plant is a herbaceous perennial
  • Height: 0.8 to 3 feet
  • Stem: The stem is slender and sparsely pubescent to glabrous (Woodson 1954).
  • Leaves: The leaves are alternate to subopposite, simple, entire, and linear in shape. The leaves are 2 to 7 inches long and about 0.03 to 0.3 inches wide.
  • Flower color: greenish-white
  • Blooming period: This plant blooms from June to August.
  • Fruiting type and period: This plant has follicles that mature in the late summer and fall.

Range of Slim-leaf Milkweed (Asclepias stenophylla) in the United States and Canada

Range map of slim-leaf milkweed (Asclepias stenophylla) in the United States and Canada.
Range Map Credit: Kartesz, J.T., The Biota of North America Program (BONAP). 2023.(website Chapel Hill, N.C. [maps generated from Kartesz, J.T. 2023. Floristic Synthesis of North America, Version 1.0. Biota of North America Program (BONAP). (in press)]

This milkweed species is native to the south-central and mid-western United States. This species is considered to be rare in the states of Montana, Colorado, Minnesota, Iowa, Illinois, and Louisiana.


Prairie habitat in United States.
Prairie Habitat — USFWS Mountain-Prairie, Public domain, via Wikimedia Commons

This species grows in dry, gravel prairies, and sandy areas.

Hosted Insects

Monarch butterfly on green flower.
Green Flower with Monarch Butterfly — U.S. Fish and Wildlife Service, Public domain, via Wikimedia Commons

Other Supported Wildlife

Metallic bee on white flower.
Metallic Bee — David Whelan, CC0, via Wikimedia Commons

This species is a nectar source to other butterflies, skippers, bees, and wasps during the growing season.

Frequently Asked Questions about Slim-leaf Milkweed (Asclepias stenophylla)

Is this plant poisonous?

Like other milkweeds, it has cardiac glycosides (cardenolides) and is considered to be poisonous with ingestion.

Does this plant have any ethnobotanical uses?

The Native American Ethobotanical Database shows that this plant has been used as a dietary aid.

How is this plant distinguished from other milkweeds?

This species is similar to Rusby’s milkweed (Asclepias rusbyi) (Woodson 1954) and Engelmann’s milkweed (Asclepias engelmanniana) (Holzinger 1892), but the other two species have spreading or reflexed leaves, whereas the subject species has ascending leaves. At one point, Engelmann’s milkweed was considered to be the same species with Asclepias stenophylla (Holzinger 1892). Green comet milkweed (Ascleipias viridiflora) also looks like this species, but Asclepias viridiflora has leaves that are more opposite and larger flowers (Heidel and Dueholm 1995). Two other species to be careful of are whorled milkweed (Asclepias verticillata) and plains milkweed (Asclepias pumila). However these two species have more filiform leaves and the leaves are shorter (Vanderhorst 1998).

Is this plant invasive?

This plant has not been shown to be invasive in the literature.

Gardening with Slim-leaf Milkweed (Asclepias stenophylla)

Add Slim-leaf Milkweed to Your Garden

The link below takes you to our product page where we get a small commission from your purchase at no additional cost to you.

Plant of slim-leaf milkweed (Asclepias stenophylla).
Plant of Slim-leaf Milkweed — Asclepias stenophylla A.Gray observed in United States of America by Craig Martin (licensed under CC0 1.0)


This species is hardy in zones 3-9. If your garden is within these zones and you have the right growing conditions (soil, moisture and exposure), you may well be able to grow this plant. However, if planted outside of its range, the hosted species may not recognize the plant or be harmed by ingesting a different species with an unfamiliar chemical composition.

Optimal Conditions

This species grows best in places where it can receive full and has dry sandy and/or gravelly soils.


  • Heidel, Bonnie L. and Keith H. Dueholm. 1995. Sensitive Plant survey in the Sioux District, Custer National Forest, Carter County, Montana, and Harding County, South Dakota. (Helena, MT: Montana Natural Heritage Program).
  • Holzinger, J.M. 1892. The Identity of Asclepias stenophylla and Acerates auriculata. Botanical Gazette 17(5): 160.
  • Vanderhorst, James P., Stephen P. Cooper, and Bonnie L. Heidel. 1998. Botanical and Vegetation Survey of Carter County, Montana, Bureau of Land Management-administered Lands. (Helena, MT: Montana Natural Heritage Program).
  • Woodson, Robert E. 1954. The North American Species of Asclepias L. Annals of the Missouri Botanical Garden 41: 1-211.
Share this post on social!

Leave a Reply

Your email address will not be published. Required fields are marked *

five × three =


Robert Coxe

Robert Coxe is a professional ecologist and botanist who has worked as the State Ecologist of Delaware and as an ecologist for the Western Pennsylvania Conservancy. He is also a former Past-President of the Pennsylvania Academy of Science. He currently is an innkeeper at McMullen House Bed & Breakfast LLC and a web designer and owner for Silphium Design LLC.