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Sullivant’s Milkweed (Asclepias sullivantii), an Easy Guide in 10 Sections

Introduction

Sullivant’s Milkweed (Asclepias sullivantii) is a herbaceous perennial that is found in the midwestern United States and Ontario in Canada. This milkweed is a host plant to the Monarch Butterfly and a nectar plant to others. It can grow from 2 to 5 feet tall and has ovate shaped leaves. The pink to purple flowers bloom from June to July. It is hardy in zones 3-7 and prefers open areas with full sun that have moist to mesic soil. The seeds for this plant can be purchased in the McMullen House Bed & Breakfast Garden Shop.

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Taxonomy and Naming of Sullivant’s Milkweed (Asclepias sullivantii)

Herbarium specimen of Sullivant's Milkweed (Asclepias sullivantii).
Sullivant’s Milkweed — Asclepias sullivantii Engelm. ex A.Gray collected in United States of America by The New York Botanical Garden (licensed under CC BY 4.0)

Taxonomy

Sullivant’s Milkweed (Asclepias sullivantii) was named by George Engelmann, a German American botanist. This plant is a member of the Dogbane Family (Apocynaceae).

Meaning of the Scientific Names and Common Names

Scientific Name

The genus name, Asclepias, is named for the Greek god of healing, Asklepios (Flora of Wisconsin). The species name, sullivantii, is in honor of William Starling Sullivant, an American botanist (Missouri Botanical Garden).

Common and Alternative Names

The common name of this species is in reference to the species name. Other common names, such as prairie milkweed, describe the habitat of the plant. Another name, smooth milkweed, is in reference to the texture of the stem and silk weed, describes the downy texture of the seeds.

Physical Description of Sullivant’s Milkweed (Asclepias sullivantii)

Plant of Sullivant's Milkweed (Asclepias sullivantii) in a field.
Sullivant’s Milkweed in a field — Asclepias sullivantii Engelm. ex A.Gray
observed in United States of America
by samk (licensed under CCO 1.0)

Description

  • Plant Type: Herbaceous perennial
  • Height: 2 to 5 feet tall
  • Leaves: opposite, simple, entire, fleshy, oblong to oblong-ovate leaves up to 3-6 inches in length and 1.5-3 inches in width. The leaves are short-petiolate or sometimes sessile.
  • Stem: the stem is described as being smooth (Minnesota DNR)
  • Flower color: pink to purplish
  • Blooming period: June to July
  • Fruiting type and period: follicle that comes out in the late summer

Range of Sullivant’s Milkweed in the United States and Canada

Range Map of Sullivant's Milkweed (Asclepias sullivantii) in the United States and Canada.

This species is native to the mid-western United States and the province of Ontario in Canada. It is considered to be rare in South Dakota, Minnesota, Wisconsin, Michigan, and Ontario in Canada.

Habitat

Prairie habitat in Ohio.
Prairie habitat — Sixflashphoto, CC BY-SA 4.0, via Wikimedia Commons

As one of the common names suggests, this plant grows in open areas such as prairies, but it can also be found in meadows, railroad edges, and roadsides. It was originally associated with tallgrass prairies, but a lot of these prairies have been replaced by cornfields (Minnesota DNR). In the mid-1800s it was reported to be on wet meadows of the Missouri River (Smithsonian 1850).

Hosted Insects

Monarch butterfly (Danaus plexippus) on a green flower.
Monarch Butterfly on a green flower — U.S. Fish and Wildlife Service, Public domain, via Wikimedia

This milkweed, like a lot of milkweeds, is a host to the Monarch Butterfly (Danaus plexippus). It is also a host to the Queen Butterfly (Danaus gilippus).

Other Supported Wildlife

Bumblebee on a pink flower.
Bumblebee on a pink flower — Weerlicht, CC0, via Wikimedia Commons

This milkweed, like a lot of other milkweeds, is a nectar source to other insect species, including bees, wasps, flies, and butterflies. Ruby-throated hummingbirds are known to use this species as a nectar source. Like the common milkweed, this species is used by various milkweed beetles adapted to the toxins.

Frequently Asked Questions about Sullivant’s Milkweed (Asclepias sullivantii)

What species are similar to this one?

Common milkweed (Asclepias syriaca) looks like this species, but common milkweed has more flowers and downy hairs. In vegetative specimens, Sullivant’s milkweed is confused with American hemp (Apocynum cannabinum) (Minnesota DNR).

Is this plant poisonous?

This plant, like all members of the milkweed (Asclepias), contains cardiac cardenolides. The cardenolides are in the milky sap and make this plant poisonous if ingested, however, for the monarch butterflies it make them unpalatable.

Gardening with Sullivant’s Milkweed (Asclepias sullivantii)

Plant of Sullivant's Milkweed (Asclepias sullivantii) in a field.
Asclepias sullivantii Engelm. ex A.Gray
observed in United States of America
by Nancy Navarre (licensed under CCO 1.0)

Hardiness

This species is hardy in zones 3-7. If your garden is within these zones and you have the right growing conditions (soil and moisture), you may well be able to grow this plant. Since the hosted species, the monarch and queen butterflies, are wide ranging they will likely be in your area.

Optimal Conditions

This species prefers open areas with full sun that have mesic to dry sandy soil.

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References

  • Smithsonian Institute. 1850. Annual report of the Board of Regents of the Smithsonian Institution. United States National Museum. Washington, DC.
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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 for Silphium Design LLC.

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