Ovalleaf Milkweed - Asclepias ovalifolia
State Rank Reason (see State Rank above)
Known in the state from two sites in extreme eastern Montana. Additional information on population levels, threats and trends are needed.
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Ovalleaf Milkweed (Asclepias ovalifolia) Conservation Status Review
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Ovalleaf Milkweed is a rhizomatous perennial with usually solitary slender stems 2-6 dm high. The erect to spreading, opposite leaves have petioles which are up to 1 cm long, and broadly lance-shaped to elliptic blades which are 4-8 cm long with entire margins. Leaves are moderately long, hairy beneath, and the sap is milky. 1-3 umbrella-shaped, stalked clusters of 8-20 flowers are at the top of the stem or in the axils of the upper leaves. Each greenish-white to cream flower is 8-10 mm high and borne on a hairy stalk that is up to 20 mm long. Flowers have 5 reflexed corolla lobes which are 5-6 mm long, and 5 erect hoods which are 4-5 mm long and rounded at the tip; these hoods surround a greenish or yellowish central column, and each has a conical horn inside. The erect spindle-shaped fruits are 6-8 cm long and ca. 1 cm wide. Each fruit has numerous seeds, each with a light brown tuft of hairs that is 18-35 mm long.
Flowering in late June-early July.
Asclepias viridiflora and A. speciosa also have broad leaves, but the former lacks horns within the hoods, and the latter has pink to purple flowers.
Southern Alberta, Saskatchewan, and Manitoba south to Wyoming, Nebraska, northern Iowa and Illinois to the upper peninsula of Michigan.
Observations in Montana Natural Heritage Program Database
Number of Observations:
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(Observations spanning multiple months or years are excluded from time charts)
Open pine woodlands, prairies and dry riparian terraces.
Ecological Systems Associated with this Species
- Additional ReferencesLegend: View Online Publication
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- Heidel, B. L. 1996. Noteworthy collections - Montana. Madrono 43(3):436-440.
- Heidel, B.L. and K.H. Dueholm. 1995. Sensitive plant survey in the Sioux District, Custer National Forest, 1994, Carter County, Montana and Harding County, South Dakota. Unpublished report to the Custer National Forest. Montana Natural Heritage Program, Helena, Montana. 95 pp. plus appendices.
- Heidel, B.L., S.V. Cooper and C. Jean. 2000. Plant species of special concern and plant associations of Sheridan County, Montana. Report to U.S. Fish and Wildlife Service. Montana Natural Heritage Program, Helena, Montana. 96 p.
- Lesica, P., M. T. Lavin, and P. F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
- Vanderhorst, J.P., S.V. Cooper, and B.L. Heidel. 1998. Botanical and vegetation survey of Carter County, Montana. Unpublished report prepared for the Bureau of Land Management. Montana Natural Heritage Program, Helena. 116 pp. + app.