Swamp Milkweed - Asclepias incarnata
State Rank Reason (see State Rank above)
Known in Montana from Carbon County. One of the known sites is likely extirpated. Additional information is needed on the species' distribution, abundance, potential trends and threats within Montana.
- Details on Status Ranking and Review
Swamp Milkweed (Asclepias incarnata) Conservation Status Review
Review Date =
Fibrous-rooted. Stems simple to branched, 70–100 cm. Herbage glabrous to puberulent on the stem. Leaves opposite, spreading; blades lanceolate, 4–15 cm long. Umbels of 10 to 40 flowers; peduncles 1–7 cm long. Flowers 9–11 mm high; sepals villous, 1–2 mm long; petals purplish, glabrous, 5–6 mm long; gynostegium pink, glabrous, 1–2 mm high; hoods oblong, 2–3 mm long; horns exserted, arching. Follicles erect, fusiform, 5–8 cm long, smooth, mostly glabrous (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX)
Our plants are variety incarnata
Flowering in July.
The combination of acute leaves >4 mm wide and slender horns longer than the hoods distinguish Asclepias incarnata from other Montana milkweeds. Asclepias speciosa also has pinkish corollas and occupies wetland habitat, but has large hoods that surpass the horns.
SK to NS south to NM and FL. Known from Carbon and Wibaux counties (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).
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)
Wet meadows and thickets.
Ecological Systems Associated with this Species
- Additional ReferencesLegend: View Online Publication
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- Heidel, B. 1994. Potential impact of proposed noxious weed treatment at Bluewater Fish Hatchery (MDFWP) on plant species of special concern. Unpublished report to Gary Shaver, Bluewater Fish Hatchery. Montana Natural Heritage Program, Helena, Montana. 5 pp.
- Heidel, B. 1994. Sensitive species survey of Bluewater Fish Hatchery of 10 June; memo and documentation provided to Gary Shaver, MDFWP.
- Lesica, P., M. T. Lavin, and P. F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.