Montana Field Guide

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Montana Field Guides

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- Kingdom - Plants - Plantae
  - Division - Flowering Plants - Anthophyta
    - Class - Dicots - Dicotyledoneae
      - Order - Aster/Sunflowers - Asterales
        
        Family - Aster/Sunflowers - Asteraceae
        
        Species - Flat-spine Ragweed - Ambrosia acanthicarpa

Flat-spine Ragweed - Ambrosia acanthicarpa

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Native Species

Global Rank: G5
State Rank: S3S4
C-value:

Agency Status
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General Description

Taprooted annual. Stems erect, simple or branched, 10–50 cm. Herbage hispid, strigose. Leaves mostly alternate; blade broadly ovate, 2–8 cm long, twice pinnatifid into ovate ultimate segments. Female heads 1-flowered. Male heads cup-shaped, black-veined, 3–5 mm wide with 6 to 12 florets, spreading on peduncles 1–2 mm long. Bur 3–5 mm long, oblong, villous with stout spines (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Range Comments

WA and AB to MN south to CA, AZ and TX (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Observations in Montana Natural Heritage Program Database

Number of Observations: 4

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Relative Density

Recency

(Observations spanning multiple months or years are excluded from time charts)

Habitat

River banks; plains, valleys (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

References

Literature Cited AboveLegend: View Online Publication
- Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?
- Heidel, B.L. 1994. Sensitive plant species survey in Garfield and McCone Counties, Montana. Unpublished report to the Bureau of Land Management. Montana Natural Heritage Program, Helena, Montana. 58 pp. plus appendices.
- Lesica, P., M.T. Lavin, and P.F. Stickney. 2022. Manual of Montana Vascular Plants, Second Edition. Fort Worth, TX: BRIT Press. viii + 779 p.
- Quire, R.L. 2013. The sagebrush steppe of Montana and southeastern Idaho shows evidence of high native plant diversity, stability, and resistance to the detrimental effects of nonnative plant species. M.Sc. Thesis. Bozeman, MT: Montana State University. 124 p.
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Citation for data on this website:
Flat-spine Ragweed — Ambrosia acanthicarpa. Montana Field Guide. Montana Natural Heritage Program. Retrieved on October 4, 2024, from https://FieldGuide.mt.gov/speciesDetail.aspx?elcode=PDAST0C010