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Montana Field Guide

Montana Field Guides

Giant Ragweed - Ambrosia trifida


Global Rank: G5
State Rank: SNA

Agency Status
USFWS:
USFS:
BLM:
MNPS Threat Rank:
C-value: 2

External Links






 
General Description
Taprooted annual. Stems erect, simple or branched, 30–150 cm, strigose to hispid. Leaves opposite; blade lanceolate to broadly ovate, 4–15 cm long, serrate, often 3-lobed, hispid, glandular. Female heads 1-flowered. Male heads saucer-shaped, black-veined, 2–4 mm wide, villous, hispid, glandular with 3 to 25 florets, nodding on peduncles 1–3 mm long. Bur 3–5 mm long, deltoid, ribbed, glabrous with ca. 5 erect spines (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Species Range
Present
 


Range Comments
Roadsides, fields, streambanks; plains, valleys (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Summary of Observations Submitted for Montana
Number of Observations: 6

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density

Recency

 

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



Habitat

References
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Citation for data on this website:
Giant Ragweed — Ambrosia trifida.  Montana Field Guide.  .  Retrieved on , from