Eastern Mojave Vegetation Bur of Coll. No. 3540, Ambrosia trifida.  
 

 

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If you have a question or a comment about this photograph you may write to me at: tomas@schweich.com I sometimes post interesting questions in my FAQ, but I never disclose your full name or address. 		  Asteraceae, Ambrosia trifida
Microphotograph 14 October 2025.

Native and Naturalized Flora of the Golden Area, Jefferson County, Colorado
Asteraceae

Ambrosia trifida L.  Giant Ragweed.

Golden, Jefferson County, Colorado. North edge of privately-owned vacant land at approximately 1300 Avery Street. 39.77806°N, 105.23349°W. WGS 1984 Immediately adjacent to asphalt driveway with Ambrosia psilostachya. Coordinates estimated with GoogleEarth. Encountered as part of a native plant rescue activity with Golden's Weedbusters.

Collected by permit: LOT 27 LLC c/o Ball Properties, 2025, issued: Jul 1, 2025, to: Golden Weedbusters.

Tom Schweich 3540. 7-Oct-2025

Coll. No, 3540, 7 Oct 2025, characters observed: Annual, 60 cm.; Stem, erect; Leaves, opposite, petioles 4-8 mm., unlobed or palmately 3-lobed, unlobed, ellipto-lanceolate, 75 mm. × 21 mm. wide, margin crenate-serrate, adaxial green papillose-hispid, abaxial green papillose hispid; Pistillate heads, clustered in axils; Staminate heads, peduncles 1-1.3 mm., involucres cup-shaped, with black nerves; Burs, obpyramidal, body 5 mm. × 3 mm. wide + beak 3 mm. = 8 mm., spines, 5 in one series, distal.

Other photos about Species - Asteraceae or Ambrosia trifida.

 

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Date and time this page was prepared: 8/1/2026 3:18:48 PM