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Ambrosia acanthicarpa Hook.  

No occurrences found

Family: Asteraceae
flatspine bur ragweed
[Franseria acanthicarpa (Hook.) Coville, moreGaertneria acanthicarpa (Hook.) Britt.]
Ambrosia acanthicarpa image
Max Licher
  • FNA
  • Gleason & Cronquist
  • Field Guide
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John L. Strother in Flora of North America (vol. 21)
Annuals, 10-80+ cm. Stems erect. Leaves opposite (proximal) and alternate; petioles 5-15(-25+) mm; blades ± deltate, 15-40(-85+) × 12-35(-80+) mm, 1-2-pinnately lobed, bases cuneate, ultimate margins entire or toothed, abaxial faces hispid and strigillose to sericeous, adaxial faces strigillose and gland-dotted. Pistillate heads clustered, proximal to staminates; florets 1. Staminate heads: peduncles 0.5-2 mm; involucres shallowly cup-shaped (usually each with 1-5+ black nerves), 3-5(-7) mm diam., sparsely hirsute or glabrous; florets 6-12(-20+). Burs: bodies fusiform to obpyramidal, 3-5 mm, ± hirsutulous or glabrate, spines 8-18+, scattered, stoutly subulate (sometimes basally flattened or navicular), 2-4(-5) mm, tips straight or uncinate. 2n = 36. Flowering (Apr-)Jul-Nov. Canyons, sandy flats, dunes; 10-3000 m; Alta., Man., Sask.; Ariz., Calif., Colo., Idaho, Kans., Minn., Mo., Mont., Nebr., Nev., N.Mex., N.Dak., Okla., Oreg., S.Dak., Tex., Utah, Wash., Wyo.
Vascular plants of NE US and adjacent Canada
Branching annual 1-8 dm, coarsely strigose to scabrous-hispid or both; lvs petioled, opposite below, alternate above, bipinnatifid (or the upper sessile and once pinnatifid), the blade 2-8 cm; heads numerous in terminal-racemiform clusters, sometimes chiefly staminate or chiefly pistillate; fruiting invols solitary or clustered in the upper axils, 5-10 mm, 1- fld and 1-beaked, with several series of flattened, divergent spines, these sometimes reduced in the chiefly staminate plants; 2n=36. Open places, especially in sandy soil; Wash. to Calif., e. to Sask. and Tex., and occasionally intr. eastward, as in Minn. and Mo. July-Oct. (Franseria a.; Gaertneria a.)

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

©The New York Botanical Garden. All rights reserved. Used by permission.
FNA 2006, Kearney and Peebles 1969, Heil et al 2013
Duration: Annual Nativity: Native Lifeform: Forb/Herb General: Annual herbs, 10-80 cm or more tall; stems erect; herbage bluish-gray or green, appearing dusty with the farinose or glandular pubescence that covers the plant. Leaves: Lower leaves opposite and upper leaves alternate, on petioles 5-15 mm long; blades ovate or deltoid in outline, pinnatifid 1-3 times, ultimate margins entire or toothed; entire leaf to 4 cm long or more, leathery and thick, with stiff hairs all over and stipitate-glands on the upper surface; sometimes lighter in color beneath. Flowers: Pistillate and staminate flowers in separate heads; all heads discoid; staminate heads pendant in terminal racemes, with a few pistillate heads at the base of each raceme. Pistillate heads with 1-5 florets, these lacking corollas; the entire head develops into a single spiny bur at maturity. Staminate heads with cup-shaped involucres, 2-6 mm in diameter, the phyllaries (bracts) connate in 1 series; containing 5-60 disc flowers, the corollas 5-lobed, whitish or purplish. Fruits: Burs 4-8 mm long, with 1 beak, armed with 6-30 strongly flattened, straight, spreading spines 2-5 mm long. Ecology: Found on dry to moist sandy soils, often in disturbed habitats, from 1,000-7,000 ft (305-2134 m); flowering June-December. Distribution: Western N. Amer., from MN to Alberta, south to w TX, NM, AZ, CA, and n MEX. Notes: This is a weedy annual Ambrosia. Look for the dissected leaves which are more or less hairy and sometimes tinged with blue or purple; the racemes of pendant male flowering heads which can look yellowish inside due to the color of the stamens, and late in the season, a few small spiny burs, 4-8 mm long, near the bottom of the racemes. Ambrosia confertiflora is similar, but that species is perennial, and has smaller burs (2-4 mm) with hooked spines (A. acanthicarpa has straight spines). Ambrosia psilostachya also appears similar, but that species is a perennial with running rootstock, and the fruits usually do not have spines on them. Ethnobotany: An infusion of the plant was taken for menstrual obstructions, and the ground root was placed in the tooth for toothache. The ash of the leaves was used in ceremonies. Etymology: Ambrosia is Greek for food of the gods, while acanthicarpa means having thorny fruits. Synonyms: Franseria acanthicarpa Editor: LCrumbacher 2011, AHazelton 2015
Ambrosia acanthicarpa
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Ambrosia acanthicarpa image
Max Licher
Ambrosia acanthicarpa image
Max Licher
Ambrosia acanthicarpa image
Max Licher
Ambrosia acanthicarpa image
Max Licher
Ambrosia acanthicarpa image
Max Licher
Ambrosia acanthicarpa image
Patrick Alexander
Ambrosia acanthicarpa image
Patrick Alexander
Ambrosia acanthicarpa image
Patrick Alexander
Ambrosia acanthicarpa image
Patrick Alexander
Ambrosia acanthicarpa image
Gregory Gust
Ambrosia acanthicarpa image
Gregory Gust
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