Flora of North America species comparison

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Ambrosia cordifolia

Ambrosia cheiranthifolia

heartleaf bursage, Tucson bur ragweed, Tucson burr ragweed

Rio Grande ragweed
Habit Shrubs, 30–50+ cm. Perennials or subshrubs, 10–30+ cm (rhizomatous and/or soboliferous, colonial).
Stems

erect.

erect.
Leaves

mostly alternate;

petioles 3–35 mm;

blades deltate to rounded-deltate, 10–35(–80) × 10–30(–70) mm, bases cordate to truncate, margins coarsely toothed, abaxial faces densely puberulent (including veins), adaxial faces strigillose to scabrellous and gland-dotted.

opposite (distal sometimes alternate);

petioles 0;

blades lanceolate or lance-elliptic to lance-oblong or oblanceolate, 20–50(–70+) × 8–12(–25+) mm, rarely ± pinnately lobed (lobes ± deltate), bases cuneate (then rounded), margins entire or toothed, abaxial faces densely strigose (silvery gray), adaxial faces strigillose.
Staminate heads

peduncles 0–1 mm;

involucres cup-shaped, 2–3(–5) mm diam., strigillose;

florets 8–30+.

peduncles 1–4+ mm;

involucres cup-shaped (sometimes with black nerve in each lobe), 3–4+ mm diam., strigillose;

florets 8–18+.
Pistillate heads

clustered, proximal to staminates;

florets (1–)2.

clustered (in axils), proximal to staminates;

florets 1(–2).
Burs

bodies ± globose to fusiform, 3–4+ mm, tomentulose and stipitate-glandular, spines 8–20+, scattered, ± subulate (basally navicular), 1–2 mm, tips straight or uncinate.

bodies ± pyriform to ± globose, 2–3+ mm, glabrous or strigose, spines (1–)3–5+, scattered, stoutly conic, 0.4–0.8+ mm, tips straight (often each with black nerve).
2n

= 72.

Ambrosia cordifolia

Ambrosia cheiranthifolia
Phenology Flowering Mar–Apr. Flowering Jun–Nov.
Habitat Sandy washes, benches Seasonally wet clays or sands, scrublands
Elevation 700–1200 m (2300–3900 ft) 10–30+ m (0–100+ ft)
Distribution
from FNA
AZ; Mexico (Sinaloa, Sonora)
[WildflowerSearch map]
[BONAP county map]
from FNA
TX; Mexico (Tamaulipas)
[BONAP county map]
Source FNA vol. 21, p. 14. FNA vol. 21, p. 17.
Parent taxa Asteraceae > tribe Heliantheae > subtribe Ambrosiinae > Ambrosia Asteraceae > tribe Heliantheae > subtribe Ambrosiinae > Ambrosia
Sibling taxa
A. acanthicarpa, A. ambrosioides, A. artemisiifolia, A. bidentata, A. chamissonis, A. cheiranthifolia, A. chenopodiifolia, A. confertiflora, A. deltoidea, A. dumosa, A. eriocentra, A. grayi, A. hispida, A. ilicifolia, A. linearis, A. monogyra, A. psilostachya, A. pumila, A. salsola, A. tomentosa, A. trifida
A. acanthicarpa, A. ambrosioides, A. artemisiifolia, A. bidentata, A. chamissonis, A. chenopodiifolia, A. confertiflora, A. cordifolia, A. deltoidea, A. dumosa, A. eriocentra, A. grayi, A. hispida, A. ilicifolia, A. linearis, A. monogyra, A. psilostachya, A. pumila, A. salsola, A. tomentosa, A. trifida
Synonyms Franseria cordifolia
Name authority (A. Gray) W. W. Payne: J. Arnold Arbor. 45: 421. (1964) A. Gray: in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 87. (1859)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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