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heartleaf bursage, Tucson bur ragweed, Tucson burr ragweed

beach bur, beach bur-sage, cutleaf beach bur, silver beachweed, silver bur-ragweed, silver burr ragweed, silver burweed

Habit Shrubs, 30–50+ cm. Perennials, 50–150(–350+) cm.
Stems

erect.

prostrate or decumbent.

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.

mostly alternate;

petioles 15–30(–45+) mm;

blades rounded-deltate to ovate or obovate, 20–45(–70+) × 10–25(–50+) mm overall, not lobed or 1–2(–3)-pinnately lobed, bases cuneate, ultimate margins entire or toothed, abaxial and adaxial faces strigillose to sericeous.

Staminate heads

peduncles 0–1 mm;

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

florets 8–30+.

peduncles 0.5–2 mm;

involucres shallowly cup-shaped, 4–6+ mm diam., strigillose;

florets 8–25(–50).

Pistillate heads

clustered, proximal to staminates;

florets (1–)2.

clustered, proximal to staminates;

florets 1.

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 fusiform to ± pyriform, 4–7+ mm, ± strigillose to pilosulous, spines 8–16+, scattered, stoutly conic or flattened- to triquetrous-subulate, 0.5–1.5+ mm, tips straight.

2n

= 36.

Ambrosia cordifolia

Ambrosia chamissonis

Phenology Flowering Mar–Apr. Flowering Apr–Nov.
Habitat Sandy washes, benches Sandy beaches and strand
Elevation 700–1200 m (2300–3900 ft) 0–10 m (0–0 ft)
Distribution
from FNA
AZ; Mexico (Sinaloa, Sonora)
[WildflowerSearch map]
[BONAP county map]
from FNA
AK; CA; OR; WA; BC; Mexico (Baja California)
[WildflowerSearch map]
[BONAP county map]
Source FNA vol. 21, p. 14. FNA vol. 21, p. 16.
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. cheiranthifolia, 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 Franseria chamissonis, Franseria chamissonis subsp. bipinnatisecta, A. chamissonis var. bipinnatisecta
Name authority (A. Gray) W. W. Payne: J. Arnold Arbor. 45: 421. (1964) (Lessing) Greene: Man. Bot. San Francisco, 188. (1894)
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