Ambrosia artemisiifolia |
Ambrosia bidentata |
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annual ragweed, common ragweed, petite herbe à poux |
lance-leaf ragweed |
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Habit | Annuals, 10–60(–150+) cm. | Annuals, 10–30(–100+) cm. |
Stems | erect. |
erect. |
Leaves | opposite (proximal) and alternate; petioles 25–35(–60+) mm; blades deltate to lanceolate or elliptic, 25–55(–90+) × 20–30(–50+) mm, 1–2-pinnately lobed, bases cuneate, ultimate margins entire or toothed, abaxial faces sparsely pilosulous to strigillose, adaxial faces strigillose, both gland-dotted. |
mostly opposite; petioles 0–0.5 mm; blades ± lanceolate to lance-linear, 15–40+ × 3–6(–10+) mm, bases rounded to cordate, margins entire or with (1–)2(–4) basal lobes, abaxial and adaxial faces ± piloso-hispid and gland-dotted. |
Staminate heads | peduncles 0.5–1.5 mm; involucres shallowly cup-shaped (usually without black nerves), 2–3+ mm diam., glabrous or hispid to pilosulous; florets 12–20+. |
peduncles 0–0.5 mm; involucres obliquely cup-shaped (lateral lobe longer than others), 2.5–4 mm diam., piloso-hispid; florets 6–8+. |
Pistillate heads | clustered, proximal to staminates; florets 1. |
clustered, proximal to staminates; florets 1. |
Burs | bodies ± globose to pyriform, 2–3 mm, ± pilosulous, spines or tubercles 3–5+, near middles or distal, ± conic to acerose, 0.1–0.5+ mm, tips straight. |
bodies pyramidal, 5–8 mm, piloso-hispid, spines 4(–5), ± distal, ± acerose, 0.5–1 mm, tips straight. |
2n | = 34, 36. |
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Ambrosia artemisiifolia |
Ambrosia bidentata |
|
Phenology | Flowering Jul–Oct. | Flowering Jul–Oct. |
Habitat | Wet to dry soils, disturbed sites | Dry, disturbed sites |
Elevation | 0–1000+ m (0–3300+ ft) | 200–500 m (700–1600 ft) |
Distribution |
AK; AL; AR; AZ; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; NC; ND; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; SD; TN; TX; UT; VA; VT; WA; WI; WV; WY; AB; BC; MB; NB; NF; NS; NT; ON; PE; QC; SK
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AL; AR; CT; DC; GA; IA; IL; IN; KS; KY; LA; MD; MN; MO; MS; NC; OH; OK; TN; TX; VA; WV
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Discussion | Hybrids between Ambrosia artemisiifolia and A. psilostachya have been called A. ×intergradiens W. H. Wagner. The name Ambrosia ×helenae Rouleau applies to hybrids between A. artemisiifolia and A. trifida. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Hybrids between Ambrosia bidentata and A. trifida have been recorded. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 21, p. 15. | FNA vol. 21, p. 15. |
Parent taxa | Asteraceae > tribe Heliantheae > subtribe Ambrosiinae > Ambrosia | Asteraceae > tribe Heliantheae > subtribe Ambrosiinae > Ambrosia |
Sibling taxa | ||
Synonyms | A. artemisiifolia var. elatior, A. artemisiifolia var. paniculata, A. elatior, A. glandulosa, A. monophylla | |
Name authority | Linnaeus: Sp. Pl. 2: 988. (1753) | Michaux: Fl. Bor.-Amer. 2: 182. (1803) |
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