Parthenium hysterophorus |
Parthenium integrifolium |
|
---|---|---|
ragweed parthenium, Santa Maria, Santa Maria feverfew, whitetop weed |
American feverfew, wild feverfew, wild quinine |
|
Habit | Annuals, (10–)30–120+ cm. | Perennials, 30–60(–100+) cm. |
Leaf | blades ovate to elliptic, 30–180+ × 10–50(–90+) mm, (1–)2-pinnately lobed (ultimate lobes lanceolate to linear, 3–50 × 2–15 mm), faces sparsely to densely scabrellous and gland-dotted (seldom with additional erect hairs 1–2 mm). |
blades ovate to lanceolate, 30–350+ × 20–120+ mm, margins usually crenate to serrate, sometimes coarsely toothed or somewhat lobed (then mostly toward bases), faces hispid to hirtellous or ± scabrous, gland-dotted. |
Peduncles | 1–8(–15+) mm. |
1–8(–12+) mm. |
Pistillate florets | 5(–6); corolla laminae reniform or orbiculate to oblong, 0.3–1 mm. |
5(–6); corolla laminae ovate to oblong or orbiculate, 1–2+ mm. |
Disc florets | 12–30[–60]. |
15–35+. |
Phyllaries | outer 5(–6), lance-elliptic, 2–4 mm, inner 5(–6) ovate to ± orbiculate, 2.5–4 mm. |
outer 5(–6) lanceolate to broadly ovate, 3–5 mm, inner 5(–6) ± orbiculate, 4–6 mm. |
Heads | obscurely radiate, borne in open, paniculiform arrays. |
radiate, borne in corymbiform to paniculiform arrays. |
Cypselae | obovoid, 1.5–2(–3.5) mm; pappus-like enations erect, deltate to ovate, 0.5–1 mm (sometimes a third, subulate spur near apex adaxially). |
± obovoid, 3–4+ mm; pappus-like enations 0 or 2(–4), erect to spreading, ± subulate or threadlike, fragile, 0.3–0.6+ mm. |
2n | = 34. |
= 72. |
Parthenium hysterophorus |
Parthenium integrifolium |
|
Phenology | Flowering Mar–Nov. | Flowering May–Sep. |
Habitat | Disturbed sites | Glades and barrens, prairies, disturbed sites |
Elevation | 0–300 m (0–1000 ft) | 10–500 m (0–1600 ft) |
Distribution |
AL; AR; CT; DC; DE; FL; IL; KS; LA; MA; MD; MI; MO; MS; NJ; NM; NY; OH; OK; PA; TX; VA; Mexico [Introduced in subtropical, tropical, and warm-temperate New World and Old World]
|
AL; AR; CT; GA; IA; IL; IN; KS; KY; LA; MA; MI; MN; MO; MS; NC; NY; OH; OK; PA; SC; TN; TX; VA; WI; WV
|
Discussion | In some places, especially in Old World, Parthenium hysterophorus causes serious contact dermatitis in humans. The plants should be handled with caution. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
As evidenced by the synonymy, Parthenium integrifolium as here circumscribed has been variously partitioned by other taxonomists. For the present, I see no justification for segregating species from, or for formal recognition of infraspecific taxa within P. integrifolium. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 21, p. 22. | FNA vol. 21, p. 22. |
Parent taxa | Asteraceae > tribe Heliantheae > subtribe Ambrosiinae > Parthenium | Asteraceae > tribe Heliantheae > subtribe Ambrosiinae > Parthenium |
Sibling taxa | ||
Synonyms | P. auriculatum, P. hispidum, P. hispidum var. auriculatum, P. integrifolium var. auriculatum, P. integrifolium var. henryanum, P. integrifolium var. hispidum, P. integrifolium var. mabryanum, P. radfordii | |
Name authority | Linnaeus: Sp. Pl. 2: 988. (1753) | Linnaeus: Sp. Pl. 2: 988. (1753) |
Web links |
|