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Published In: Species Plantarum 2: 837. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library

Project Name Data (Last Modified On 8/11/2017)
Acceptance : Accepted
Project Data     (Last Modified On 7/9/2009)
Status: Native


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1. Eupatorium altissimum L. (tall thoroughwort)

Pl. 266 a–d; Map 1109

Stems 50–200 cm long, not hollow, moderately to densely short-hairy above the nearly glabrous basal portion, green to yellowish green, sometimes purplish-tinged or brownish-mottled, often somewhat glaucous, some nodes often with small fascicles of axillary leaves less than 1/2 as long as the main stem leaves. Leaves mostly opposite, those of the uppermost nodes sometimes alternate, sessile or with poorly differentiated petioles to 15 mm long. Leaf blades 2–15 cm long, 3–25 mm wide, narrowly lanceolate to lanceolate or less commonly narrowly elliptic, tapered at the base, tapered to a sharply pointed tip, the margins entire or more commonly sharply toothed above the midpoint, the surfaces moderately to densely short-hairy, also densely gland-dotted, with 3 main veins from the base. Inflorescences terminal panicles, flat-topped or broadly dome-shaped. Involucre 4.5–7.0 mm long, more or less cup-shaped, the bracts ovate to narrowly oblong, rounded to bluntly pointed at the tip, the margins thin and pale, mostly faintly 3-nerved, densely short-hairy, green. Disc florets 5. Corollas 4–5 mm long, the surface often somewhat glandular, white. Fruits 1.5–2.5 mm long. 2n=20, 30, 40. August–October.

Scattered nearly throughout the state (eastern U.S. west to Minnesota, Nebraska, and Texas; Canada). Upland prairies, loess hill prairies, glades, savannas, openings of mesic to dry upland forests, banks of streams and rivers, and ledges and tops of bluffs; also old fields, fallow fields, pastures, ditches, quarries, railroads, roadsides, and open, disturbed areas.

For a discussion of presumed hybrids with E. hyssopifolium, see the treatment of that species.



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