Eupatorium maculatum L.

• Authority

  Lamont, E. E. 1995. Taxonomy of section (Asteraceae). Mem. New York Bot. Gard. 72: 1-68.

• Family

  Asteraceae

• Scientific Name

  Eupatorium maculatum L.

• Description

  Species Description - Erect herb, 0.6-2 m tall; sterns solid or sometimes hollow near the base at maturity, purple-spotted or sometimes uniformly purple throughout, glandular-puberulent near summit, glabrous below to densely puberulent throughout, scarcely or not at all glaucous. Leaves mostly in (3’s) 4’s or 5’s (6’s); blades lance-elliptic to lanceolate or lance-ovate, mostly (6-)8-23(-30) cm long, (1.5-)2-7(-9) cm wide, gradually or sometimes abruptly tapering to the short-petiolate base, acuminate at the apex, pinnately veined, sharply serrate or doubly serrate, adaxial surface glabrous to sparingly glabrescent, abaxial surface atomiferous and glabrate to densely pubescent; petioles usually 0.5-2 cm long, glabrous to pubescent. Inflorescence flat-topped, usually less than 20 cm wide in life, heads short pedunculate. Involucre 6.5-9 mm high, 3.5-7 mm wide, often purplish; bracts 10-22, glabrous to densely pubescent, lanceolate, obtuse at apex, strongly imbricate, few-striate or at least with prominent midvein; receptacle naked, flat or weakly convex. Flowers (8-)9-20(-22) in a head; corolla 4.5-7.5 mm long, 5-toothed, purplish, funnel-form, outer surface usually minutely atomiferous-glandular, lobes ovate to deltate, usually slightly longer than wide; style base puberulous, enlarged. Achene prismatic, 3.0-4.5 mm long, 5-ribbed, atomiferous-glandular, sometimes with a few setulae along the nerves; pappus a single series of 25-40 slender, capillary, scabrous, persistent bristles. 2n = 20.

• Discussion

  Type. Without locality and date, K[alm] s.n. (there is only one specimen of E. maculatum in the herbarium of Linnaeus according to Savage, 1945, page 143) [holotype, LINN (microfiche, NY!; photo, GH!)]. Eupatorium verticillatum Lam. var. ß, Encycl. 2: 405. 1786 (non Eupatorium verticillatum Muhl. ex Willd., Sp. pl. 3: 1760. 1804). Type. No specimens were directly cited in the protologue, which evidently applies to what we would now call E. maculatum L. It seems clear that Lamarck intended to include E. maculatum L. in his E. verticillatum var. ß, although the citation is indirect. Lamarck’s name is therefore nomenclaturally superfluous under Article 63.1 of the Code (Greuter, 1988), and ought to be typified on E. maculatum L. (see Article 7.13 of the Code). (See additional discussion under E. verticillatum var. a, listed in synonymy under E. purpureum L.). Eupatorium maculatum var. ß urticifolium Barratt, Eupatoria verticillata no. 2. 1841. Type. United States. Connecticut. In the Middletown meadows, near the banks of the Connecticut [River], s.d., Barratt s.n. (holotype, NY!). Eupatorium maculatum f. faxoni Fernald, Rhodora 47: 195. 1945. Eupatorium purpureum f. faxoni (Femald) Boivin, Phytologia 23: 11. 1972. Type. United States. New Hampshire. [Carroll Co.]: Gate of Crawford Notch, 2 Sep 1884, Faxon s.n. (holotype, GH!; isotype, GH!). Eupatorium maculatum L. (Figs. 25 & 26) has the widest geographic distribution and greatest morphological variability of all species in sect. Verticillata. Three infraspecific taxa have been proposed for Eupatorium maculatum, but recognition of these taxa has varied among botanists. For example, the western variety bruneri (A. Gray) Breitung was recognized by Cronquist (1952b, 1955a), Gleason and Cronquist (1963, 1991), King and Robinson (1980), Barkley (1986), Looman and Best (1987), and Welsh et al. (1987); however, no taxonomic recognition of this taxon was given by Wiegand and Weatherby (1937), Fernald (1950), Rousseau (1974), or Scoggan (1979). Conversely, the variety foliosum (Fern.) Wiegand was recognized by Wiegand and Weatherby (1937), Scoggan (1950), Fernald (1950), Erskine (1960), Roland and Smith (1969), Gardner (1973), and Seymour (1982); however, this taxon was not recognized by Gleason and Cronquist (1963), Scoggan (1979), King and Robinson (1980), Hinds (1986), or Mitchell (1986). Herbarium studies indicate that distinct phenetic differentiation exists within Eupatorium maculatum, and these recognizable differences are correlated with geography (Figs. 9-11). Field observations confirm this; however, geographic and morphological lines of demarcation separating these infraspecific taxa are not precise. A revised taxonomic interpretation of the group better reflects the totality of similarities and differences among infraspecific taxa. The wide-ranging western taxon, subsp. bruneri (A. Gray) G. W. Douglas, could almost stand as a distinct taxonomic species, as proposed by Gray (1884), until the eastern limit of its range is studied and a “sloppy,” imprecise transition into Eupatorium maculatum s.str. is observed. Conversely, the northeastern taxon of the Canadian maritimes, var. foliosum, does not warrant equal taxonomic recognition with its western counterpart, due to its more restricted range, limited phenetic differentiation, and even more “sloppy,” imprecise transition into E. maculatum s.str. The southern range of var. foliosum has been described as extending into southern Maine (Bean et al., 1966), central New Hampshire (Seymour, 1982), central Vermont (Dole, 1937), and central New York (Smith, 1968). However, field studies indicate the southernmost part of this distribution pattern is the result of misrepresentation in herbaria. Within some populations of E. maculatum s.str. are individuals that approach var. foliosum; however, these populations as a whole do not reflect affinity with var. foliosum. Based on herbarium specimens and field observation, I find the southern limit of var. foliosum to be in northernmost New York, northern New Hampshire, northern Vermont, and northern Maine. In the area where their distributions overlap (Figs. 9, 10), var. foliosum usually occurs at higher elevations than does var. maculatum. To recapitulate, Eupatorium maculatum is a morphologically complex species with attributes that warrant a hierarchal infraspecific organization of taxa. A comparison between the two subspecies of E. maculatum is summarized in Table IX.