Eupatorium purpureum L.

• Authority

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

• Family

  Asteraceae

• Scientific Name

  Eupatorium purpureum L.

• Description

  Species Description - Erect herb, 0.3-2 m tall. Stems solid or rarely developing a slender central cavity toward the base, usually dark purple only at nodes, otherwise greenish or rarely purplish-green, glandular-puberulent near summit, glabrous below inflorescence, scarcely or not at all glaucous. Leaves mostly in 3’s or 4’s (rarely 5’s); blades lance-ovate or ovate to deltate-ovate, mostly (7-)9-26(-30) cm long, (2.5-)3-15(-18) cm wide, relatively abruptly or sometimes gradually tapering to the short-petiolate base, acuminate at the apex, pinnately veined, coarsely serrate with a large gland at apex of each marginal tooth, adaxial surface glabrous to sparingly glabrescent, abaxial surface atomiferous and glabrate to densely pubescent; petioles usually 0.5-1.5(-2) cm long, glabrous to sparingly puberulent or rarely ciliate. Inflorescence a loosely convex compound cyme, rather sparse, usually less than 20 cm wide in life, the branches ascending from widely diverging bases, heads short pedunculate, peduncles conspicuously glandular pubescent. Involucre 6.5-9 mm high, 2.5-5 mm wide, often purplish; bracts 10-22, lanceolate, obtuse at apex, well imbricate, few-striate or at least with prominent midvein; receptacle naked, flat or weakly convex. Flowers (4-)5-7(-8) in a head; corolla 4.5-7.5 mm long, 5-toothed, generally very pale pinkish or purplish, funnelform, 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. Protologue: “North America.” Without specific locality, date, and collector’s name (there is only one specimen of E. purpureum in the herbarium of Linnaeus according to Savage, 1945, page 143) [holotype, LINN (microfiche, NY!; photo, GH!)]. Eupatorium trifoliatum L., Sp. pl. 837. 1753. Eupatorium purpureum var. maculatum f. trifoliatum (L.) Voss, Vilm. Blumengartn., Ed. 3, 1: 447. 1894. Type. Protologue: “Virginia.” Without specific locality, date, and collector’s name (there is only one specimen of E. trifoliatum in the herbarium of Linnaeus according to Savage, 1945, page 143) [holotype, LINN (microfiche, NY!; photo, GH!)]. Eupatorium verticillatum Lam. var. a, Encycl. 2: 405. 1786 (non Eupatorium verticillatum Muhl. ex Willd. Sp. pl. 3: 1760. 1804). Eupatorium purpureum var. verticillatum (Lam.) Wood, Class-book bot., Ed. 1, 184. 1845. Type. No specimens were directly cited in the protologue which evidently apply to what we would now call E. purpureum L. It seems clear that Lamarck intended to include E. purpureum L. in his E. verticillatum var. a, 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. purpureum L. (see Article 7.13 of the Code). [Wiegand and Weatherby (1937) were unable to locate a specimen in Lamarck’s herbarium at P; Cronquist (1990, pers. comm.) was also unable to find a specimen at P, but a specimen was located in the herbarium of Antoine Laurent de Jussieu, cat. no. 8398, bearing the handwritten label “Eupatorium verticillatum Lamk.” In any case, Lamarck’s name falls into synonymy under E. purpureum L.] Eupatorium fusco-rubrum Walter, Fl. Car. 199. 1788. Type. Without locality, date, and collector’s name. Wiegand and Weatherby (1937) identified the type specimen in Walter’s herbarium at BM as E. purpureum L.; Femald and Schubert (1948) also concluded that Walter’s “is. fuscorubrum, no. 733 on p. 46 of the collection, is small E. purpureum L.” Cronquist (pers. comm.) concluded that Walter’s type specimen at BM is ambiguous and had been severely shriveled before being pressed, thus making identification difficult; my examination of the type photo at GH was also inconclusive, but I herewith follow traditional determinations of the type specimen (holotype, BM fide Cronq.!; photo, GH!). Eupatorium falcatum Michx., Fl. Bor.-Amer. 2: 99. 1803. Eupatorium purpureum var. falcatum (Michx.) Britt., Mem. Torrey Bot. Club 5: 312. 1894. Eupatorium purpureum var. angustifolium f. falcatum (Michx.) Voss, Vilm. Blumengartn., Ed. 3, 1: 447. 1894. Type. Ohio, “ad ripas fluviorum Ohio et Scioto,” s.d. Michaux (bearing the handwritten label “Eupatorium No. 76”) (holotype, P fide Cronq.!; photo, GH!). Eupatorium verticillatum Muhl. ex Willd., Sp. pl. 3: 1760. 1804 (non Eupatorium verticillatum Lam., Encycl. 2: 405. 1786). Type. Protologue: “North America.” Without specific locality, date, and collector’s name. There are two sheets (cat. no. 15127) of Eupatorium verticillatum Muhl. ex Willd. at the Willdenow herbarium in Berlin; both sheets were seen at B by Cronquist in 1991, and I have examined corresponding microfiche at NY. Sheet 1 bears an unsigned handwritten notation “lectotype,” and is here formally accepted as such (lectotype, B fide Cronq.!; microfiche, NY!). Eupatorium amoenum Pursh, Fl. Am. Sept. 2: 514. 1814. Eupatorium purpureum var. amoenum (Pursh) A. Gray, Syn. Fl. 1(2): 96. 1884. Eupatorium maculatum var. amoenum (Pursh) Britt., Mem. Torrey Bot. Club 5: 312. 1894. Eupatorium purpureum var. maculatum f. amoenum (Pursh) Voss, Vilm. Blumengartn., Ed. 3, 1: 447. 1894. Eupatorium trifoliatum var. amoenum (Pursh) Farw., Rep. Michigan Acad. Sci. 20: 191. 1918 [1919]. Type. Protologue: “On the New Jersey mountains.” Without specific locality, date, and collector’s name [holotype, not seen; by description = E. purpureum (search at PH and inquiry to other major herbaria failed to locate the type; Wiegand and Weatherby (1937) were also unable to locate the type)]. Eupatorium purpureum var. ß album Barratt, Eupatoria verticillata no. 3 (see Fig. 31). 1841. Type. Protologue: “In dry woods and hillsides, in rocky places.” Without specific locality, date, and collector’s name [holotype, not seen; by description = E. purpureum (search at NY and inquiry to other major herbaria failed to locate the type; Grimes and Keller (1982) did not include E. purpureum var. album Barratt in the list of type specimens in Barratt’s herbarium)]. Eupatorium purpureum var. yovatum A. Wood, Class-book bot., Ed. 1, 184. 1845. Type. Not cited in protologue. [holotype, not seen; by description = E. purpureum (search at NY and inquiry to other major herbaria failed to locate the type).] Eupatorium harnedii Steele ex Harned, Wildflowers Alleghenies 501. 1931. Type. United States. Maryland. Without specific locality, Oakland, Sep 1909, Harned s.n. (holotype, US!). Eupatorium purpureum f. depressum Jennings, Castanea 7: 47. 1942. Type. United States. Pennsylvania. Allegheny Co.: Partly shaded lower slope near mouth of Falls Run, Glenshaw, 15 Aug 1918, Jennings s.n. (holotype, CM!). Eupatorium purpureum f. laciniatum Jennings, Castanea 7: 47. 1942. Type. United States. Pennsylvania. Allegheny Co.: Shaded floodplain, rocky soil, upper part of Falls Run Ravine, Glenshaw, 15 Aug 1918, Jennings s.n. (holotype, CM!). Eupatorium purpureum f. decolor Seymour, Fl. Vermont, Ed. 4, 344. 1969. Type. United States. Massachusetts. Worcester Co.: Without specific locality, Worcester, 9 Aug 1925, Bemis s.n. (holotype, GH!; isotype, NEBC!). Eupatorium purpureum L. (Figs. 29 «fe 30) is a morphologically variable species. Historically, more than a dozen infraspecific taxa have been proposed, based largely upon differences in leaf shape. One such taxon, E. purpureum var. amoenum, has been widely accepted by taxonomists and was recognized by Wiegand and Weatherby (1937) in their landmark treatment of section Verticillata. Subsequently, var. amoenum has received little taxonomic attention. Eupatorium amoenum was based on extremely depauperate plants and described by Pursh (1814) as a small, attenuate plant with chiefly opposite leaves and a small inflorescence with few heads. Each head contained only 3-5 flowers. No geographic isolation separated var. amoenum from var. purpureum. Eupatorium amoenum appears distinctive in the field (see Fig. 5), but living plants transplanted by the author (from near the type locality in northwestern New Jersey to a garden in New York) grew into ordinary small plants of the widespread and variable species E. purpureum. After two growing seasons in the garden, the small attenuate plants grew into robust plants, well within the morphological limits of E. purpureum (Fig. 6). It was concluded that E. amoenum represented a depauperate shade form of E. purpureum and does not warrant taxonomic recognition. There may have been some ecotypic selection in the wild, but the morphologic expression is increased by the direct effect of the environment. Similar cases have been documented for Erigeron provancheri (Cronquist, 1947, 1988) and Calopogon tuberosus var. latifolius (Catling & Lucas, 1987). In north central United States, plants with densely and persistently pubescent abaxial leaf surfaces occur sporadically, and have been formally recognized as a distinct species (Rydberg, 1931). These plants, however, are not consistently distinguishable from E. pur- pureum by any characters other than leaf pubescence. Both taxa occur in similar habitats and are only weakly differentiated geographically. In view of the overall similarities to E. purpureum, Rydberg’s species was recognized as a taxonomic variety by Lamont (1990b). The two varieties may be distinguished as follows: 1. Abaxial leaf surface glabrous or nearly so, sometimes sparsely pubescent along the major veins; S New Hampshire to N Florida, west to SE Minnesota, Iowa, and E Oklahoma var. purpureum 1. Abaxial leaf surface densely and persistently puberulent to villose throughout; S Minnesota, Iowa, and NE Kansas to S Wisconsin, N Illinois, and N Missouri var. holzingeri