Flora of North America species comparison

Three varieties of Schoenoplectus pungens (under Scirpus americanus) were recognized for North America by T. Koyama (1963), and three more or less equivalent varieties were recognized by S. G. Smith (1995). These varieties are described informally and illustrated here but not formally recognized because their morphologic delimitation should be evaluated and their exact ranges are still uncertain.

Schoenoplectus pungens (Vahl) Palla var. pungens has brown to straw-colored spikelet scales, bifid styles, and lenticular achenes. It is the only variety that occurs in Europe and North America. In North America, it extends from the Atlantic Coast to Saskatoon and is reported from Arkansas, Kansas, Louisiana, Minnesota, and Missouri.

Schoenoplectus pungens (Vahl) Palla var. longispicatus (Britton) S. G. Smith has bright orange to reddish (or purplish) brown or often stramineus and lineolate-spotted spikelet scales, trifid styles, and trigonous to lenticular achenes. Endemic to the flora area, variety longispicatus occurs in western North America, except Pacific Coast, east to Saskatoon, Manitoba, and Ontario, along the north shore of Lake Superior, south to Iowa, Minnesota, western Wisconsin, Missouri, and southern Mississippi.

Schoenoplectus pungens (Vahl) Palla var. badius (J. Presl & C. Presl) S. G. Smith has uniformly dark chestnut spikelet scales, trifid styles 3-fid, and trigonous or thickly biconvex achenes. In North America, variety badius occurs along the Pacific Coast (to slightly inland) from British Columbia south to California. Outside the flora area it occurs in Baja California, Mexico, temperate South America, Australia, including Tasmania, and New Zealand.

The name Scirpus americanus [subsp. monophyllus (J. Presl & C. Presl) T. Koyama] var. monophyllus was misapplied to Schoenoplectus pungens var. badius (T. Koyama 1963). The type of the basionym Scirpus monophyllus J. Presl & C. Presl from Peru belongs to Schoenoplectus americanus (S. G. Smith 1995).

Schoenoplectus americanus, S. pungens, and S. deltarum belong to the small “Scirpus americanus complex” T. Koyama (1963), in which the species are sometimes difficult to delimit. Schoenoplectus pungens was long known incorrectly as S. americanus Persoon; the type of that name is conspecific with plants formerly treated as S. olneyi A. Gray (A. E. Schuyler 1974). Putative Schoenoplectus pungens × S. americanus hybrids [= S. ×contortus (Eames) S. G. Smith] are locally common. 2n = ca. 86–128.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Varieties 2 (2 in the flora).

Culms of Schoenoplectus purshianus have been described erroneously as trigonous (e.g., M. L. Fernald 1950). Schoenoplectus purshianus is widely confused with S. smithii; they are clearly distinct (M. Blondeau et al. 1996; S. G. Smith and E. Hayasaka 2002). Some authors (A. A. Beetle 1942b; H. A. Gleason 1952; H. A. Gleason and A. Cronquist 1963; E. G. Voss 1972–1996) have placed S. purshianus (as Scirpus) in synonymy under Schoenoplectus smithii, and most published distributions are erroneous. The taxonomic confusion is because of the subtle nature of the diagnostic characteristics of achenes and perianth bristles, the occurrence in both species of plants with or without bristles, and overlapping involucral bract lengths and frequency of divergence. No intermediates are known; although the two species occasionally grow together they are not known to hybridize. Close examination of the perianth bristles and achenes of S. purshianus and S. smithii reveals taxonomically useful but overlooked differences as stated in the key and summarized under S. smithii.

Schoenoplectus purshianus has also been confused with its close relatives in sect. Actaegeton: Schoenoplectus juncoides (Roxburgh) Palla, S. hotarui (Ohwi) Holub, and Scirpus rockii Kükenthal, which belong to the difficult “Scirpus juncoides complex” of eastern Asia, the Pacific islands, and eastern North America; Schoenoplectus purshianus should be treated as a distinct North American species pending further research (S. G. Smith and E. Hayasaka 2002).

The name Scirpus erectus Poiret has been widely misapplied to members of that complex (see 17. Schoenoplectus erectus). The names Scirpus smithii var. williamsii (Fernald) Beetle, S. juncoides Roxburgh var. williamsii (Fernald) T. Koyama, and Schoenoplectus smithii subsp. williamsii (Fernald) Soják were misapplied by their authors to both S. purshianus var. purshianus and S. purshianus var. williamsii.

Schoenoplectus purshianus var. williamsii in recent years has been treated as Scirpus purshianus forma williamsii (Fernald) Fernald. It seems better to treat the taxon as a variety rather than a form, pending further research, because it reportedly occurs in habitats with more water-level fluctuation than S. purshianus var. purshianus (A. E. Schuyler 1972; S. G. Smith and E. Hayasaka 2002) and thus may be useful as an ecologic indicator, and because form status suggests that the taxon is trivial.

(Discussion copyrighted by Flora of North America; reprinted with permission.)