Flora of North America species comparison

Species ca. 77 (17 in the flora).

The species of 7d. Schoenoplectus sect. Supini produce two morphologically different types of achenes. They have solitary, pistillate (amphicarpic) flowers enclosed in basal leaf sheaths in addition to the terminal inflorescences on the culms. In amphicarpic flowers perianth bristles are usually absent, when present, 1–2, caducous, and sparsely spinulose; the styles are (2–)3-fid, greatly elongated, stigmas are exserted from sheath orifices; achenes are larger than those found in normal spikelets, and their shape and surface sculpturing are different (A. E. Schuyler 1969; J. Raynal 1976; J. Browning 1992).

Schoenoplectus includes some difficult species complexes, each with different ranges outside of North America, that are discussed under the first species in each complex. The four sections recognized here were delineated by S. G. Smith and E. Hayasaka (2001). About ten species from eastern Asia and Africa have not yet been assigned to a section.

Schoenoplectus californicus and members of the S. lacustris and S. pungens complexes are often ecologically dominant in wetlands, where they provide valuable food and habitat for waterfowl and other animals. In North America their culms are used, mostly historically, for making mats, baskets, chair seats, houses, boats, and other objects. Some species are cultivated as ornamentals. Indicator boxes for weediness are marked here on the basis of the status listed under Scripus.

Users of this treatment should note the following features: colors of unripe achenes, even when they appear to be mature, are usually much paler than ripe achenes; lengths of achenes include beak; lengths of scales include awn; spikelets usually elongate during flowering; and culm thicknesses refer to the middle third of culm.

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

Varieties 3 (3 in the flora).

Plants of Schoenoplectus smithii with perianth bristles are easily disinguished from S. purshianus by the uniformly slender bristles in S. smithii; plants without bristles may be identified using the achene characters as indicated in the key. In addition, in S. smithii the receptacle collar is relatively small, the achenes are usually widest distal to the middle, the summit is often subtruncate, the adaxial face is often plane, the abaxial face is without a central bulge and sometimes has a distinct narrow angle, and when mature the surface has fine longitudinal ridges. In contrast, in S. purshianus the receptacle collar is relatively large, the achenes are usually widest at the middle, the summit is usually rounded, the adaxial face is nearly always convex, the abaxial face has a distinct central bulge and never a narrow angle, and the surface lacks fine longitudinal ridges.

The eastern Asian Scirpus komarovii Roshevitz [= Schoenoplectus komarovii (Roshevitz) Soják] was treated as Scirpus smithii var. leiocarpus (Komarov) T. Koyama (= Schoenoplectus smithii subsp. leiocarpus Soják) by T. Koyama (1962b); it is better to treat S. komarovii as a distinct Asian species and S. smithii as restricted to North America pending further research (S. G. Smith and E. Hayasaka 2002).

The varieties of Scirpus smithii were reduced to S. smithii forma setosus (Fernald) Fernald and S. smithii A. Gray forma levisetus (Fassett) Fernald (M. L. Fernald 1942). It seems better to treat those taxa as ecotypic varieties following W. R. Ferren Jr. and A. E. Schuyler (1980) because they reportedly grow in different habitats (S. G. Smith and E. Hayasaka 2002) and thus may be valuable as ecologic indicators. The varieties are undoubtedly more widely distributed than given here; distributions were based on specimens I have seen and reports by A. E. Schuyler (1972) and W. R. Ferren Jr. and A. E. Schuyler (1980).

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