CYPERACEAE (Sedge Family)

Plants annual or perennial, sometimes with rhizomes and/or tuberous thickenings, monoecious or with perfect flowers. Aerial stems circular in cross-section or often 3-angled. Leaves basal and/or alternate, often noticeably 3-ranked, grasslike, parallel-veined, the bases strongly sheathing, the sheaths almost always closed (fused around the stem all or most of the way to the summit), sometimes with a ligule on the inner (upper) surface at the tip, the leaf blades sometimes lacking or highly reduced. Basic units of inflorescences spikelets or spikes (see discussion in the introductory portion of the Carex treatment), these 1 to many, terminal and/or axillary (sometimes basal), arranged into panicles, headlike clusters, or umbels that are often subtended by 1 or more leaflike (or less commonly stemlike or scalelike) bracts. Individual flowers (florets) of a spikelet or spike subtended by scalelike bracts (referred to as scales by most botanists and in this treatment). Perianth absent or reduced to 1–6 (rarely more) bristles or small scales attached below the ovary. Stamens 1–3. Pistil 1, naked or enclosed in a saclike perigynium in Carex. Style 1, branched into 2–3 stigmas at the tip, sometimes persistent at the tip of the fruit as a beak of the same color and texture as the fruit, or as a conical or triangular tubercle that differs in texture and/or color from the main body of the fruit and is separated from it by a line or constriction. Ovule 1 per floret. Fruits achenes. Eighty to 115 genera, 3,500–4,500 species, worldwide.

The Cyperaceae are a large and taxonomically difficult family that still requires detailed taxonomic study on a worldwide basis. Generic limits for many of the groups are hotly debated by specialists, which has resulted in a confusing array of generic transfers in the literature, and often markedly different treatments of the same species groups in floristic manuals covering regions in North America, Europe, Africa, and elsewhere. The treatment below generally follows the generic classification of Bruhl (1995) and accepts many of the recent generic reassessments. However, Cyperus is treated in the relatively broad, traditional fashion (see the treatment of Cyperus for further discussion).

Determination of genus and species for a specimen in this family requires patience and detailed observations using a hand lens or dissecting microscope. Collectors should note that rootstocks and mature fruits usually are necessary for accurate determinations. Vegetative or flowering plants of Cyperaceae generally should be avoided. In a few cases, determinations are aided by observation of both fertile and vegetative shoots and their respective leaf arrangements.

The determination of annual vs. perennial growth form is important for keying plants of most genera of Cyperaceae, but this can be difficult to establish for some plants. In general, annual species have “soft bases” that can usually be pulled from the ground with their roots relatively intact and show no evidence of rhizomes, tuberous root thickenings, or previous years’ stem or leaf bases. Perennials have “hard bases” that are frequently (but not always) difficult to pull up with intact rootstocks, often have rhizomes, tuberous roots, or otherwise thickened rootstocks, and usually have remnants of previous years’ stem and/or leaf bases.