Cyperaceae – Sedge Family
To the untrained eye, Sedges may appear to be grasses, but these graminoids are their own distinctive family, playing an important role in wetland ecosystems. Cyperaceae is a large family, with 104 genera and about 5000 species with worldwide distribution.[1] Three genera occur in Willamette Valley Wetlands – Carex (true sedges), Eleocharis (spike rushes), and Scirpus (bulrushes). Unlike grasses (Poaceae) though, Cyperaceae lack nodes, or joints, along their stem, and their leaves are spirally arranged in three ranks. Instead, these herbaceous perennials have long, (usually) triangularly three sided, simple leaves, with parallel veins.[2] Inflorescences consist of terminal “sedge spikes” that vary in overall arrangement of many individual scales or glumes, each subtending an individualized flower.[3] Flowers lack sepals and petals, instead having scale like tepals with three stamens and superior ovaries that are wind pollinated. These plants produce small, protein-rich nutlets that are commonly grazed by waterfowl and are a common source of nesting habitat.
This family does not have a traditional economic human use. However, these graminoids provide valuable wetland ecosystem services such as slowing and filtering water, or providing food and shelter to many types of water fowl. Some well-known sedges include water chestnuts (Eleocharis dulcis) and papyrus (Cyperus papyrus), from which paper was famously made from in Ancient Egypt (ref).
Carex unilateralis – One sided sedge
Species Code: CAUN
Habit: Densely cespitose (growing in a clump) perennial graminoid, 35 to 75 cm tall, yellowish green, flat stems, with golden/brown compact inflorescence siting in axil of unequal bracts.[4]
Stems: Round stemmed sedge species, 35 to 75 cm tall, lead to inflorescence.
Leaves: Flat, long leaves are 2-5 mm wide and lower leaves are reduced to sheaths.[5]
Inflorescence: These wind pollinated flowers lack showy corolla parts. Inflorescences are comprised of many flattened green/gold to brown scales clustered into a dense head about 1.4 to 2.5 cm long and 9 to 17 mm wide.[6] Flower head comprised of four to six male and female flower spikes bunched together at the axil of two very uneven bracts giving the impression that the flower is asymmetrically angled to just one side of the sedge – giving this plant its name.xxi The top bract is much longer than the flower head (5 to 15 cm long) and looks like a continuation of the plant stem.[7] Other bracts are shorter, growing laterally from the base of the inflorescence.
Fruits: Flat achenes are 1-2 mm long, beginning as a greenish color with light brown streaks, becoming increasingly warm brown with maturity. In Carex a perigynium, or a hard membrane surrounds the pistil. The lance-shaped perigynium is widest in the middle, tapering at both ends to a sharp beak.
Ecology: FACW, Facultative Wetland species common in wetland prairies, vernal pools, lacustrine/palustrine margins, freshwater marshes and ditches that are seasonally flooded or semi- permanently saturated throughout the year.
Notes: Without careful examination, Carex unilateralis can be confused with a number of other sedges, but is recognized by it’s one sided inflorescence, two short lateral bracts, and long vertical bract extending above the seed clusters. East of the Cascades, Slender-beaked sedge (Carex arthostachya) has a similarly erect inflorescence that sits directly on top of the culm.[8] In Willamette Valley Wetland Prairies, commonly associated species are Carex leporina (Eggbract sedge), Carex densa (Dense sedge), Deschampsia cespitosa (Tufted hairgrass), and various Juncus spp.xxxiii C. unilateralis requires cold stratification in order for seeds to germinate well, therefore restoration practitioners tend to put out these seeds in fall in anticipation of winter temperatures.[9] Controlled low-intensity burning helps control these often dominant plants where below-ground roots survive fire but above-ground biomass (and therefore, seed development) experiences decrease 1-2 years following burns.[10] C. unilateralis is a key food source for waterfowl, migrating shorebirds overwintering in the Willamette Valley, songbirds, beavers, muskrats, black tailed deer and other small mammals.[11]
Carex densa – Dense Sedge
Carex feta – Green Sheath Sedge
Carex leporina
© 2001 Wilbur Bluhm
Carex obnupta – Slough Sedge
Carex stipata var. stipata – Sawbeak Sedge
Carex tumulicola – Foothill Sedge
Eleocharis acicularis – Needle Spikerush
©2014 Gerald D. Carr
Eleocharis obtusa – Common Spikerush
Eleocharis palustris – Creeping Spikerush
© 2012 Bruce Neil Newhouse
[1] Elpel, T. J., Botany in a Day: The Patterns Method of Plant Identification. HOPS Press, 2004. 160
[2] Simpson, M., Plant Systematics 2nd ed. Academic Press, Burlington, MA. 2010. 250
[3] Elpel, T. J., Botany in a Day: The Patterns Method of Plant Identification. HOPS Press, 2004. 160
[4] Wilson, Barbara, et al. Field Guide of the Sedges of the Pacific Northwest. Oregon State University Press, 2008. 380.
[5] Cooke, Sarah Spear, Ed. A Field Guide to the Common Wetland Plants of Western Washington and Northwestern Oregon. Seattle Audubon Society. 1997. 284.
[6] Wilson 380
[7] Wilson 380
[8] Wilson 380
[9] Krueger, J., Bois, S., Kaye, T., Steeck, D., Taylor, T., (2014). Practical Guidelines for Wetland Prairie Restoration in the Willamette Valley, Oregon: Field Tested Methods and Techniques. Lane Council of Governments, Institute for Applied Ecology, City of Eugene. 2014.
[10] Krueger, J., Bois, S., Kaye, T., Steeck, D., Taylor, T., (2014). Practical Guidelines for Wetland Prairie Restoration in the Willamette Valley, Oregon: Field Tested Methods and Techniques. Lane Council of Governments, Institute for Applied Ecology, City of Eugene. 2014.
[11] Wilson, Barbara, et al. Field Guide of the Sedges of the Pacific Northwest. Oregon State University Press, 2008. 380.
