Many structural details concerning sedge identification will be introduced at various places throughout the key. To begin using the key, however, it is important understand several very general terms used here in describing sedges, such as growth form and size.

Growth form or habit in sedges is fairly limited in its diversity, which, as is the case with grasses, suggests that species may be difficult to distinguish from one another without careful consideration of the flowering structure. The basics of sedge habit have been introduced on the previous page (see Figure L): strap-shaped (linear) leaves form a basal rosette from the center of which, arises a culm bearing the flowering structure. In some sedges, leaves are borne along the length of the culm, and there are usually leaves, called bracts, associated with the infloresence. Many other sedges either lack leaves altogether or the leaves are reduced to basal scales (these plants are distinguished as "rushes"). Sedges spread by stolons or rhizomes, the latter growing horizontally underground.

The size achieved by a plant can vary considerably depending upon conditions under which it grows, so realize that the size categories described here (small, medium, and large) are not absolutes but guides to help confirm an identification. As a rule, a particular sedge species will not be larger than the size given, but may be smaller if growing under adverse conditions. Once a sedge plant is in flower, that plant is (within the broad categories used here) about as large as it is going to get. The terms used in the key for sedge plant size are defined as follows:

Growth form and persistence (or duration) are characteristic useful for describing a grass species, somewhat less so for sedges. Many sedges do spread by rhizomes (underground stems) or stolons (a horizontal stem creeping across the ground, rooting at nodes). Others are bunching or clumping, the stem portion remaining short and close to the base.

A sedge may be an annual or a perennial. Annuals are typically small to medium size sedges with short rhizomes. Because of our mild climate, some annuals may persist beyond a year in favorable locations.

Plant Status—By plant status is meant the origin of a species (or subspecies) relative to the Hawaiian archipelago. That is, plants are either native or not native (= alien, introduced) to Hawai‘i, and this information is provided in the key in brackets at the identification couplet. Coding in the key appears as follows:

Of the at least 69 sedge species found in the Hawaiian Islands, 28 species are indigenous and 17 are endemic (Wagner, Herbst, & Sohmer, 1990). None is described as a Polynesian introduction, which seems odd considering that the early Polynesians brought with them kalo (Colocasia esculenta), a wetland plant, the "packing" of which in preparation for the long sea voyage, would seem a very probable source of sedge seeds. On the other hand, migratory birds may have introduced these indigenous species to our wetlands long before arrival of the first Polynesians.

Wetland Status—The U.S. Army Corps of Engineers maintains a list (National Wetland Plant List) relating the indicator status (liklihood) that a plant species will occur in a wetland. Because many sedges in our key are found in wetlands and other wet areas such as streams, the latest (Lichvar & Gillrich, 2011; Lichvar, et al., 2016) wetland status code for the Hawaii region is provided for each species in the key. The species status is defined as follows (USACE, 2016):

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