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A CPIE Notebook Project – Grasses and Sedges of Hawai‘i Page vii

Basic Characteristics of Sedge Plants

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.

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:

Small plant under 6 inches (15 cm) in height, usually ankle high; nut grass, menehune grass.
Medium – plant greater than 0.5 foot and up to 3 feet (0.15 to 1 m) tall: typically between shin and knee high; most sedges.
Large sedge plant typically over 3 feet (1 m) in height up to about 6 feet (2 m); umbrella sedge, giant bulrush.
V. large plant greater than 6 feet or 2 m; Egyptian papyrus, giant bulrush.

Growth form and persistence (or duration) are important characteristic useful for describing a grass species. Grasses are usually distinguishable as one of two basic growth forms: running (spreading by rhizomes or stolons or both) or tufted (bunching or clumping).

A sedge may be an annual or a perennial. Annuals are typoically 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:

    [END] – endemic; a sedge that is native, evolved in the Islands; unique to Hawai‘i;
      not native to any other places in the world.

    [IND] – indigenous; a sedge that is native, arriving in the Islands on its own, but also native to other places.

    [NAT] – naturalized; a sedge alien to the Islands that has naturalized (adapted to the "wild"); NOT native.

    [ORN] – ornamental; a sedge alien to the Islands that is not naturalized; used in landscaping or agriculture.

Of the at least 69 sedege 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.

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, et al., 2016) wetland status code for the Hawaii region is provided for each species in the key. The status is defined as folows (USACE, 2016):

    [OBL] – obligate; plants that always occur in standing water or saturated soil.

    [FACW] – facultative wetland; plants that nearly always occur in areas of prolonged flooding
      or require standing water or saturated soil, but may, rarely, occur in non-wetlands.

    [FAC] – facultative; plants that occur in a variety of environments, including wetland and mesic
      to xeric non-wetlands, but commonly occur in standing water or saturated soils.

    [FACU] – facultative upland; plants that typically occur in mesic and xeric non-wetland environments,
      but may frequently occur in standing water or saturated soil.

    [UPL] – upland plants that rarely occur in water or saturated soil.

© 2016-17 AECOS, Inc. [FILE: Sedge_Info_ii.html] Page vii (About sedges)
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