|
|
|
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.
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:
|
|
Small –
|
plant under 6 inches (15 cm) in height, usually ankle high; nut grass, menehune grass (both are sedges, not grasses).
|
|
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 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 Guam. That is, plants are either native or not native (= alien, introduced) to Guam, 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 Micronesia or the Marianas and 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 50 sedge species found on Guam (or 0n other islands in the Marianas), 25 species are considered indigenous and the remaining as introduced species (Raulerson, 2006).
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):
[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.
|
|
