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CPIE Notebook Project - Grasses and Sedges of Hawai‘i Grass Key – Page 1

Key to Family Poaceae

The key to grasses extant in the Hawaiian Islands starts here, although if you are uncertain whether or not the plant you are trying to identify is a true grass or just looks something like a grass, you should start with couplet [1]. Structural details pertinent to grasses are discussed and illustrated at various places in the key; however, some basic descriptive terms are defined on Page iv and these should be understood before starting the key. In this key, items in bold are intended to point out the most salient difference(s) in a couplet, but should not be considered alone until you become experienced with using the key.

leaf blade and sheath picture

Figure 1A. Part of a grass stem (Urochloa distachya) introducing some basic anatomical terms.

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10a bamboo leaves Large or very large grasses with woody stems (called culms); side branches with leaf blades attached by pseudo-petioles. Bamboos.
    ~ Subfamily BAMBUSOIDEAE
pseudo-petiole drawing

Plant size small, medium, large, or maybe very large, but culms never woody. Leaf typically consisting of a blade and a basal part (called a sheath; see Fig. 1A) clasping the stem, but open along a suture (unlike some sedges with closed sheaths, if present).

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11a (4)
Grass unusually robust, large or very large and plant rather coarse in comparison with typical grasses, either reed or cane-like (having a stiff, hollow and jointed stem) and/or forming very large clumps [15]

Plant otherwise; size may be delicate to large, but neither cane-like nor an especially large clump

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12a (11) Leaves linear, with most blades (or at least the lower ones) more than 10X longer than wide [20]

Leaves longer than wide, but not linear, generally only about 6 times (or less) longer than wide

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13a (12) Leaves heavy, narrow elliptic, 2 to 3 inches (up to 9 cm) wide and 5 or 6X longer than wide; parallel veins forming prominent ridges on upper leaf surface. { Clump-forming, medium size grass found in lowland, mesic or wet forests and along streams. Palmgrass (for its resemblance to palm seedlings). Fig. 1D. [NAT]
    Setaria palmifolia (J. König) Stapf
Figure 1D. Palmgrass
  (Setaria palmifolia)
  in flower.


leaves of basketgrass Leaves 1 to nearly 6 in (2-15 cm) long, usually 1/2 in (1 cm) to 1 in (2.5 cm) across, surface wavy (Fig. 1E). { Sprawling grasses common to abundant in shaded locations.

Figure 1E (left). Leaves of basketgrass, Oplismenus hirtellus

Figure 1F (below). Flowering head of O. hirtellus with awned spikelets arranged on racemes.

Flower head of basketgrass

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14a (13) Spikelets (compact cluster of flowers on a lateral stem, see Page 4) on lowest raceme no more than 3/16 in (4 mm) apart. Leaves to nearly 4 in (5-10 cm) long, usually about 1/2 in (1 cm) but less than 3/4 in (2 cm) across (Fig. 1D). { Small, sprawling grasses common to abundant on forest floors in lowland mesic forests. Basketgrass or hohono kukui. (Figs. 1E, 1F) [NAT]
    Oplismenus hirtellus (L.) P. Beauv.

Spikelets on lowest raceme from 3/16 to 1/2 in (4 to 12 mm) apart. Leaves 1 to 6 in (2-15 cm) long, about 1/2 in (1 cm) to 1 in (2.5 cm) across. { Small, sprawling grasses common on forest floors in mesic forests above 800 ft (245 m) elevation. [NAT]

    Oplismenus compositus (L.) P. Beauv.

ToC TABLE of CONTENTS  Basic Grass Description GRASS BASICS  Grass Key Introduction INTRODUCTION  Key to Lawn Grasses LAWN GRASSES  AECOS AECOS, Inc.

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