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A DICHOTOMOUS KEY
TO THE GRASSES, SEDGES, AND RUSHES
OF THE HAWAIIAN ISLANDS
With Links to A Key to Aquatic Plants in Hawai‘i
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[NOTE: THREE CHOICES HERE]
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1a
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Plant generally grass-like: herbaceous, with leaves linear, very many times longer than wide, leaf veins parallel; if blades not exactly linear, veins are still parallel; OR plant a green stem without obvious leaf-like structures, or these small and sessile (leaf lacking a petiole or leaf-stem), clasping the stem. Flower heads may be conspicuous, but individual flowers are small and usually mature to some shade of brown or yellow (usually green when immature).
~ Class LILIOPSIDA (MONOCOTS, in part)
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[2]
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1b
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Plant somewhat "grass-like" with tall, woody, hollow (jointed) stems or culms; leaves not clasping but attached to side branches by pseudo-petioles. Rarely producing flowers in Hawai‘i. Bamboos
~ Class LILIOPSIDA, Family POACEAE, Subfamily Bambusoideae
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[24] 
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1c
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Plant not grass-like: may be herbaceous or may be woody, but leaves at most only 5 or 6 times longer than broad; leaf veins arising from a central axis or radiating from a central point. Flowers variable, but many species with conspicuously colored or otherwise showy petals. Other aquatic monocots
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[107]
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2a
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(1) |
Plant mostly a soft, green, vertical stem (called a culm), without leaves, or leaves present only as basal sheaths without blades, or blades inconspicuous. Flower head or heads at or near tip of stem, in some cases, with a conspicuous bract subtending (found directly below) the flower head. Certain rushes
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[10]
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2b
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Stem, if soft, green, and upright, then clasped by one or more long, narrow leaves or with a basal rosette of narrow leaves; OR stem otherwise (creeping, branching)
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[3]
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3a
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(2)
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Leaves in two ranks (distichous: looking down on the culm, leaves come off on two sides). Stems usually hollow except at nodes. Clasping part of leaf below blade open along a vertical seam
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[4]
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3b
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Leaves in three ranks: looking down on the culm, leaves come off on three sides; sheathing part of leaf closed. Stem usually solid, usually trigonous (three-sided), but exceptions exist. Sedges
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[15]
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4a
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(3)
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 Flowers arranged in a dense(and solitary) spike (1.5 - 3 cm diameter) arising above flattened, spongy, pale green leaves, lacking a midrib. Cattails
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[98]
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4b
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Flowers arranged in various ways, usually in several to many spikelets. Leaves linear, pale to dark green, but not fleshy or spongy, most often with a midrib that is prominent on upper or lower leaf surface. Grasses
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[11]
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