CPIE Notebook Project - Grasses and Sedges of Hawai‘i Sedge Key – Page 32

Key to Genus Fimbristylis

Sedges in the genus Fimbristlis are small to medium-size plants found in wetlands and fields, with one (F. cymosa) a native, coastal inhabitant. These sedges Fimbristlis cymosa resemble generally the more diverse, so-called "flat sedges" (Genus Cyperus), except the spikelets are spindle-shaped (round in cross-section instead of compressed), the floral bracts arranged spirally on the rachis.

The genus in Hawai‘i is represented by 8 taxa (7 recognized species, one with 2 subspecies); three of the species are native sedges (Wagner, et al., 1990); five are found in wetlands (Erickson & Puttock, 2006). One Fimbristilis is endemic and two are indigenous to the Islands.

Figure 32A. Native mau‘u ‘aki‘aki (Fimbristylis cymosa umbellato-capitata).


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30a (18) Spikelets longer than wide, tapering towards the top. Leaves variable. Styles either flattened or thread-like

30b Fimbristylis littoralisSpikelets ovoid to spherical in shape, about as long as wide. Leaves long and narrow (1-2 mm x 15-40 cm). Styles of flowers thread-like. Achene about 1 mm long [NAT] [OBL]
    Fimbristylis littoralis Gaud.
31a (30) Inflorescence of several filiform rays up to 1 in (3 cm) long, each terminated in a single spikelet or at most by a pair. Leaves few, narrow (1/16 in [1 mm] or less), inrolled. { Species having very limited distributions [32]

Inflorescence more complex with numerous spikelets arrayed digitally or spicately on multiple branches or dense heads. Leaves variable. { Perennial apecies widespread across the Islands

32a (31) Infloresence comprising 3 to 7 filiform rays, each terminating in but a single pale spikelet, 2.5-5 mm long. { Small annual in wet places on the Islands of Hawai‘i and Kaua‘i only [NAT] [FACW]
    Fimbristylis aestivalis (Retz.) Vahl
32b Inflorescence of 1 to 4 rays, each teminating in an orange-brown spikelet, or rarely with a second, lower spikelet, these 5-14 mm long. { Small short-lived perennial in wet places in Hilo, Hawai‘i only [NAT] [FACW]
    Fimbristylis schoenoides (Retz.) Vahl
32c Inflorescence of several rays, each teminating in a two-tone brown spikelet, or rarely with a pair of spikelets, these 5-9 mm long. { Small perennial, rare as a pioneer on pahoehoe on Kilauea, Hawai‘i only [END] [UPL]
    Fimbristylis hawaiiensis Hillebr.
33a (31) Culms erect, up to 2 or 3 ft (1 m) tall. Spikelets 1/8 in up to 1/2 in (4 to 14 mm) long. Flower style flattened, the margins distinctly fimbriate. Achene over 1 mm in length. [35]

Plant a low tuft of often dark leaves, with stiff, blunt tipped blades up to 1/8-in wide and culms under 2 ft (60 cm) tall. Inflorescence either simple or compound, or condensed (headlike). Spikelets 3 to 6 mm long. Style flattened hardly at all, margins not fimbriate. Achene 1 mm or less in length. { Two widely spread subspecies growing in coastal sites (see Figure D) starting not far inland from the normal wash of waves. mau‘u ‘aki‘aki. Fimbristylis cymosa R. Br.

34a (33) Inflorescence branches (rays) 1 to 2 in (2-5 cm) long; spikelets in clusters of 2 to 5, or solitary. mau‘u ‘aki‘aki [IND] [FACU]
    Fimbristylis cymosa spathacea (Roth) T. Koyama
34b Inflorescence typically a single teminal head or sometimes with 2 or three smaller heads (see Fig. 32A). Rays (if present) under 1 in (1-2 cm) in length. mau‘u ‘aki‘aki [IND] [FACU]
    Fimbristylis cymosa umbellato-capitata (Hillebr.) T. Koyama
35a (33) Culm trigonous. Spikelets 1 to 3 terminating ascending branches 1 in to 4 in (2-10 cm) long; spikelets 1/8 to 1/3 in (4 - 8 mm) long and pale reddish brown. Floral bracts without hairs. { Found mostly in upland areas of moist soil. [IND] [FAC]
    Fimbristylis dichotoma (L.) Vahl.
35b Culm rounded (terete)but flattened near tip, up to 3 ft (1 m) tall. Spikelets on short, mostly simple branches; spikelets 1/4 to 1/2 in long (6 - 12 mm) and dark reddish brown. Floral bracts with silvery hairs at least at tips. { Found mostly in wetlands. West Indian fimbry [NAT] [OBL]
    Fimbristylis ferruginea (L.) Vahl

Selected synonyms for species included above:

Fimbristylis miliacea (L.) Vahl. (= F. littoralis Gaud.)

Table of Contents TABLE OF CONTENTS  To grass inflorescence types INFLORESCENCE TYPES  Grass Key Introduction INTRODUCTION  AECOS AECOS, Inc.

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