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).


[GENUS FIMBRISTYLUS]

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

[31]
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]
31b

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

[33]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[NOTE: THREE CHOICES HERE]
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]
33b

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.

[34]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.)
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