top of page
CPIE Notebook - Grasses and Sedges of Hawai‘i and Guam Sedge Key – Page 32


Key to Genus Cyperus L.

Cyperus difformis flower heads

Sedges in the Genus Cyperus are sometimes referred to as "flat sedges", alluding to the fact that the spikelets of most species have the glumes 2-ranked along the rachilla, so each spikelet appears laterally compressed or flattened in cross-section. In many species, the spikelets are sub-terete (more or less oval in cross-section).


Figure 32A. Flower heads of Cyperus difformis showing 2-ranked, flattened spikes in congested, globose or half globose, heads.

With perhaps 29 species in Hawai‘i, the Genus Cyperus is the largest in the Family Cyperaceae in the Islands. Some 15 species are common in wetlands (Erickson & Puttock, 2006). Others occur in damp places, fields, and lawns. Raulerson (2006) lists 14 (plus one other possible) species of Cyperus found on Guam. If confirmed, our observation of C. croceus adds yet one more. Note that the genus Cyperus as treated here includes species placed in the genera Mariscus, Pycreus, and Torulinium by other sources (see synonyms listed at bottom of page).


[GENUS CYPERUS]

. .
19a (To last couplet17) Plant a soft (spongy), green, vertical stem (a culm) lacking leaf blades, although basal sheaths without blades may be present and leaf-like bracts directly under the inflorescence may be present near the top of the culm. { Wetland species (FACW and OBL) .. .

[20]
19b Leaf blades (other than involucral bracts) present. Culm clasped by one or more long, narrow leaves (leaves are cauline, attached at points up the culm) OR with a basal rosette of narrow leaves OR with cauline and basal leaves. { Wetland and upland species .. . [23]
~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~
20a (To last couplet11
  &
19)
Large to very large plants, rising from 3 to as much as 15 ft (1 to 5 m) in height. Culms weakly trigonous, from 1/2 to 1 in (1 to 3 cm) in diameter near the base, and terminated by many unequal, arching branches, these each with 3 to 8 secondary branches. Leaf blades absent or (rarely) very short, clasping base of culm. { An ornamental sedge, escaping and naturalizing by offshoots (seeds apparently not produced in Hawai‘i). Egyptian papyrus [HAW - NAT] [OBL]; [GUM - NAT]
    Cyperus papyrus L.
20b Small to large plants, culms generally under 4 ft (1.5 m) in height and under 1/2 in (1 cm) in diameter at the base. Leaf sheaths present, but lacking blades. Culms terminated by flowering spikes, sessile or on short branches, and leafy involucral bracts, which are longer or shorter than the inflorescence (if few, one may appear as an extension of the culm giving appearance that inflorescence is not terminal; see Fig. 32C) .. . [21]
~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~
21a (20) Involucral bracts mostly shorter than inflorescence; OR spikelets sessile on culm with but only one long bract, this extending vertically above the spikelet cluster .. .

[22]
21b Involucral bracts linear, typically long, and 3 or more present .. . [35]
~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~
22a (21) Culms terminated by 50 to 250 rays (branches), superficially resembling the head of a papyrus sedge; however, these branches support clusters of reddish-brown spikelets. Bladeless, dark (reddish brown to purple) leaf sheaths clasp base of weakly trigonous culms that rise between 1 to 3 ft (0.3 to 1.1 m) in height. { An ornamental sedge grown in water gardens, naturalized on Kaua‘i. Dwarf papyrus [HAW - NAT] [OBL]
    Cyperus prolifer Lam.
22b Makaloa at Makalawena

Spikelets sessile and terminal on the culm, from 3 to 30 in number, subtended by several bracts, the longest being rolled and vertical, appearing as a continuation of the culm above the flower head. Culms three-sided. { Plants small to large, 6 in to 3 ft (0.2 - 1 m) in height. Makaloa [HAW - IND] [OBL]

    Cyperus laevigatus L.
Close-up of C. laevigatus spikelets


Figure 32B (above). Makaloa plant at Makalawena.


Figure 32C (right). Close-up of the spikelets of Makaloa. Note vertical bracts that appear as extentions of the culm


Consider somewhat similar Schoenoplectus spp.

~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~
23a (To last couplet17
&
19)
Spikelets arranged in compact, globose heads, typically rather dense (see Fig. 32A); the culm terminating in one to several such heads, heads on rays or sessile .. .

[24]
23b Spikelets arranged otherwise: spikelets in compact clusters, but these NOT globose or oval in shape, typically elongated; OR spikelets generally in clusters of but a few or spaced out along a visible supporting stem (rachis), multiple such stems present and these may be branching and jointed .. . [29]
~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~
24a (23) C. croceus flower head Globose to ovoid heads terminal on culm, with or without several more on rays. Subterete spikelets of two to four florets, 4-8 mm long. Leafy bracts subtending the inflorescence present or absent. { In Hawai‘i, found in somewhat drier areas. [HAW - NAT] [?GUM - NAT]
    Cyperus croceus Vahl

24b (23)

Each spikelet of many (6 or more), closely imbricate florets. Leafy bracts typically present .. .

[25]
~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~
25a (24) Spikelets longer than 6 mm (1/4 in), with 6 to as many as 40 flowers on each .. .

[26]
25b Cyperus difformisCulms 20 to 60 cm tall, sharply trigonal. Spikelets with from 8 to 28 flowers and under 6 mm in length. Spikelets arranged in compact heads, sessile or on rays to 1 cm long. Involucral bracts 2-4, up to 22 cm (9 in) long. Floral bracts (glumes) purple with green margins. ( Common in lowland wetlands [HAW - NAT] [OBL]; [GUM - NAT]
    Cyperus difformis L.
~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~
[NOTE: THREE CHOICES HERE]
26a (25) C. eragrostis on Kauai

Plants between 30 and 90 cm tall. Spikelets in congested globose heads of stacked spikelets; oblong spikelets 6-12 flowered and 5 to 20 mm long, yellowish green to reddish brown. Nut on a short stalk, ellipsoid, and dark brown or black in color. { Hamakua (Hawai‘i Isl.) and possibly Kaua‘i only. [HAW - NAT] [OBL]

    Cyperus eragrostis L.
26b

Plant 20 to 60 cm high. Oblong elliptic spikelets 6 to 18 mm long and 2 to 2.6 mm wide, with 6 to 32 flowers, glumes dark purple to brownish black. Nut on a short stalk, laterally compressed, and dark brown in color. { Hamakua area of Hawai‘i Isl. only. Bloodscale sedge [HAW - NAT] [FACW]

    Cyperus sanguinolentus Vahl.
26c Spikelets yellowish green to reddish brown, the spikelets not in groupings that appear stacked. Nut yellowish, compressed or not. Height usually under 0.5 m .. . [27]
~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~
27a (26) Magnifying Lens Leaves shorter (or sometimes) longer than culm, flat, weakly folded, 1/8 in or less (1.5-3.0 mm) in width. Floral bracts (glumes) not awned. Nut laterally compressed, elliptic in cross-section. Lanceolate spikelets crowded with 8 to 40 flowers, spikelet tips acute. Common in and out of wetlands. C. polystachyos .. .

[28]
27b Leaves longer than culm, stiff, narrow, u-shaped in cross-section (channeled), about 1/8 in (2.5-3.5 mm) wide. Each glume terminating in a very short awn or recurved mucro and having membranous wings (Fig. 32H). Nut trigonous (three-sided in cross-section). { Rare, found typically at edges of wetlands and only on main Hawaiian Islands north of Lana‘i. Pu‘uka‘a. [HAW - END] [FACW][E]
    Cyperus trachysanthos Hook. and Arnott
~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~
28a (27) Yellowish-brown flower heads somewhat lax, with 8 - 26 flowers. { basal leaf blades sometimes exceeding the inflorescence [HAW - IND] [FACW]; [GUM - IND]
    Cyperus polystachyos holosericeus (Link) Koyama
28b Flower heads compact and globose, pale to deep reddish-brown in color and with 10 to 40 flowers per spikelet (see Fig. 30A). [HAW - IND] [FACW]; [GUM - IND]
    Cyperus polystachyos polystachyos Rottb.

Author disagrees with assignment of C. polystachyos in Hawai‘i as FACW; these sedges are common and weedy and should be FAC.

~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~
[NOTE: THREE CHOICES HERE]
29a (23) Spikelets arranged in open digitate clusters, sessile or at the ends of primary and, if present, secondary branches .. . [30]
29b

Flattened or somewhat rounded spikelets arranged more or less loosely around and up the length of primary and secondary branches terminal on the culm; spikelet stem jointed and breaking apart at maturity (Species treated by some in the genus, Mariscus) .. .

[38]
29c

Spikelets in elongated, dense sessile (or on short branches) spikes clustered at the top of the culm. Involucral bracts 2-6, exceeding spikes in length. Spikelets with few florets (less than 4) .. .

[36]
~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~
30a (29) Spikelets dark reddish brown and arranged both digitally at the end of branches and spicately along some branches; each spikelet 1 to 3 cm (1/2 to 1 in) long. Rhizomes thin with globose-ovoid tubers (underground "nuts"). { Common weed in lawns and waste places. Nut grass, kili‘o‘opu. [HAW - NAT] [FACU]; [GUM - NAT] [FAC]
    Cyperus rotundus L.
30b Involucral bracts short and broad. Spikelets light brown and aranged in loose digitate clusters located at the ends of primary and secondary branches; variable in length, each spikelet 1/4 to 1/2 in (5 to 15 mm) long. { Found in wet places. Dwarf papyrus sedge. [HAW - NAT] [FACW]; [?GUM] [OBL]
    Cyperus haspan L.
~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~
32a (29) McCoy grass flowering head Small sedge with filiform leaf blades (thin, thread-like, 1 mm wide or less) and arching, no more than 15 cm (6 or 7 in) long, typically somewhat less, 3 or 4 arising at the base of a somewhat lax flowering culm. Spikes 2 to 6 attached together (digitate) directly at top of culm, subtended by two or more long, filiform involucral bracts. { growing in moist, shaded areas; a lawn weed, spreading by plantlets. McCoy grass, mau‘u hunehune. [HAW - NAT] [FACU]
    Cyperus gracilis R. Br.
32b

Basal leaves not filiform, at least 2 mm wide. Spikelets mostly in loose digitate clusters at the ends of primary and secondary branches, with or without a few other spikelets sessile along some branches. Inflorescence very open with no or only a few involucral bracts, these tending to be not much longer than the flowering head. Spikelet stem not jointed .. .

[33]
~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~
33a (32) Annual or perennial herb to 0.9 m tall, with an acutely trigonous culm. Spikes tapering somewhat towards tips (that is, spikelets become shorter towards the top of the spike); Spikelets flattened, hairy, 0.6 to 1.5 cm long, not jointed, with 8-25 flowers each. { Found only on Kaua‘i. [HAW - NAT] [FACW]
    Cyperus pilosus Vahl

33b Annual or short-lived perennial herb to 1.4 m tall, with a smooth, 3-sided culm. Spikes not tapering towards tips; spikelets flattened, not hairy, 1.0 to 2.5 cm long, and jointed between the 10-25 flowers, breaking apart at maturity forming a corky, winged attachment for the fruit. { Pu‘uka‘a [HAW - IND] [FACW]; [GUM - IND]
    Cyperus odoratus L.
~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~
35a (21) Involucral bracts under inflorescence numerous (up to twenty-two), 6 to 11 in (15-27 cm) long. Culms rising to 4 ft (1.5 m), trigonous, about 0.5 cm in diameter, with a rough surface (scabrous). Flowers 6-30 in spikelets 3-25 mm long. { An ornamental sedge, widely naturalized in streams and marshes. Umbrella sedge [HAW - NAT] [FACW]; [GUM - NAT] [FACW]
    Cyperus involucratus Roxb.
35b Involucral bracts under inflorescence three to seven in number. Spikes 2 to 5 cm (1 to 2 in) in length with 6-15 spikelets, these loosely arranged to more imbricate further out on the spike. Spikelets oval, 6 mm long, yellowish with green veins; a tiny mucro at tip of the glumes. { Ricefield flatsedge [GUM - IND] [FACW]
    Cyperus iria L.
~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~
36a (29) Plant robust, to 1 m (3 ft) tall. Numerous dense spikes distinctly arranged on rays (1 to 16 cm long) at top of culm: a much elongated vertical spike (to about 30 mm long) is accompanied by several smaller subglobose spikes, at least two of these angled obliquely downward. Involucral bracts elongate. Spikelets 4-6 mm (to 1/4 in) long. { This species easily recognized by the form and arrangement of the spikes [GUM - NAT] [FAC]
    Cyperus ligularis L.
36b Spikes either sessile or on branches, but inflorescence not as described above .. . [37]
~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~
37a (36) Spikes clustered at the top of the culm, essentially sessile; spikes up to 1.5 cm long. Involucral bracts 2-4. Spikelets with less than 4 florets. { Tufted perennial with a short, thick rhizome. Maui County. [HAW - NAT]
    Cyperus aggregatus (Willd.) Endl.
37b Inflorescence simple but spikes not sessile; instead clustered at the ends of narrow branches (rays) and 2 to 4 cm long (in some cases, much longer). [40]
~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~
38a (29) Spikelets with fewer than 8 flowers each, flattened or sub-terete (flattened only a little) .. .

[39]
38b Culms 40-120 cm tall, acutely trigonous, sides slightly concave. Leaves 3-5 per culm, about as long the culm. Spikes 2-6 cm long, mostly unbranched; spikelets arrayed evenly up length of rachis, each flattened spikelet with 8 to 25 flowers. Involucral bracts longer than the inflorescence, the longest 35 cm (1 ft) long. { Rare (an endangered species) in open sites in mesic forests up to 1200 m (3900 ft) elevation [HAW - END]
    Cyperus pennatiformis Kukenth
~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~
39a (38) Cyperus javanicus (Guam)Coarse perennial with a stiff, roughened, 3-sided culm, 40-110 cm tall. Leaves numerous, most longer than culm. Spikelets flattened, to 6 mm long, with 5-7 flowers each. { Common in a range of environments from uplands to marshes. ‘ahu‘awa [HAW - IND] [FACW]; [GUM - IND] [FAC]
    Cyperus javanicus Houtt.
39b

Perennial herb to 0.5 m tall (1.5 ft), with a smooth, 3-sided culm. Leaves numerous, most as long as or slightly longer than the culm. Spikelets sub-terete, to 1.0 cm long, with 3-4 flowers each. { In moist, disturbed environments on Kaua‘i and possibly O‘ahu. Meyen's sedge [HAW - NAT] [FACW]; [?GUM] [FACW]

    Cyperus meyenianus Kunth
~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~
40a (37) Tufted perennial with culms to about 0.5 m tall. Leaves 10-20 cm long. Spikes cylindric, clustered on branches about equal to (or a little shorter than) the spikes; spikelets spreading at right angles to the rachis. Spikes up to 12 cm long, though typically much shorter. Involucral bracts 2-6. Spikelets 3-4 mm (1/8 in) long, with 1-3 florets (mostly 1). { Rare in Hawai‘i; known only from Lāna‘i and Kawaihae, Hawai‘i Island [HAW - NAT] [FAC]; [GUM - IND]
    Cyperus cyperoides (L.) Kuntze
40b Tufted perennial with one or few culms, 0.2-0.7 m tall, smooth and trigonous. Leaves several, shorter than culm; sheaths pale green tinged purplish pink. Inflorescence simple, open or head-like; rays 6-10, 0-5 cm long. Spikes 5-10, each 2-2.5 cm (1 in) long, tapering to the apex. Involucral bracts 4-10, some longer than inflorescence. Spikelets 4.5 mm long, 2-3 flowered. { Plants in Hawai‘i and Guam smaller, with heads less congested than mainland Asia populations. Found in open grassy sites; in Hawai‘i reported from Kaua‘i and Moloka‘i [HAW - NAT] [FACU]; [GUM - IND]
    Cyperus cyperinus (Retz.) Suringar


Selected synonyms for species included or expected on this page:

    Cyperus alternifolius L. (= C. involucratus Roxb.)
    Cyperus brevifolius see Kyllinga brevifolia Rottb.
    Cyperus halpan L. is a less-used name for C. haspan L.
    Cyperus kyllingia Endl. see Kyllinga mindorensis Steud.
    Pycreus polystachyos (Rottb.) P. Beauv. (= C. polystachyos Rottb.)
    Mariscus cyperinus (Retz.) Vahl (= C. cyperinus Retz.)
    Mariscus javanicus (Houtt.) Merr. & Metcalfe (= C. javanicus Houtt.)
    Mariscus meyenianus (Kunth) Nees & Metcalfe (= C. meyenianus Kunth
    Mariscus pennatiformis (Kukenth) T. Koyama & Metcalfe (= C. pennatiformis Kukenth)
    Toruliniuum odoratum auriculatum (Nees & Mayen ex Kunth) T. Koyama (= C. odoratus L.)

Species reported from Hawai‘i NOT included above:

    Cyperus confertus SW.
    Cyperus esculentus L.
    Cyperus flavescens L.
    Cyperus sphacelatus Rottb.
    Cyperus stoloniferus Retz.
    Cyperus trinervis R. Br.
    Cyperus virens Michx.
    8 species of Mariscus (= Cyperus)

Species reported from Guam NOT included above:

    Cyperus compactus Retz. (possibly not naturalized)
    Cyperus compressus L.
    Cyperus flavidus Retz.
    Cyperus tenuiculmis Boeck (?)

SEDGE (Cyperus) PHOTOS
[CLICK ON THUMBNAIL TO OPEN AN ENLARGED IMAGE]
C Trachysanthos spikelet

Fig. 32I. Portion of spike of C. trachysanthos showing glumes with recurved mucros (717 KB).

Table of Contents HAW TABLE OF CONTENTS  Table of Contents GUM TABLE OF CONTENTS  To grass inflorescence types INFLORESCENCE TYPES  AECOS AECOS, Inc.

© 2016-24 AECOS, Inc. [ver: 240419] To next page Page 32
bottom graphic