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CPIE Notebook Project - Grasses of Hawai‘i and Guam Grass Key – Page 2
Canes and Very Large Grasses

In terms of size or height specifically, most grasses range from small (such as grasses in a park lawn) to large and reaching or perhaps a little exceeding a human in height (see definitions on Page iv). Some grasses are much larger, close to 10 feet (large grass) or, in the case of some bamboos, exceeding 70 feet (very large grass). Cenchrus purpureus on Guam is reported by Stone (1970) to have culms reaching over 20 ft. However, some of these grasses may start out modest in size and take years to pass from modest to very large. Some may never reach their potential, depending upon growing conditions. A familiar example is corn, a large grass. However, corn in the backyard garden may never tower over it's gardener, even while producing perfectly delicious fruit. The grasses on this page are typically at the upper end of "large" to "very large", but their gestalt may be in the coarseness of their features as much as in their height.
[CANES AND LARGE GRASSES]      
[NOTE THREE CHOICES HERE]      
15a (To last page11) Grass large to very large, clumping and without visible stems (not counting flowering culm); OR leaves emitting a distinct citrus-like smell upon crushing .. . [16]
15b

Grass large to very large, clumping or spreading but with leaves arranged along a vertical stem, culm nodes covered by leaf sheaths { a reed or cane; or forming dense, nearly impenetrable, clumps .. .

[18]
15c Grass moderately large to very large, but with woody culms and the culm nodes conspicuously exposed. Leaf blades generally short, not linear (except in ornamental weeping bamboo). Bamboos. ~ Subfamily BAMBUSOIDEAE .. . [24]
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16a (15) Leaves distinctly aromatic with an odor of citrus. Inflorescence rarely produced in Hawai‘i. { Grass a tuft 4 feet (1.2 m) high or less .. . [26]
16b

Leaves NOT strongly or at all aromatic. Inflorescence a showy white to purple plume up to 3 feet in length { Grass a tuft to 10 feet (3 cm) high, with long, arching, sharp-edged leaves .. .

[17]
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17a (16) Leaves and culm with an abundance of hairs on sheaths. { An HDA noxious weed. Pampas grass [HAW - NAT] [FACU]
    Cortaderia jubata (Carriere) Stapf
17b Leaf and culm sheaths glabrous on outside surfaces. { Nurseries offer yellowish, stark white, and pink varieties, sold as seed; however, this grass is an HDA noxious weed and should not be planted as an ornamental in Hawai‘i or Guam. Pampas grass [HAW - NAT] [FACU]
    Cortaderia selloana (J.A. & J.H. Schultes) Ascherson & Graebner
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18a (15) Culms reed or cane-like, stiff but not woody. Younger leaf blades relatively broad (length may be less than 10x width), but older blades linear .. .
[19]
18b



 photo of Miscanthus twice height of biologist standfing beside it.

Plant not a cane, but of typical grass form. Leaf blades relatively broad but definitely linear (length exceeds 20x width). { Forming tall, dense clumps (Fig. 2A) .. .

Figure 2A. Sword grass (Miscanthus floridulus), a common, very large grass growing on volcanic soils of southern Guam.
[24]
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19a (18) Stems much branched .. . [23]
19b

Cane-like stems usually unbranched; if clumping and multiple stemmed, the stems are suckers growing up from base .. .

[20]
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20a (19) Annual or perennial, reedlike herb with a solid (not hollow)stem .. . [21]
20b

Arundo donaxPerennial reed with hollow stem, usually unbranched. Leaf margins wavy only at base of blades if at all; blades to 2.4 inches across. Inflorescence an erect oblong panicle with complete florets (both sexes present) (Fig. 2B). Giant reed, Spanish reed [HAW ORN] [FAC] [GUM - NAT]

    Arundo donax L.

Figure 2B. Small Arundo donax in
abandoned garden in Wai‘anae.
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21a (20)
Corn plants at farm
Figure 2C. Zea mays in cultivation—short seed crop variety.
Annual herb. Leaves with wavy margins and up to 5 inches across, the sheaths overlapping. Male and female flowers on separate inflorescences: male spikelets on a terminal panicle; female spikelets on spikes produced in the leaf axils, producing long pistils (silk) and edible fruit. Corn, maize, kūlina [HAW - ORN], mais [GUM - ORN]
    Zea mays L.
21b

Perennial herb. Leaves stiff, margins not wavy and under 2 in across. Inflorescence a large, terminal plume, inflorescnce not as above: spikelets all alike and paired on the rachis. Genus Saccharum .. .

[22]
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[NOTE THREE CHOICES HERE]
22a (21) Plant clump forming; cane green, red, or yellow in color. Peduncle glabrous (pilose in some hybrid cultivars). Leaf blades to 2.5 inches wide; sheaths overlapping. Blades mostly glabrous, but with tufts of long hairs at collar. Ligule a membrane topped with short hairs and a row of stiff hairs behind ligule. { At one time intensively cultivated on most of the Hawaiian Islands, but not so on Guam. Sugar cane, kō [HAW - ORN, POL] [FAC], tupo or tupu [GUM - ORN, ABO].
    Saccharum officinarum L. or a hybrid/cultigen

Numerous varieties have been grown in Hawai‘i since ancient times (see Lincoln, 2017).

22b Plant speading by rhizomes. Cane green in color. Peduncle hairy below the panicle; rachis fragile. Leaf blades 0.2 to 0.8 cm (<1 in) across. { Very abundant and widespread grass across much of Guam; resembles sugar cane but generally more slender. USDA noxious weed. Wild cane [HAW - NAT] [FAC] [GUM - NAT] [FACU]
    Saccharum spontaneum L.

On Guam, consider similar-appearing sword grass (Miscanthus floridulus).

22c Plant clump forming; cane red in color, Peduncle hairy below the panicle. Leaf blades 1-6 cm (0.4 to 2.4 in) wide. { An early sugar cane hybrid of limited distribution in Hawai‘i: found along road leading to ‘Akaka Falls State Park on Hawai‘i Island (Faccenda, 2023a). [HAW - NAT]
    Saccharum x sinense Roxb.
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23a (19) Leaves deep green, typically broad and wavy. Inflorescences numerous at top and from axils and unusual in having "seed-like" white to gray cupule structures supporting pistillate and staminate racemes. { a robust annual growing to nearly 10 ft in and along the margins of streams and other wet areas. Job's tears, pū‘ohe‘ohe [HAW - NAT] [FACW] [GUM - NAT] [FACW]
    Coix lachryma-jobi L.
23b Leaves deep purple to reddish bronze. Inflorescence a purplish foxtail. { Smaller clumps look like fountain grass but larger plants (to 10 feet) are cane-like. Burgandy fountain grass (see also couplet [58]). [HAW - ORN]
    Cenchrus elegans (Hassk.) Veldk.
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24a (18) Inflorescence a long, yellow foxtail. Leaves with prominent, white midrib, glabrous (not hairy) or with long hairs at margins near collar; ligule a thin membrane topped with tight packed hairs. { Grass forming impenetrable, close-set clumps in mesic to wet areas, particularly near streams. Elephant grass, Napier grass. [HAW - NAT] [FAC] [GUM - NAT]
    Cenchrus purpureus (Schumach.) Marrone
24b Infloresence an open panicle .. . [25]
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25a (24) Culms up to 3 m (10 ft) long bearing a panicle some 50 cm (1.5 ft) long (Fig. 2A). Spikelets paired on racemes (one sessile, one pedunculate). Ligule a truncate membrane. { Grass forming impenetrable, close-set clumps (see Fig. 2A, above) in (mostly) volcanic soils of southern Guam. Leaf margins armed with tiny, very sharp teeth that easily slash flesh. HDA noxious weed. Sword grass, neti. [GUM - IND] [FACU]
    Miscanthus floridulus (Labill.) Warburg ex Schum. & Lauterb.
On Guam, consider similar-appearing wild cane (Saccahrum spontaneum).

25b Culms typically under 2 m, in many cases much smaller. Leaf blades on mature plants up to 1 in (3 cm) across. { An extremely common, clumping grass in lowland disturbed areas and abandoned pastures in mesic and wet areas. Stems have stiff hairs that cause itching as hairs detach and irritate the skin. Guinea grass [HAW - NAT] [FAC] [GUM - NAT] [FACU]
    Megathyrsus maximus (Jacq.) B.K. Simon & W.L. Jacobs
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26a (16) Leaves lemon-scented. Base of "stem" greenish in color. Inflorescence rarely produced in Hawai‘i. { Grass used in cooking to impart a lemon scent. Lemon grass [HAW - ORN] [GUM - ORN]
    Cymbopogon citratus (C. Nees) Stapf
26b Leaves citronella scented. Base of "stem" reddish in color. { Source of citronella oil, planted to repel insects such as mosquitos. Citronella grass [GUM - ORN]
    Cymbopogon nardus (L.) Rendle

Synonyms for grasses on this page:

    Panicum maximum Jacq. (= Megathyrsus maximus)
    Pennisetum macrostachyum (Brong.) Trinius (= Cenchrus caninus)
    P. purpureum Schumach.(= Cenchrus purpureus)
    Urochloa maxima (Jacq.) Webster (= Megathyrsus maximus)
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