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CPIE Notebook Project - Common Hawaiian Grasses Page 19


Key to Genus Eragrostis Wolf

Grasses of the genus, Eragrostis (commonly called lovegrasses), are small to medium clumping grasses that are relatively easy to recognize in the field if you closely examine the spikelets. Each spikelet typically comprises several to many florets, the latter arranged in a flattened, oval or much elongated "oval" (linear) with the florets tightly imbricate (packed close together, alternating along the rachis; think articulated fish charm). At the base of each spikelet are two, more or less similar, glumes. Each spikelet is attached to a thin pedicel. Species of Poa, Bromus, and a few other genera might be confused with Eragrostis spp., having a somewhat similar arrangement of the florets.

Twentyfour (24) or 25 species of Eragrostis are reported to be present in Hawai‘i (Clayton & Snow, 2010; Imada, 2012); most are not commonly encountered. Ten (10) of the Eragrostis species here are native and all but one, endemic (unique to Hawai‘). Thus, this genus is an important component of the native flora. However, the two most common species in disturbed lowland sites are non-natives: Carolina lovegrass (E. pectinacea, extremely ubiquitous) and Japanese lovegrass (E. amabilis).

panicle of sheepgrass spikelets

Figure 17A. The inflorescence of sheepgrass
 (Eragrostis brownei), here showing nine spikelets typical in form of most Eragrostis species. Note spreading, subequal glumes at base of each spikelet; the glumes are shorter than the first lemma (floret).

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90a (88) Inflorescence open, the branches spreading [91]
90b

Inflorescence narrow, spike-like, branches pressed against the culm or at least ascending and contracted, almost forming a column of densely-packed spikelets

[98]
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91a (90) Spikelets very small, less than 1/8 in (3 mm) across and 1/3 in (0.8 cm) long [92]
91b

Individual spikelets larger, at least 1/8 in (3 mm) across and 1/4 in (1 cm) long

[93]
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92a (91) Spikelets 4 to 6 flowered, slightly longer than wide (~1/16 in or 2 mm long). Small grass of dry areas and disturbed sites. Japanese lovegrass. [NAT]

Eragrostis amabilis (L.) Wight & Arnott
92b

Spikelets 5 to 18 flowered, at least twice as long as wide (1/8 to 1/3 in (3 to 8 mm)) long. Small grass of moist to wet, disturbed sites. Carolina lovegrass. [NAT]

Eragrostis pectinacea (Michx.) Nees
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93a (91) Some or all mature spikelets with more than 30 florets, linear in shape. Medium grasses, culms usually erect [95]
93b

Mature spikelets all with fewer than 30 florets, typically 10 to 15 more or less, oval or elongated oval in shape. Usually small grasses, culms typically prostrate or decumbant, sometimes erect

[94]
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94a (93) Magnifying Lens Glumes aristate: having a small prolonged tip or short awn. Sheepgrass. (Fig. 17A) [NAT]
Eragrostis brownei (Kunth) Nees ex Steud.
94b

Glumes obtuse or acuminate (coming to a sharp-angled tip), but not aristate

[95]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
98a (90) Spikelets hairy, margins of lemmas fringed with long cilia, keels scabrous; glumes lacking hairs, although keels scabrous with curved "hairs". Glumes subequal, shorter than first lemma. Spikelets 3-4 mm long. {Small, annual, clumping grass in dry areas. [NAT]
? Eragrostis ciliaris (L.) R. Br. Kunth

98b

Spikelets not as above, not fringed with hairs.

[99]
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Species of Eragrostis reported to be in Hawai‘i
  but not covered in this key; and some synonyms:

    E. atropioides Hillebr.
    E. cilianensis (All.) Link
    E. ciliaris (L.) R. Br.
    E. deflexa Hitchc.
    E. fosbergii Whitney
    E. grandis Hillebr.
    E. leptophylla Hitchc.
    E. leptostachya (R. Br.) Steud. (syn.: E. hosakai Degener)
    E. mauiensis Hitchc.
    E. monticola (Gaud.) Hillebr.
    E. paupera Jedwabn.
    E. tenella (L.) P. Beauv. (= E. amabilis)
    E. variabilis (Guad.) Steud.

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