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CPIE Notebook Project - Common Hawaiian Grasses Page 20

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Common Lawn Grasses

This subkey to lawn grasses provides an opportunity for the interested naturalist to learn a limited number of grasses exploring readily accessed habitats like park and neighborhood lawns. Lawns represent a relatively consistent environment for a suitable grass species, so growth charactereristics are less variable and more recognizable than in the wild. Although idenifying a grass requires examining the inflorescence, once a particular lawn grass is identified, it usually can be recognized when not in flower. Most lawn grasses flower continuously, but mowing and seasonal limitations of some may result in inflorescences being unavailable, at least temporarily.

Lawn grasses are both perennial (plant lives more than two years) and creeping in habit, spreading outward by either rhizomes or stolons or both. These abilitiess allow them to build a turf, a highly desirable quality for a lawn. Clumping grasses make very poor lawn grasses because they grow mostly upwards and not outwards, making them susceptible to killing by mowing. Typically, a clumping grass that invades a lawn would be regarded as a weed. However, some small clumping grasses found in lawns are included in this subkey.

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30a (9) Leaf blades extremely thin, 1/16 inch (1 mm) across or less, needle-like if stiff, thread-like if arching [31]
30b

Leaf blade not as above, typically at least 1/8 inch (3 mm) across at widest point

[35]
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31a (30) McCoy grass flowering head Leaf blades filiform (thin, thread-like, 1 mm wide or less) and arching, no more than 6 or 7 inches (15 cm) long, typically somewhat less, 3 or 4 arising at the base of a somewhat lax flowering culm. Flower head at tip of culm a cluster of 2 to 6 flattened spikelets and two or more long, filiform bracts. { growing in moist, shaded areas of a lawn, spreading by plantlets. McCoy grass, mau‘u hunehune. [NAT]
Family CYPERACEAE (a sedge) —
Cyperus gracilis R. Br.
31b

Leaf blades thin, but generally rather short and stiff. Flower head without filiform bracts. Fine-textured sod-forming lawn grass

[32]
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32a (31) Inflorescence (flower head) a single, short spike. { Sod tight but tending to hump up. Zoysia grass. (33)
32b

Infloresence of multiple spikes (3 to 6, typically 4) radiating out from top of culm. { Sod flat, not tending to form humps. Bermuda grass.

(34)
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33a (32) & (51) Blades very narrow (0.04 in or 1 mm) and flowering heads about 1/2 in (1.5 mm) long, barely projecting above leaf blades. Mascarene grass, velvet grass, ma‘u kepani. [NAT]
Zoysia matrella var. pacifica Goudswaard
<A>
33b

Blades wider (0.06-0.09 in or 1.5-2.3 mm) and flowering heads to 1.75 in (4.4 cm) long, projecting well above leaf blades. Manila grass [NAT]

Zoysia matrella var. matrella Merr.
<A>
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34a (32) Blades usually 2 in (5 cm) long or more and 0.1-0.15 in (2.5-4 mm) wide. Bermuda grass, mānienie. [NAT]
Cynodon dactylon (L.) Pers.
34b

Blades 1.75 in (mm) long or less and very narrow (0.08 in or 2 mm wide). Hybrid Bermuda; various cultivars (e.g., 'Tifdwarf'). [ORN]

Cynodon x magennisii Hurcomb
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Kikuyu grass lawn

Figure 20C. A lawn of Kikuyu grass with anthers on white filaments extending an inch or so above the mowed surface (Waimea, Hawai‘i). Click here to download a close-up image showing the stigmas: Fig. 4E. Kikuyu grass with stigmas.
35a (30) Grass appearing not to ever flower, but on close examination, the spikelets are seen to be enclosed in the uppermost leaf sheath, so only filaments and/or stigmas are normally exposed (see Fig. 20C above). { forms a thick turf from runners and stolens, typically at higher elevations such as in Waimea on the Big Island and upcountry Maui. Kikuyu grass. [NAT]

Cenchrus clandestinus (Hochst. ex Choiv.) Morrone
35b

Grass produces flowering heads on culms that rise above at least the base of the blade

[36]
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36a (35) Flowering head (inflorescence) consists of one to many spikes or racemes attaching laterally (if more than one) or terminally (if one) to the culm [37]
36b

Flowering head an open panicle: spikelets attached by short or long stalks (pedicels) to a branching culm

[40]
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37a (36) Inflorescence a single spike, unbranched, rising above the turf or extending out from near the leading edge of stolons

[38]
37b Racemes or spikes two or more on a culm

[39]
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38a (37) Inflorescence of St. Augustine grass

Inflorescence a thick, single spike-like axis, 1 to 3 in (3-8 cm) long with spikelets inserted in grooves. Stems thick. Leaves usually grey-green, blunt-tipped, and folded. { Extensively running grass used widely in lawns in drier areas, especially in sandy soils, forming a thick, spongy turf under good conditions. St. Augustine grass, buffalo grass, ‘aki‘aki haole. [NAT]

Stenotaphrum secundatum (Walter) Kuntze

Figure 20D. Inflorescence of St. Augustine grass. This grass flowers infrequently. Short grey (called blue), folded leaves with rounded tips, coarse creeping stems, and spongy mat can be helpful identifying characteristics in the absence of a flower head.

38b Rachis of inflorescence not thickened to prominence over spikelets, rather more typically narrow and partly hidden by spikelets. Spikelets not in grooves, but arrayed in one side of rachis. Grass not coarse. { Extensively running by stolons forming a thick, shallow-rooted sod in nearly full sun. Centipede grass, Honan grass. [ORN]

Eremochloa ophiuroides (Munro) Hack.
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39a (37) Racemes or spikes two or more, all (or all but an uppermost pair) spaced out along the culm

[40]
39b Racemes or spikes more than two and arising from a common point or very close together at the top of the culm: an arrangement called digitate

[80]
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40a (39) Racemes nearly always two in number (rarely three), these widely spreading, resembing an old TV "rabbit ear" antenna [41]
40b

Racemes nearly always three or more per culm

[42]
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41a (40) Magnifying Lens Tiny spikelets ovate, only slightly longer than wide. Racemes nearly always two (very rarely three). { Popular lawn grass in wet, windward areas. Hilo grass, mau‘u Hilo. [NAT]
Paspalum conjugatum Bergius
41b

Spikelets elongate, much longer than wide. Racemes usually three in number, one typically shorter, but often only two present. { A delicate, typically lanky, small grass appearing as a weed in lawns. [NAT]

Digiteria radicosa (J. Presl.) Miq.
41c

Grass not exactly as above. Racemes typically more than three in number. Spikelets elongate, but plant either spreading by stolons or, if clumping, then not particularly delicate. Several other species of Digitaria may appear as weeds in lawns; none is a "lawn" grass. Genus Digitaria

[35]
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42a (40) [39]
42b

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NOTE A
    Hybrids of the two varieties of Zoysia grass (e.g., 'Emerald') and between Z. matrella and other Zoysia species (e.g., 'El Toro', 'Z-3', 'Z-52') are available as stolons, plugs, or sod and widely used (e.g., golf course greens).

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