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[GENUS PASPALUM] |
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35a
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( 31) |
inflorescence only terminal on each stem (one per stem); inflorescence of one to many rachises (branches). Plant tufted (cespitose) OR spreading by either stolon or rhizome (rootstock) .. .
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[36]
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35b
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Inflorescences both terminal and axillary (multiple on the same stem; not the same as multiple branches on the same culm). Plant tufted (cespitose) .. .
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[58]
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36a
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(35) |
Plant cespitose, clump-forming .. .
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[43] |
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36b
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Plant spreading by stolons or rhizomes .. .
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[37] |
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~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~
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37a
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(35) |
Plant spreading by stolons (stems growing horizontally outward and rooting at nodes). Ligule an eciliate (lacking hairs) membrane .. .
Sorry, not the best couplet. Looking for a more difinitive division here.
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[38] |
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37b
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Plant spreading by underground "rootstock" (rhizomatous) although also may have culms rooting at nodes. Ligule either a membrane or row of stiff hairs.
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.. .
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[40] |
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38a
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(37) |
Racemes thin to 2.5 in (10 cm) long each, widely spreading, resembling an old TV "rabbit ears" antenna. Spikelets minute, under 0.1 in (2 mm) in length; upper glume with with short hairs around margin. { Common small, spreading grass found in the wild and a lawn grass mostly in wet, windward areas. Hilo grass, mau‘u Hilo. [HAW - NAT] [FAC] [GUM - NAT] Paspalum conjugatum Bergius
Be sure to confirm the disc-shape of the small spikelets, as many Digiteria present with just two racemes.
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38b
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Plants glabrous or not, infrequently flowering, inflorescence similar to above but racemes a little more robust, shorter. Stolons 1-3 mm in diam., nodes spaced more than 1 cm apart. Spikelets >0.1 in (>2 mm) long, tips acute, narrowly prolonged (and may be slightly curved) at apex; upper glume lacking hairs around margin. { Grasses typically (although not necessarily) aquatic, forming a dense, dark green growth along the margin of fresh or brackish aquatic environments.
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[39] |
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39a
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(38) |
Leaf blades stiff, somewhat distichous (leaves appear two-ranked) towards upper end. Culms and leaves without hairs except perhaps for a ring at the truncate, membranous ligule. Spikelets 3.0-4.5 mm long. { In the wild, seen mostly lining estuarine water bodies. Used as a lawn grass in areas of saline soil. Seashore paspalum [HAW - NAT] [FACW]
Somwhat resembles in habit (distichous leaf arrangement) and habitat, Sporobolus virginicus and Distichlis spicata.
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39b
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Leaf blades conspicuously alternate up the culm. Hawai‘i plants lacking conspicuous hairs (mosly glabrous), although spikelet pedicels with abundant short, curved hairs (requires magnification). Spikelets 2.4-3.2 mm long. Ligule prominant, a membrane rounded at upper margin. { Spreading perennial in wetlands and wet soils. Knotgrass [HAW - NAT] [FACW], saltgrass, knotgrass, couchgrass [GUM - IND] [FACW]
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40a
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(37) |
Panicle branches usually just 2, paired at upper end of inflorescence. Spikelets in single row on each side of rachis (packed in two rows) .. .
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[41] |
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40b
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Panicle branches on axis of inflorescence 3 or more, these arraged alternately up the axis. Spikelets paired on rachis (packed in four rows) .. .
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[42] |
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41a
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(40) |
Plant spreading by underground "rootstock" (rhizomatous). Inflorescences with 2 (rarely 3) racemes. Spikelet broadly elliptic, plump, 2.5-3.9 mm long, glabrous (without hairs); rachis broad, deep purple in color. Lower glume absent. Ligule a fringe of hairs { Small lawn grass. Bahia grass. [HAW - NAT] [UPL] [GUM - NAT]
Plant somewhat resembles Axonopus with smaller spikelets and ligule a low, cilolate membrane.
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41b
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Inflorescences with 2 (rarely 3) racemes. Spikelet 1.9 to 2.3 mm long, glabrous; { Small grass spreading by short rhizomes. [HAW - NAT]
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42a
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(40) |
Spikelets with apex obtuse. See also couplet [51] { [HAW - NAT]
Paspalum mandiocanum var. mandiocanum Trin.
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42b
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Leaf sheaths variable; glabrous on most plants, but strongly hirsute sheaths also seen. Ligule membranous. Inflorescence of 4-8 racemes. Spikelets acute-tipped, glabrous, each 2.8 mm long by 1.5 mm wide; lower glume absent. { Plants strongly stoloniferous. [HAW - NAT]
Paspalum jesuiticum Parodi
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43a
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(36) |
Inflorescence of fewer than 10 racemes .. .
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[44] |
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43b
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Inflorescence of more than 10 racemes (occasionally less if recently mowed) .. .
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[52] |
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[NOTE: THREE CHOICES HERE]
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44a
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(43) |
Spikelets fringed with a broad, ragged or lacerate (much cut) margin. Leaves broad, distinctly wavy; ligule a fringe of hairs. { Medium size, annual, clumping grass in mesic to wet areas; often a weed in lawns. Panama grass, fimbriate paspalum. [HAW - NAT] [FAC] [GUM - NAT]Paspalum fimbriatum Kunth
Figure 6D. Close-up of spikelets of Panama grass with lacerate wing of 1st lemma of one spikelet outlined in black. Note also, prominent midnerve prolonged beyond apex of each lemma (bract).
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44b
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Spikelets fringed with hairs (ciliate or pubescent; may be very small); lacking a surrounding ragged wing. Leaves, if broad, not wavy; ligule an eciliate membrane .. .
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[45]
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44c
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Spikelets without fringing hairs (glabrous) .. .
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[48]
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45a
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(44) |
Spikelets 2.5–2.8 mm long; upper glume fringed with stiff, spreading hairs. { [HAW-NAT]
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45b
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Spikelets 1.8–4.5 mm long; Upper glume fringed with soft hairs .. .
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[46]
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46a
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(45) |
Hairs on florets minute; usually not visible without magnification. See also couplet [57] { [HAW-NAT] [FACW]
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46b
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Hairs on florets long and wispy (at least some 1 mm long, visible
without magnification) .. .
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[47]
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47a
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(46) |
Racemes typically 3 to 7, widely spreading. Spikelets measure more than 0.1 in (2.5 - 4.5 mm) in length. { Medium size, fairly common grass in wet to dry areas, sometimes a coarse weed in lawns. Dallis grass [HAW - NAT] [FACU] [GUM - NAT]
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47b
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Racemes usually more than 10, loosely appressed to the rachis. Spikelets measure less than 0.1 in (2 - 2.8 mm) in length, typically with a purplish caste. Ligule a dense cluster of long, stiff hairs. See also couplet [57] { Medium size, coarse grass in wet areas, sometimes in or near flowing streams. Vasey grass [HAW - NAT] [FAC] [GUM - NAT]
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48a
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(44) |
Spikelets in pairs on each side of rachis midrib, borne on short pedicels (one slightly longer than the other), forming four rows of spikelets (NOTE: if only two rows, then pedicel evident indicating missing spikelet of each pair or rows very untidy).
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[49] |
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48b
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Racemes widely spaced, 4 to 6 on culm, some bent downward (deflexed). Leaf blades narrow, under 1/2 inch (12 mm) across, mostly without hairs (glabrous). Ligule a low membrane. Only one spikelet present on each side of midrib, forming two, closely imbricate rows of spikelets (rarely a few spikelets paired). Spikelets glabrous, broadly elliptic in outline, greater than 1/16 in (2.0-2.5 mm) in length; { Perennial, tufted medium-size grass growing on thin, poor soils or in wetland soils. USDA noxious weed. Ricegrass, ditch millet, mau‘u laiki [HAW - ?IND] [FAC], kodo [GUM - IND] Paspalum scrobiculatum L.
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49a
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(48) |
Lower glume absent .. .
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[50] |
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49b
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Raceme 1 or 2 (rarely up to 4) on each culm, rachis without scattered hairs; spikelets 2.2-2.6 mm long, minutely pubesent (at least upper glume). Lower glumes present, but lower glume of upper spikelet of pair notably the larger. See also couplet [59] { Annual or perennial [HAW NAT] Paspalum langei (E. Fourn.) Nash
NOTE: unclear whether P. longifolium—now a synonym of P. sumtrense Roth and listed by Clayton &. Snow (2010) as present in the Hawaiian and Marianas Islands—occurs there. Faccenda (2022) found no correct identification of this species for Hawai‘i. If present, this species would probably key out here, differing in having stiff erect, folded leaves and (usually) more than 4 racemes, these with stiff hairs at the junction with the rachis.
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50a
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(49) |
Leaves linear, their width uniform or tapering from base; fertile
lemma dark glossy brown; leaves less than 9 mm (1/3 in) wide. See also couplet [53]. { [HAW-NAT] Paspalum plicatulum Michx.
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50b
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Leaves lanceolate, their width greatest above the base, at least some leaves >10 mm (0.4 in) across. Fertile lemma
pale .. .
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[51] |
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51a
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(50) |
Leaf blades mostly over 1 ft (30 cm) long and up to 1 in (2.5 cm) wide; margins ciliate (having long hairs). Ligule a tall membrane. Culms 2-6 ft (70-200 cm) long; racemes typically 5 to 10(-15). Spikelets puberulent or woolly on margins, nearly 1/8 in (2 to 2.7 mm) in length; floret yellow. { Perennial, medium size, coarse grass forming substantial tufts in open field in mesic locations. [HAW - NAT] Paspalum macrophyllum Kunth
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51b
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Leaves appressed pilose; margins scabrous or smooth, without cilia. Spikelets glabrous or with a few hairs on edge of glume. See also couplet [42]. { [HAW][NAT] Paspalum mandiocanum Trin.
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52a
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(43) |
Spikelets with a noticeable bulge in central portion and about 1 mm thick OR thinner but hemispherical .. .
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[53] |
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52b
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Spikelets uniformly compressed, about 0.5 mm thick .. .
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[54] |
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53a
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(52) |
Leaves linear, their width uniform or tapering from base; leaves < 9 mm wide. Spikelets ~1 mm thick, with central bulge; fertile lemma dark glossy brown. See also couplet [50] { [HAW][NAT]Paspalum plicatulum Michx.
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53b
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Leaf collar with long white hairs. Racemes very numerous, ten to as many as 60, these purplish to brownish tinged and crowded on the axis. Spikelets about 1/16 in (1.0-1.4 mm) in length, suborbicular, pubescent, plump (hemispherical); floret pale; seed dark. See also couplet [56]. { Perennial, medium size, coarse grass in wet areas. Very common across Guam. No common name in Hawai‘i [HAW - NAT] [UPL] or Guam [GUM - NAT] [FAC] |
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54a
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(52) |
Spikelets entirely without hairs (glabrous) .. .
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[55] |
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54b
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Spikelets with at least some hairs .. .
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[56] |
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55a
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(54) |
Sterile lemma ribbed over veins; both glumes lacking. { weak grass with culms typically < 6 mm diameter at base. [HAW]{NAT] Paspalum malacophyllum Trin.
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55b
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Sterile lemma smooth; upper glume present; robust grasses with culms ~1 cm diam. at base. { Typically found in disturbed wetlands. [HAW][NAT] Paspalum arundinaceum Poir.
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56a
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(54) |
Leaf collar with long white hairs. Racemes very numerous, ten to as many as 60, these purplish to brownish tinged and crowded on the axis. Spikelets about 1/16 in (1.0-1.4 mm) in length, suborbicular, evenly pubescent, plump (hemispherical); floret pale; seed dark. See also couplet [53]. { Perennial, medium size, coarse grass in wet areas. Very common across Guam. No common name in Hawai‘i [HAW - NAT] [UPL] or Guam [GUM - NAT] [FAC] |
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56b
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Spikelets with hairs concentrated on glume edge; spikelets 2–3 mm long .. .
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[57] |
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57a
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(56) |
Glume with a long-ciliate fringe around the edge. See also couplet [47] { [HAW - NAT] [FAC] [GUM - NAT] |
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57b
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Glume with a short-ciliate fringe around the edge. See also couplet [46] { [HAW - NAT] [FACW] |
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58a
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(35) |
Spikelets paired on the rachis (two spikelets on each side, one on a slightly longer pedicel); spikelets with lower glumes present .. .
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[59] |
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58b
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Spikelets not paired, only one on each side of rachis midrib; lower glumes absent .. .
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[60] |
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59a
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(57) |
Raceme a single branch on each culm, rachis usually with scattered hairs. Spikelets 2.6-3.2 mm long, glabrous; Lower glume of lower spikelet larger than lower glume of upper spikelet. { Perennial [HAW NAT]
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59b
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Raceme 1 or 2 (rarely up to 4) on each culm, rachis without scattered hairs; spikelets 2.2-2.6 mm long, minutely pubesent (at least upper glume). Lower glumes present, but lower glume of upper spikelet of pair notably the larger. See also couplet [49]. { Annual or perennial [HAW NAT]Paspalum langei (E. Fourn.) Nash
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60a
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(58) |
Racemes typically 1 or 2(-5). Spikelets glabrous on margins, less than 1/8 in (1.4 to 2.6 mm) in length. Leaf blades mostly well under 1 ft (30 cm) in length, up to 3/4 inch (2 cm) wide; culms 1-3 ft (30-90 cm) long. Ligule a short membrane. { Perennial, medium size grass found on Midway and Guam. [HAW - NAT] [FACU] [GUM - NAT]
Somewhat resembles closely related but smaller Axonopus spp. with less compressed and narrower spikelets acute at apex
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59b
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Not as above .. .
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[100] |
Grass plants attributable to the genus Paspalum are usually easy to spot in the field, most having spikelets of a distinct shape (Figure 6A). The inflorescence of a Paspalum (Figure 6B, below) comprises two or more (one in a couple of species) racemes (branches) attached along an axis (cuilm) rising well above the uppermost leaf blade. Spikelets are attached by short pedicels (stalks), arranged either singly or paired, in two rows along one side (the abaxial face: facing outward or downward) of the flattened rachis. The broadly elliptic to disk-shaped (plano-convex) spikelets are distinctive to Paspalum. Note also the prominent single mid-vein (Fig. 6A).
Twenty-two species of Paspalum are reported to be present in Hawai‘i (Clayton & Snow, 2010; Faccenda, 2023a) and many are common in mesic to wet environments, including wetlands. Raulerson (2006) lists thirteeen species from Guam. All Paspalum species in Hawai‘i are naturalized species (non-native), except P. scrobiculatum (mau‘u laiki)—a southeast Asian species distributed across the Pacific Islands—is possibly indigenous or a very early Polynesian introduction. Five species of Paspalum on Guam may be native to the Marianas. This key recently expanded based on work published by Faccenda (2023a).
