17.19   LEPTOCHLOA P. Beauv.
Neil Snow

Plants annual or perennial; cespitose. Culms (3)10-250(300) cm, usually ascending to erect, often geniculate at the lower nodes, occasionally prostrate and rooting at the lower nodes, often branching at the aerial nodes; nodes usually glabrous; internodes usually hollow. Leaves usually primarily cauline, occasionally in basal rosettes; sheaths open; ligules 0.2-10(15) mm, obtuse to attenuate, usually membranous, sometimes ciliate; blades flat, involute when dry, usually ascending to erect, apices attenuate. Primary inflorescences terminal, panicles of 2-150 non-disarticulating, spikelike branches, usually exceeding the leaves; branches 1-22 cm, digitate, subdigitate, or racemose on the rachises, 1-sided, usually spikelet-bearing throughout their length, spikelets in 2 rows, axes terminating in a functional spikelet, lower branches occasionally with secondary branching; secondary panicles sometimes present, axillary to and concealed by the lower sheaths, their florets not disarticulating; disarticulation in the primary panicles beneath the florets. Spikelets rounded to slightly keeled on the back, distant to tightly imbricate, not conspicuously pubescent, with (2)3-12(20) bisexual florets; rachillas rarely prolonged. Glumes usually unequal, sometimes subequal, exceeded by the florets, membranous, rounded to weakly keeled, 1-veined, veins scabrous, apices unawned (rarely mucronate); lower glumes 0.5-4.9 mm; upper glumes 0.9-6 mm; florets usually bisexual; calluses distinct or poorly developed, glabrous or pubescent; lemmas membranous, usually pubescent at least over the lower portion of the veins, 3(5)-veined, apices entire or minutely bilobed, unawned, mucronate, or awned; paleas usually subequal to the lemmas, membranous or hyaline; anthers 1-3, 0.1-2.7 mm. Caryopses obovate to elliptic, falling free of the lemmas and paleas. x = 10. Name from the Greek leptos, slender, in reference to the panicle branches, and chloa, grass.

Leptochloa is a pantropical, warm-temperate genus of 32 species. Eight of the ten species in this treatment are native to the Flora region. Of the other two, L. chloridiformis was introduced over 60 years ago but has not become established. Leptochloa chinensis is not yet known from the region; it is included here because of its potential threat as an invasive weed. Cladistic studies (Snow 1997) do not support recognition of the segregate genus Diplachne.

Leptochloa tends to grow in somewhat basic soils. Many of the species, particularly the annual species, are poor ecological competitors and grow in relatively open, seasonally inundated soils, such as are found along rivers. In disturbed areas, they are associated with roadside ditches, the margins of reservoirs, and mesic agricultural lands. A few species, primarily perennial, grow on well-drained soils. The vegetative vigor of all species is greatly influenced by soil moisture availability.

SELECTED REFERENCES Nicora, E.G. 1995. Los géneros Diplachne y Leptochloa (Gramineae, Eragrosteae) de la Argentina y países limítrofes. Darwiniana 33:233-256; Snow, N. 1997. Phylogeny and systematics of Leptochloa P. Beauv. sensu lato (Poaceae, Chloridoideae). Ph.D. dissertation, Washington University, St. Louis, Missouri, U.S.A. 506 pp.; Snow, N. 1998. Nomenclatural changes in Leptochloa P. Beauvois sensu lato (Poaceae, Chloridoideae). Novon 8:77-80.
Panicle branches digitate or subdigitate; plants perennial (2)
Panicle branches racemose; plants annual or perennial (4)
Lemma apices obtuse to truncate and often emarginate; lemmas membranous; plants often with secondary panicles concealed in the lower leaf sheaths ..... 1. L. dubia
Lemma apices usually acute; lemmas chartaceous; plants without secondary panicles concealed in the lower leaf sheaths (3)
Panicle branches always digitate, 7-17 cm long; lemmas mucronate but not awned; in the Flora region, known only from a few old collections in Cameron County, Texas ..... 2. L. chloridiformis
Panicle branches subdigitate, 1.5-18 cm long; lemmas unawned, mucronate, or awned; native in much of the southeastern United States, including parts of Texas ..... 3. L. virgata
Ligules 2-8 mm long, attenuate, becoming lacerate at maturity ..... 4. L. fusca
Ligules 0.3-5.4 mm long, truncate to obtuse, erose, ciliate, or lacerate (5)
Sheaths sparsely to densely hairy, the hairs papillose-based ..... 5. L. panicea
Sheaths lacking hairs or with hairs that are not papillose-based (6)
Panicles with 25-150 branches (7)
Panicles with 2-25 branches (10)
Lemmas 2.4-3 mm long; anthers 0.6-0.8 mm long; spikelets 4-5 mm long ..... 10. L. panicoides
Lemmas 1.2-2.4 mm long; anthers 0.2-0.6 mm long; spikelets 2.5-4.5 mm long (8)
Leaf blades 8-16 mm wide;lemmas 2.1-2.4 mm long ..... 7. L. scabra
Leaf blades 4-8 mm wide; lemmas 1-2 mm long (9)
Lower glumes 0.7-0.8 mm long; anthers 0.2-0.4 mm long; plants native to the southern United States ..... 6. L. nealleyi
Lower glumes 1.1-1.7 mm long; anthers 0.4-0.6 mm long; plants aggressive weeds, currently not known from the Flora region ..... 8. L. chinensis
Plants perennial (11)
Plants annual (12)
Lemmas 4-5 mm long, membranous, their apices broadly acute, obtuse, or truncate, unawned; panicles with 2-15 branches; caryopses 1.9-2.3 mm long, strongly dorsally compressed; secondary panicles often present in, and concealed by, the lower leaf sheaths ..... 1. L. dubia
Lemmas 1.5-3.6 mm long, chartaceous, their apices usually acute, rarely obtuse, unawned, mucronate, or awned, the awns to 11 mm long; panicles with 9-25 branches; caryopses 1.3-1.8 mm long, somewhat laterally compressed; secondary panicles not present in the lower leaf sheaths ..... 3. L. virgata
Panicles 2-17 cm long, with 5-23 branches; anthers 0.4-0.5 mm long; caryopses 0.4-0.5 mm wide ..... 9. L. viscida
Panicles 20-35 cm long, with 20-90 branches; anthers 0.6-0.8 mm long; caryopses about 0.7 mm wide ..... 10. L. panicoides

1.   Leptochloa dubia (Kunth) Nees
Green Sprangletop

Plants perennial. Culms (10)30-110 cm, round or basally compressed, tillering from the basal nodes, not branching from the aerial nodes, mostly glabrous, sometimes pilose basally; internodes solid. Sheaths sometimes with a pilose collar; ligules 1-2 mm, truncate, erose; blades (2)8-35 cm long, 2-8 mm wide, glabrous, strigose, or pilose. Panicles 8-20 cm, with 2-15 subdigitate or racemose branches; secondary panicles often hidden in the lowest leaf sheaths; branches 2-19 cm, ascending to spreading at maturity. Spikelets 4-12 mm, light brown to dark olive green, with 4-13 florets, often widely divergent at anthesis. Glumes narrowly triangular to ovate, acute; lower glumes 2.3-4.8 mm; upper glumes 3.3-6 mm; lemmas 3.5-5 mm, membranous, ovate to obovate, lateral veins glabrous or sericeous, hairs often restricted to the basal portion, sometimes also sericeous on the midvein and between the veins, apices obtuse to truncate, usually emarginate, unawned, sometimes mucronate; paleas ciliate on the margins; anthers 3, 0.3-1.6 mm. Caryopses 1.5-2.3 mm long, 0.9-1 mm wide, strongly dorsally compressed. 2n = 40, 60, 80.

Leptochloa dubia grows from the southwestern United States and Florida through Mexico to Argentina, often in well-drained, sandy or rocky soils. It provides fair to good forage, but is seldom abundant.

2.   Leptochloa chloridiformis (Hack.) Parodi
Argentine Sprangletop

Plants perennial. Culms 60-200 cm, erect, compressed, unbranched; internodes hollow. Sheaths pubescent; ligules 0.5-1 mm, shortly ciliate; blades 25-50 cm long, 2.8-5.5 mm wide, ascending to reflexed, adaxial surfaces usually sparsely pilose behind the ligules, otherwise both surfaces glabrous. Panicles to 53 cm, with 5-20 digitate branches; secondary panicles not present in the lower sheaths; branches 7-17 cm, steeply ascending but drooping at the apices. Spikelets 4.5-5 mm, imbricate, green to straw-colored, with 3-4 florets. Glumes ovate, acute; lower glumes 1.3-2.6 mm; upper glumes 2.2-3.7 mm; lemmas 2.8-3.8 mm, lanceolate to ovate, chartaceous, lateral veins sericeous, apices acute to slightly obtuse, minutely emarginate, mucronate; paleas ciliolate over the veins; anthers 1, 0.4-0.6 mm. Caryopses 0.9-1.8 mm long, 0.3-0.4 mm wide, triangular in cross section. 2n = unknown.

Leptochloa chloridiformis is native to Uruguay, southern Paraguay, and northern Argentina. It was introduced in the early part of the twentieth century but has not become established in the Flora region. The only known collections are from Cameron County, Texas, the most recent having been made in the 1940s.

3.   Leptochloa virgata (L.) P. Beauv.
Tropical Sprangletop

Plants perennial. Culms 30-200 cm, erect, occasionally geniculate below, compressed, branched; internodes solid. Sheaths glabrous, scabrous, or sparsely pilose below, hairs never papillose-based; ligules 0.3-1 mm, truncate, firmly membranous, fimbriate or erose, sometimes pilose at the sides; blades 5-45 cm long, 4-10 mm wide, glabrous abaxially, glabrous or sparsely pilose adaxially. Panicles 5-60 cm, with 9-25 usually racemose (rarely subdigitate) branches; secondary panicles not present in the lower sheaths; branches (1.5)3-18 cm, erect to spreading, somewhat flexible. Spikelets 2.5-4 mm, imbricate to distant, with 3-6(8) florets. Lower glumes 1.7-2.9 mm, lanceolate, acute; upper glumes 1.7-3.8 mm, lanceolate to ovate, acute, acuminate, rarely mucronate; lemmas (1.5)2.3-3.6 mm, ovate, chartaceous, veins sericeous, apices usually acute, rarely obtuse, unawned, mucronate, or awned, awns to 11 mm; paleas glabrous; anthers 2, 0.2-0.5 mm. Caryopses 1-1.8 mm long, about 0.5 mm wide, narrowly elliptic to ovate, somewhat laterally compressed. 2n = 40.

Leptochloa virgata is a common neotropical species that extends from the southeastern United States through the West Indies to Argentina. Awn length and lemma pubescence vary continuously and independently, precluding their use in recognizing additional taxa.

4.   Leptochloa fusca (L.) Kunth

Plants annual or weakly perennial. Culms 5-170 cm, prostrate to erect; compressed, often branching; internodes hollow. Sheaths glabrous or scabrous; ligules 2-8 mm, membranous, attenuate, becoming lacerate at maturity; blades 3-50 cm long, 2-7 mm wide, glabrous or scabrous, those of the flag leaves sometimes exceeding the panicles. Panicles (1.5)10-105 cm long, 0.5-22 cm wide, with 3-35 racemose branches, bases of the panicles sometimes remaining enclosed in the upper leaf sheaths at maturity; branches 1.5-20(22) cm, ascending to reflexed. Spikelets 5-12(14) mm, with 6-20 florets. Lower glumes 1-3(4.9) mm; upper glumes 1.8-5.5 mm; lemmas 2-6 mm, sometimes with a dark spot near the base, apices acute to truncate, sometimes emarginate to bifid, unawned, mucronate, or awned; paleas somewhat sericeous along the veins; anthers 1-3, 0.2-2.7 mm. Caryopses 0.8-2.4 mm, elliptic to ovate or obovate. 2n = 20.

Leptochloa fusca grows in warm areas throughout the world. The two American subspecies, subsp. uninervia and subsp. fascicularis, are usually distinct, but they intergrade repeatedly with subsp. fusca.

Uppermost leaf blades exceeding the panicles; panicles usually partially enclosed in the uppermost leaf sheaths; mature lemmas often smoky white with a dark spot in the basal 1/2 ..... subsp. fascicularis
Uppermost leaf blades exceeded by the panicles; panicles usually completely exserted; mature lemmas usually lacking a dark spot (2)
Anthers 0.5-2.7 mm long; spikelets 6-14 mm long; lemmas obtuse, acute, or acuminate, sometimes bifid, light brown to dark green ..... subsp. fusca
Anthers 0.2-0.6(1) mm long; spikelets 5-10 mm long; lemmas obtuse to truncate, usually notched and mucronate, often dark green or lead-colored ..... subsp. uninervia

Leptochloa fusca subsp. fascicularis (Lam.) N. Snow
Bearded Sprangletop

Culms 5-110 cm, prostrate (in small circular clumps) to erect. Blades glabrous or scabrous, uppermost blades often exceeding the panicles. Panicles (1.5)10-72 cm long, 4-22 cm wide, with 3-35 branches, usually partially enclosed in the uppermost leaf sheaths; branches 3-12(22) cm, often spreading. Spikelets 5-12 mm. Lower glumes 2-3 mm, lanceolate, sometimes asymmetric; upper glumes 2.5-5 mm, elliptic to ovate; lemmas lanceolate, smoky white at maturity, often with a dark spot on the basal 1/2, apices acute, mucronate, or awned, awns to 3.5 mm; anthers 1-3, 0.2-0.5 mm. Caryopses 0.8-2 mm.

Leptochloa fusca subsp. fascicularis extends from southern British Columbia and Ontario to Argentina, although it has not yet been reported from Georgia. Coastal populations from Massachusetts to Florida with long lemma awns have been called L. fascicularis var. maritima (E.P. Bicknell) Gleason. They do not merit taxonomic recognition because long awns and salinity tolerance are common throughout the species.

Leptochloa fusca subsp. fascicularis differs from L. viscida, which grows in the same region, in its longer panicles, frequently unawned or mucronate lemmas, and whitish florets.

Leptochloa fusca (L.) Kunth subsp. fusca
Beetlegrass Sprangletop

Culms 40-170 cm, usually ascending to erect, sometimes decumbent and rooting at the lower nodes, often branching at the upper nodes. Blades glabrous or scabrous, not exceeding the panicles. Panicles 15-105 cm long, 2-20 cm wide, sometimes partially enclosed by the upper leaf sheaths; branches (1.5)4-20 cm, ascending to erect. Spikelets 6-14 mm. Lower glumes 1.9-3(4.9) mm, ovate, obtuse to acute, rarely bifid; upper glumes 3-4.7(5.5) mm, obtuse to acute; lemmas 3-4.7(6) mm, light brown to dark green at maturity, without a basal dark spot, apices obtuse, acute, or acuminate, sometimes bifid; anthers 3, 0.5-2.7 mm. Caryopses 1.6-2.3 mm.

Leptochloa fusca subsp. fusca is the most variable of the subspecies. In North America, it is known only from a few specimens collected at scattered locations in California; it may no longer be in the Flora region.

Leptochloa fusca subsp. uninervia (J. Presl) N. Snow
Mexican Sprangletop

Culms (15)25-110 cm, more or less erect, often branching from the aerial nodes. Blades usually densely scabrous on both surfaces, not exceeding the panicle. Panicles 10-57 cm long, (0.5)3-18 cm wide, often ellipsoidal, usually completely exserted from the uppermost leaf sheaths; branches 2-11 cm, mostly ascending. Spikelets 5-10 mm. Lower glumes 1-2.6 mm, narrowly triangular to ovate; upper glumes 1.8-2.8 mm, obovate to widely obovate; lemmas 2-3.6 mm, light brown, dark green, or lead-colored, usually without a basal dark spot, apices usually truncate or obtuse, rarely broadly acute, sometimes bifid, sometimes mucronate; anthers 3, 0.2-0.6(1) mm. Caryopses 1-1.5 mm.

Leptochloa fusca subsp. uninervia is native from the southern United States to Argentina. It may be confused with L. scabra, from which it usually differs in its truncate or obtuse lemmas.

5.   Leptochloa panicea (Retz.) Ohwi

Plants annual. Culms (5)13-150 cm, usually erect, compressed, branching; internodes hollow. Sheaths sparsely or densely hairy, particularly distally, hairs papillose-based; ligules 0.6-3.2 mm, membranous, truncate, erose; blades 6-25 cm long, 2-21 mm wide, glabrous or sparsely pilose on both surfaces. Panicles 8-30 cm, with 3-100 racemose branches; branches 1-19 cm, ascending to reflexed. Spikelets 2-4 mm, distant to imbricate, green, magenta, or maroon, with 2-5(6) florets. Glumes sometimes exceeding the florets, linear to narrowly elliptic, acute, attenuate, or aristate; lower glumes 1.6-4 mm, linear to lanceolate; upper glumes 1.6-3.6 mm, lanceolate; lemmas 0.9-1.7 mm, glabrous or somewhat sericeous, acute to obtuse; paleas glabrous or sericeous; anthers 3, 0.2-0.3 mm. Caryopses 0.8-1.2 mm long, 0.5-0.6 mm wide, nearly round in cross section, with or without a ventral groove, apices acute to broadly obtuse.

Leptochloa panicea is a cosmopolitan species that somewhat resembles L. chinensis, an aggressive weed that has not yet been found in the Flora region. It differs in its sparsely to densely hairy, rather than glabrous or almost glabrous, sheaths and blades. Two of its three subspecies grow in the Flora region.

Glumes linear to narrowly lanceolate, exceeding the florets; lemmas 0.9-1.2 mm long; caryopses without a ventral groove, often somewhat coarsely rugose, the apices broadly obtuse ..... subsp. mucronata
Glumes lanceolate to narrowly elliptic, not or only slightly exceeding the florets; lemmas 1.3-1.7 mm long; caryopses usually with a narrow, shallow ventral groove, smooth, the apices broadly obtuse to acute ..... subsp. brachiata

Leptochloa panicea subsp. brachiata (Steud.) N. Snow
Red Sprangletop

Culms to 150 cm. Ligules 0.9-3.2 mm; blades 2-21 mm wide. Glumes usually not exceeding the florets, lanceolate to narrowly elliptic; lemmas 1.3-1.7 mm, shortly sericeous along the veins. Caryopses 0.9-1.2 mm, widely depressed obovate or obdeltate in cross section, usually with a narrow, shallow ventral groove, apices broadly obtuse to acute. 2n = 20.

Leptochloa panicea subsp. brachiata extends from the southern half of the United States to Argentina. It is common in disturbed and mesic agricultural sites.

Leptochloa panicea subsp. mucronata (Michx.) Nowack
Mississippi Sprangletop

Culms to 110 cm. Ligules 0.6-1 mm; blades 5-9 mm wide. Glumes exceeding the florets, linear to narrowly lanceolate; lemmas 0.9-1.2 mm, glabrous or sparsely sericeous along the veins. Caryopses 0.8-0.9 mm, without a ventral groove, sometimes coarsely rugose, apices broadly obtuse. 2n = unknown.

Leptochloa panicea subsp. mucronata grows in the southern portion of the United States, primarily from Kansas and Missouri through Texas and Louisiana.

6.   Leptochloa nealleyi Vasey
Nealley's Sprangletop

Plants annual. Culms (30)60-250 cm, mostly erect, compressed, sometimes branching from the lower nodes; internodes hollow. Sheaths glabrous, smooth or minutely scabrous; ligules 1.5-3 mm, membranous, truncate, erose, sometimes appearing ciliate because of the hairs at the base of the blades; blades 10-75 cm long, 4-7 mm wide, sometimes with stiff hairs behind the ligules, both surfaces scabridulous elsewhere. Panicles 30-76 cm, with 25-75 racemose branches; branches mostly 1-5(9) cm, steeply ascending to erect, stiff, lower branches sometimes included in the upper leaf sheaths. Spikelets 2.8-3.4 mm, imbricate, with 3-4 florets. Glumes lanceolate, lower glumes 0.7-0.8 mm, acute to narrowly obtuse; upper glumes 0.9-1.3 mm, obtuse; lemmas 1-2 mm, broadly lanceolate, membranous, veins sericeous basally, apices obtuse to acute or apiculate; paleas sericeous along the veins; anthers 3, 0.2-0.4 mm. Caryopses 0.5-1 mm long, 0.4-0.5 mm wide, elliptic to obovate, nearly round in cross section. 2n = 40.

Leptochloa nealleyi is native to coastal Louisiana, Texas, and Mexico; it also grows, but rarely, in Cuba. The species is not established in Arizona, but it was collected once from a farm in the Wellton area (NCU 303513). It is not clear whether the plants were being cultivated or growing as weeds.

The numerous, short, stiffly ascending or erect panicle branches make Leptochloa nealleyi easy to identify.

7.   Leptochloa scabra Nees
Rough Sprangletop

Plants annual. Culms (12)20-125 cm, mostly erect, often strongly compressed, branching; internodes hollow. Sheaths glabrous, smooth to scabrous; ligules 1.5-2 mm, membranous, truncate, erose; blades 25-35(50) cm long, 8-16 mm wide, scabrous on both surfaces. Panicles 8-35 cm, with 50-150 racemose branches; branches (2)5-12 cm, lax, sometimes arcuate, lower branches often remaining enclosed in the upper leaf sheaths. Spikelets 3-4.5 mm, usually tightly imbricate, green but straw-colored when dry, with 2-6 florets. Glumes sometimes mucronate; lower glumes 0.8-1.6 mm, narrowly triangular to lanceolate; upper glumes 1.1-2.1 mm, ovate; rachilla internodes not visible between the florets; lemmas 2.1-2.4 mm, lanceolate to narrowly ovate, membranous, sparsely sericeous along the lateral veins, apices acute, unawned; anthers 0.2-0.4 mm. Caryopses 0.8-1.3 mm long, 0.3-0.5 mm wide, elliptic to obovate, depressed obovate in cross section. 2n = 60.

Leptochloa scabra is a neotropical species that extends into Louisiana and southwestern Alabama. It is often confused with L. panicoides, but it has more, flexuous to arcuate panicle branches, shorter spikelets, and less prominent lemma veins. It may also be confused with L. fusca subsp. uninervia, from which it differs in its acute lemmas, and with L. virgata, from which it differs in its hollow, flattened culms and the complete lack of lemma awns.

8.   Leptochloa chinensis (L.) Nees
Asian Sprangletop

Plants annual or perennial. Culms 15-100 cm, round, glabrous or appressed-pubescent; internodes hollow. Sheaths sometimes flattened below, usually glabrous, sometimes sparsely pilose at the apices; ligules 1.8-5.4 mm, truncate, erose or ciliate; blades (1)5-30 cm long, 4-8 mm wide, glabrous, sometimes scabridulous. Panicles 20-50 cm, with 25-60 racemose branches; branches (1)4-8(14) cm, erect to slightly reflexed, usually straight. Spikelets 2.5-3.7 (4.2) mm, imbricate to somewhat distant, green to tan, with 4-6 florets. Glumes triangular to lanceolate; lower glumes 1.1-1.7 mm; upper glumes 1.6-2 mm; rachilla internodes usually visible between the florets; lemmas 1.2-1.7 mm, ovate to elliptic, glabrous or hairy along and between the veins, apices broadly acute or obtuse; paleas glabrous or hairy; anthers 3, 0.4-0.6 mm. Caryopses 0.9-1.9 mm long, 0.6-0.8 mm wide. 2n = 40.

Leptochloa chinensis is not yet known from the Flora region but it is considered a noxious weed by the U.S. Department of Agriculture because it would probably displace native species in undisturbed mesic sites. Although it resembles L. panicea, L. chinensis differs in its glabrous, or nearly glabrous, sheaths and blades.

9.   Leptochloa viscida (Scribn.) Beal
Sonoran Sprangletop

Plants annual. Culms (3)10-60 cm, prostrate or erect, round or somewhat compressed, often highly branched; internodes hollow. Sheaths glabrous (rarely sparsely pilose near the base), sometimes with a sticky exudate; ligules 1.2-2.5 mm, truncate, erose to lacerate; blades 1-15 cm long, 1.2-5.5 mm wide, glabrous abaxially and adaxially. Panicles 2-17 cm, with 5-23 racemose branches; branches 1-2.5(3.5) cm, stiff, often included in the upper leaf sheaths. Spikelets 4.5-7.5 mm, more or less imbricate, magenta or green, with 2-6 florets. Glumes triangular, acute; lower glumes 1.6-2 mm, acute; upper glumes 2-2.9 mm; lemmas 2.4-3.5 mm, ovate, membranous, sericeous along the lower veins, lateral veins pronounced, apices acute, obtuse, or truncate, awned, awns 0.5-1.5 mm; paleas minutely scabrous along the veins; anthers 3, 0.4-0.5 mm. Caryopses 1.2-1.6 mm long, 0.4-0.5 mm wide, narrowly elliptic to obovate, transversely elliptic in cross section. 2n = 40.

Leptochloa viscida is a Sonoran Desert species that occurs from southern California to southwestern New Mexico and south into adjacent Mexico. It differs from L. fusca subsp. fascicularis, which grows in the same region, in its consistently short-awned lemmas, smaller panicles, often prostrate and much-branched growth habit, and often reddish florets.

10.   Leptochloa panicoides (J. Presl) Hitchc.
Amazon Sprangletop

Plants annual. Culms (7)45-110 cm, often geniculate below, usually ascending to erect above, rarely branching at the base, often branching distally; internodes hollow. Sheaths glabrous, margins occasionally sparsely ciliate on the basal 1/2; ligules 2.2-3.8 mm, membranous, truncate, somewhat erose; blades 4-20 cm long, 4-8 mm wide, both surfaces smooth or scabridulous. Panicles 20-35 cm, with 20-30(90) racemose branches; branches 2.5-7 cm, ascending, mostly stiff. Spikelets 4-5 mm, usually somewhat imbricate, with 4-6(7) florets. Lower glumes 0.9-1.9 mm, usually lanceolate, sometimes falcate, acute; upper glumes 1.8-2.3 mm, ovate, acute to obtuse; lemmas 2.4-3 mm, narrowly elliptic to ovate, membranous, midveins and lateral veins sericeous basally, lateral veins prominent, excurrent, apices acute to broadly acute, unawned, sometimes mucronate; paleas glabrous; anthers 3, 0.6-0.8 mm. Caryopses 1.1-1.4 mm long, 0.7 mm wide, elliptic, depressed obovate in cross section. 2n = 20.

Leptochloa panicoides is native from the central Mississippi and Ohio river drainages south through Mesoamerica to Brazil. It usually grows in somewhat mesic habitats. It has been reported from two counties in Texas, but no specimens documenting the reports have been found so they are not shown.

Nicora (1995) merged Leptochloa panicoides with L. scabra, but the two differ consistently in the number of panicle branches, spikelet length, and prominence of the lemma veins.