Paspalum dilatatum Poir.

dallis grass, Australian water grass


Info

Subfamily: Panicoideae
Genus etymology: Paspalum = "millet" [Greek] some species are used as cereals
Species etymology: dilatatum = "spread out / diliated" [Latin] perhaps refering to the spreading inflorescence branches
Photosynthetic type: C4 (warm season)
Nativity: naturalized - intentional
First recorded in Hawaiʻi: 1903

Map

 Distribution of Paspalum dilatatum in Hawaiʻi.
 Distribution of Paspalum dilatatum in Hawaiʻi.

Inflorescence

Paspalum dilatatum Inflorescence
Paspalum dilatatum Inflorescence

Plant

Paspalum dilatatum Plant
Paspalum dilatatum Plant

Habit

Paspalum dilatatum Habit
Paspalum dilatatum Habit

Spikelets

Paspalum dilatatum Spikelets

Description

Plants perennial; cespitose, rhizomatous, rhizomes short (less than 1 cm), forming a knotty base. Culms 50-175 cm, erect; nodes glabrous. Sheaths glabrous or pubescent, lower sheaths more frequently pubescent than the upper sheaths; ligules 1.5-3.8 mm; blades to 35 cm long, 2-16.5 mm wide, flat, mostly glabrous, adaxial surfaces with a few long hairs near the base. Panicles terminal, with 2-7 racemosely arranged branches; branches 1.5-12 cm, racemose, divergent; branch axes 0.7-1.4 mm wide, winged, glabrous, margins scabrous, terminating in a spikelet. Spikelets 2.3-4 mm long, 1.7-2.5 mm wide, paired, appressed to the branch axes, ovate, tapering to an acute apex, stramineous (rarely purple). Lower glumes absent; upper glumes and lower lemmas 5-7-veined, margins pilose; upper florets stramineous. Caryopses 2-2.3 mm, white to brown. 2n = 20, 40, 50-63.
(Description source: Barkworth, M.E., Capels, K.M., Long, S. & Piep, M.B. (eds.) 2003. Flora of North America, north of Mexico. Volume 25. Magnoliophyta: Commelinidae (in part): Poaceae, Part 2. Oxford University Press, New York. 783 pp http://floranorthamerica.org/Paspalum_dilatatum )

Perennials; culms tufted, erect or ascending from decumbent base, sometimes rooting at lower nodes, 4-12 dm tall, glabrous or nodes sometimes slightly villous, compressed. Sheaths 6-15 cm long, compressed, usually long-hispid at throat and along margins near base, the basal ones usually densely villous; ligule 3-5 mm long, membranous, bluntly triangular; blades flat, 10-20 cm long, 5-15 mm wide, midrib slightly keeled, margins slightly scabrous, apex acute. Racemes 3-5, ascending or drooping, 5-8 cm long, arranged along upper 6-12 cm of primary axis, long-hispid near base, rachis flat, winged, 1-1.5 mm wide, margins slightly scabrous, sometimes undulate; spikelets paired, imbricate, depressed plano-convex, ovate, 3-4 mm long, apex acute; first glume absent, second glume and first lemma alike, ovate, 3-4 mm long, (3-)5-7-nerved, midnerve prominent, sparsely short-pilose, margins silky pilose, apex beaked; second lemma chartaceous to indurate, ovate, slightly convex, ca. 2.5 mm long, ca. 2 mm wide, faintly 3-nerved, glabrous, margins involute, apex obtuse; palea similar to lemma, flat to concave, 2-nerved. Caryopsis reddish brown, broadly elliptic, compressed, ca. 2 mm long, ca. 1.5 mm wide. [2n = 40, 50-63.]
(Description source: O’Connor, P.J. 1990. Poaceae, pp. 1481–1604. In: Wagner W.L., Herbst D.R. & Sohmer S.H. (eds.)., Manual of the flowering plant of Hawaiʻi. Vol. 2. University of Hawaii Press & Bishop Museum Press, Honolulu )