Echinochloa stagnina (Retz.) P.Beauv.

Global description
 
Echinochloa stagnina is a big herbaceous plant, generally perennial, which can form dense mats with its long creeping rhizomes and its extensively decumbent stems that root at the nodes. The stems are robust and reach 2 m in height in the sections that are erect. The leaves are linear, narrowed at the base and with tapered tip end and scabrous margins. The ligule is marked with a stiff fringe of cilia, at least on the lower leaves. The inflorescence is a terminal panicle, erect or hardly curved, that can reach 35 cm in length. It consists of a series of spike-like racemes inserted along an axis which can be braced against each other or regularly spaced, hence its shape, which varies from oval to pyramidal. The spikelets are arranged in 4 rows. Racemes have oblong ovoid spikelets ending in a more or less long ridge, up to 2 cm, arranged in 4 rows. Each spikelet contains 2 flowers, and only the external is fertile. The seed is flat and obovoid, about 2.5 mm long.
 
General habit
 
Tall vivacious robust and vigorous stoloniferous grass, measuring between 30 cm and 2 m high. It can behave as an annual
 
Underground system
 
The roots are fasciculate; the plant develops stolons and rhizomes.
 
Culm
 
The culm is robust. It measures up to 2.5 cm in diameter at the base and the runners can measure up to 10 m long. It is spongy, glabrous. Prostrate and branched at the base, it is rooted at the nodes. It then straightens and remains simple. The lower nodes are pubescent. It is an extensively rhizomatous, with creeping submerged or floating rhizomes.
 
Leaf
 
The sheath is glabrous, margin often dotted with a few stiff hairs in its upper part. The ligule is marked with a fringe of stiff cilia that may be missing on the upper leaves. The leaf blade is flat, extensively linear, narrowed at the base, with tapering tip. It measures 10 to 45 cm long and 3 mm to 2 cm wide. It is hairless, except some tuberculate bristles, more or less scabrous. The margin is cartilaginous and scabrous. Midrib is white in general.
 
Inflorescence
 
The inflorescence is a large terminal panicle, 6 to 35 cm long. It consists of an erect or slightly curved axis, on which 5 to 30 spike-like racemes are disposed, whose length, crossing towards the base, vary from 1,75 to 7 cm and which are often arranged unilaterally. The main axis is angular with scabrous edges. The axis of the racemes are scabrous on the margin and have stiff bristles. The inflorescence has variable shapes. The racemes can be side by side, overlap or be spaced apart from each other. The general shape varies from oval to oblong or pyramidal. The spikelets are arranged in 4 rows.
 
Spikelet
 
The spikelets are oblong ovoid, 3.5 to 6 mm long, dorsoventrally flattened, slightly convex on the back, extended by a long edge (4 mm to 2 cm), pubescent hispid, green or tinted purple. The glumes are unequal, membranous, scabrous on the veins, ciliated. The lower glume, ovoid pointed, covered by 3 to 5 ribs, is equal to or slightly greater than half the length of the spikelet. Upper glume, ovoid ended in fine tip, covered by 5 ribs, is as long as the spikelet.The spikelet contains 2 flowers: an internal sterile or male flower, with an inferior lemma extended by a scabrous ridge that reaches 25 mm long, an external fertile flower with 3 stamens with purple anthers, narrowly oblong-lanceolate, with sharp end and ciliated, of straw yellow color at maturity.
 
Grain
 
The grain is obovoid shape, flattened convex, with obtuse end. It measures approximately 2.4 mm long and 1.4 mm wide.

Origin

Echinochloa stagnina is native to tropical Africa.

Worldwide distribution

This species occurs mainly in tropical Africa and Madagascar. It is also localy present in Asia.

https://www.gbif.org/species/2702806