Cyperus laxus Lam.

Global description

Cyperus laxus is a vivacious sedge growing from a short rooted rhizome. The stem is trigonal, the leaves arranged tristically have sheaths nested at the base of the stem, the blade has a central gutter and is shorter than the stem. The inflorescence is formed of large umbels with long, fine rays ending in small umbellules with about twenty fasciculate lanceolate spikelets.

General habit

Cespitose and vivacious plant, 20 to 60 cm high.

Underground system

Short tuberous rhizome covered with dark scales. Fibrous roots.

Stem

The stem is trigonal, with obtuse angles, 2 to 4 mm in diameter. It is smooth and glabrous, green and shiny.

Leaf

The leaves are simple, linear lanceolate located at the base of the plant and arranged tristically. At the base is a closed, trigonal, glabrous sheath. The blade is less than or equal to the length of the stem, linear, 5 to 8 mm wide and has a characteristic gutter in the middle part. The summit is abruptly acute or acuminate, the margin is entire and smooth. Both sides are glabrous.

Inflorescence

The inflorescence is a large umbel of 10 to 30 cm in diameter, very loose, consisting of 8 to 12 fine rays 10 to 23 cm long, carrying at their end an umbellule of 7 to 9 short rays bearing ultimate umbellules of 3 to 6 even shorter rays. The rays are very spread out or even slightly drooping. At the base of the umbel are 7 to 10 leaf-like involucral bracts, similar in shape to the leaf blade, 20 to 60 cm long and 4 to 12 mm wide, often longer than the primary rays of the main umbel. Characteristically, the summit of the bracts is abruptly acuminate and terminates in a tapered tip. At the base of the umbellules are some linear bracts shorter than the rays. The spikelets of the umbellules are grouped in fascicles of 3 to 9. They are lanceolate, 6 to 12 mm long and 3 mm wide, including 10 to 24 flowers. The rachillet is closely winged. The glumes are oval, abruptly acute and mucronate, green on the back and hyaline or brownish on the sides, with 5 veins. 3 evergreen stamens, trifid style.

Fruit

The fruit is an oboval achene, a concave-faced trigononal with a slender base and a slightly apiculated apex, 1.5 mm long and 1 mm in diameter. The tegument is smooth and dark brown in color. The base of the style is very small.
 

Origin

Cyperus laxus is native to South America.

Worldwide distribution

The species is present in the humid tropical regions of the American continent and the Caribbean. It is also present in Equatorial Africa and Asia.

https://www.gbif.org/species/2713471