Oplismenus is a small genus of annual and perennial grasses in the family Poaceae (order Poales), commonly known as basketgrass. The genus is distributed throughout the tropics and subtropics, and into some temperate regions, with species found across the Americas, Africa, Asia, and Australia.
Members of the genus are characteristically scrambling or trailing herbaceous plants. Their stems creep along the ground and can produce roots at the nodes, allowing the plants to spread vegetatively across the forest floor. Leaf blades are lance-shaped to ovate and covered in scattered hairs; the leaf sheaths are similarly hairy. Unlike many of their relatives in the grass family, Oplismenus species use C3 photosynthesis and are shade-adapted, typically occupying the floors of forests and other shaded habitats. Annual species die back during cooler or drier months, while perennial species show considerably greater environmental tolerance.
The taxonomy of the genus has long been contested. Over 100 species names have been proposed, but as of 2016 only 7 are officially recognised. A discriminant analysis published in 1978 found high morphological overlap among many described entities and proposed recognising just five species; a monograph by German botanist Ursula Scholz in 1981, based on examination of over five thousand specimens, recognised nine species and 18 infraspecific taxa. Some species, notably O. hirtellus, have numerous recognised subspecies reflecting variation across wide pantropical ranges.
The most familiar species include O. hirtellus, a widespread pantropical form grown in variegated cultivars as a houseplant in Europe; O. undulatifolius, which extends into temperate East Asia; O. compositus, ranging across the Americas, Africa, Asia, and Australia; and O. burmannii, a pantropical species. Several Australian species have been promoted for revegetation of shady or wet sites and for wildlife gardens, though some display invasive potential outside their native range. All members of the genus are edible to livestock.
Etymology
The genus name Oplismenus is derived from the Ancient Greek hoplismenos (ὁπλισμένος), meaning "armed". This refers to the awned glumes of the flower spikelets, which give the inflorescence a bristly, armed appearance. The name was established by Palisot de Beauvois in 1810, though the independent name Orthopogon (Robert Brown, also 1810) was later set aside; Oplismenus was declared a nomen conservandum (conserved name) in 1978.
Distribution
Oplismenus occurs throughout the tropics and subtropics of the Americas, Africa, Asia, and Australia, with some species — notably O. undulatifolius — extending into temperate regions. Individual species vary greatly in range: O. burmannii and O. compositus are pantropical to near-pantropical, while O. thwaitesii is restricted to Sri Lanka. In Australia, species such as O. hirtellus are widespread in coastal and humid inland forests.
Ecology
Members of the genus are characteristically plants of shaded habitats, most commonly growing on forest floors or in dense undergrowth. Annual species complete their lifecycle within a single growing season and die back during cooler or drier periods; perennial species persist year-round and spread by stem nodes rooting at the ground. Oplismenus uses C3 photosynthesis, distinguishing it from many other tropical grasses that use C4. Several species have demonstrated invasive potential outside their native ranges, particularly in disturbed forest understoreys.
Taxonomy Notes
The genus was described simultaneously and independently by two botanists in 1810: Palisot de Beauvois (as Oplismenus, in Flore d'Oware et de Benin) and Robert Brown (as Orthopogon, in Prodromus Florae Novae Hollandiae). Because Oplismenus had been universally adopted, it was declared a nomen conservandum in 1978. Species delimitation within the genus remains unsettled: morphological analysis has repeatedly found extensive overlap between described species, particularly in Australia and the Americas, with estimates of recognised species ranging from 5 to over 9 depending on the authority. GBIF currently accepts 3 descendant taxa under the genus.
Cultivation
Variegated cultivars of O. hirtellus (particularly the cultivar 'Variegatus', with white-striped leaves) have been grown as trailing houseplants and hanging-basket subjects in Europe and temperate regions. They thrive in indirect light, consistent moisture, and moderate temperatures — conditions that mirror their natural forest-floor habitat. In Australia, locally native species have been used in revegetation and land reclamation projects in shaded or moist sites, and have been promoted as lawn-grass alternatives in wildlife gardens. All species are palatable to livestock.
