Pseudoraphis spinescens

Pseudoraphis spinescens, called spiny mudgrass or Moira grass is a rhizomatous and stoloniferous aquatic or semi-aquatic perennial grass, with ascending stems forming loose, floating mats in water to 1 m deep or more, or with stems to 50 cm high when not submerged. Moira grass (Pseudoraphis spinescens) was first described in 1810 by Robert Brown as Panicum spinescens, and subsequently transferred to Pseudoraphis by Joyce W. Vickery in 1950.

Pseudoraphis spinescens is native to floodplains in Asia and Australasia, it is a C4 species, requiring seasonal cycles of prolonged, deep flooding interspersed with drying to achieve maximum growth and reproduction. Between flood events, P. spinescens forms a deep thatch of collapsed dry stems until flooding recurs and growth recommences. A study in southeastern Australia found that P. spinescens does not have a viable long-lived seed bank in floodplain soil, presumably regenerating from vegetative propagules and rootstocks.

In the Murray-Darling Basin, prior to regulation of the Murray River, extensive Pseudoraphis spinescens dominated floodplain marshes existed in areas that were typically seasonally flooded for 5–9 months duration in most years, to a minimum water depth of 0.5 m, and completely dry during late summer and autumn.

Pseudoraphis spinescens is an important species in floodplain marsh ecosystems, providing habitat and food for a range of fauna including birds, frogs, fish and insects, and key ecosystem functions such as nutrient cycling and primary productivity.