Salvinia (a complex consisting of Salvinia auriculata Aubl., Salvinia biloba Raddi, Salvinia herzogii de la Sota, Salvinia molesta D.S. Mitch)

Family: Salviniaceae

Common names:  giant salvinia

Disseminule:  Spores, stem fragments

Brief description

Free-floating perennial aquatic ferns with stems just below water surface and floating leaves (fronds). Upper surfaces of floating leaves bear eggbeater-shaped hairs. Primary growth form has small, flat leaves; tertiary growth form is a mat of crowded, folded leaves.

Identification remarks

Although the members of the Salvinia complex are difficult to distinguish, the eggbeater-shaped hairs are diagnostic for this group; the non-noxious Salvinias do not have them.

Distribution

Widespread (particularly Salvinia molesta) throughout the tropics and subtropics, in South America, Africa, India, Southeast Asia, Australia, New Zealand, and the Pacific islands.

Native to tropical South America.

Habitat

Tropical to warm-temperate climates, in still and slow-moving waters of ponds, rivers, marshes, and rice fields.

General information

The Salvinia complex is a closely related group of floating ferns. S. molesta is the most notorious and widespread; originally used as an ornamental aquarium plant, it has now become naturalized worldwide. S. auriculata reportedly infests Lake Kariba in Africa and waters and rice fields in Sri Lanka. The tertiary growth form of these plants can very quickly form dense mats that may be more than 2 m thick. These mats block light and oxygen, displacing native plants. The mats also decrease water quality, and interfere with hydroelectric plants and recreational use. S. biloba and S. auriculata may produce fertile spores, but S. molesta and S. herzogii are sterile hybrids. The chief means of reproduction is vegetative. Buds form at stem nodes, and stem fragments are dispersed by wind, water currents, and human activities such as boating. Cyrtobagous salviniae is a weevil that has been used successfully to control S. molesta in several countries.

Salvinia molesta.  Photo: © Barry A. Rice/The Nature Conservancy

Salvinia molesta.  Photo: © S. Navie

Salvinia molesta.  Eggbeater-shaped hairs.  Photo: © Barry A. Rice/The Nature Conservancy

Salvinia molesta.  Secondary habit.

Photo: © M. Julien

Salvinia molesta. Tertiary habit.

Photo: © S. Navie