Flora of New Zealand Series

Floating aquatic ferns with short stems lacking roots. Lvs in whorls of 3, dimorphic: 2 green, floating, entire, elliptic, c. 0.5-2.5 cm long, papillate on upper surfaces, with anastomosing veins; 1 submerged, highly branched and appearing root-like. Mega- and microsporangia borne separately in stalked sporocarps on the submerged lf. Spores trilete.

c. 10 spp., tropical and warm temperate, mostly in tropical America and Africa, also Europe and Asia. Naturalised sp. 1.

Salvinia spp. are widespread in the tropics and some have become naturalised as aggressive weeds in tropical and warm temperate regions. They rapidly form large floating mats in slow-moving or still water and choke other aquatic plants.