Azolla - Salviniaceae

Azolla filiculoides Lam.

Photo: MA. Hyde

Photo: BT. Wursten

Photo: BT. Wursten






Common name

Red water fern Water fern


Rhizomes horizontal, branched, up to 25-35 mm long, bearing roots singly or in clusters of 2-3. Leaves closely overlapping, 2-lobed, each lobe 0.5-1.5 mm long, silvery-green, turning red in winter; dorsal lobe broadly ovate to almost circular, apex rounded, margin translucent, thickly papillate; ventral lobe like dorsal lobe but completely translucent. Plant heterosporous.


A fairly frequent well-naturalised species. It differs from A. nilotica in having 1-3 roots per node whereas A. nilotica has numerous (5 or more) roots per node. The other native Azolla, A. pinnata, has 2-3 roots per node, but the plant is more noticeably pinnate, the leaves are smaller and more acute at the apex and the plant is never reddish.
Recent literature (Roux et al., 2011) describes the resemblance of A. filiculoides to another introduced species in South Africa, A. microphylla. A. microphylla has ± dichotomously branched rhizome (irregular, not noticeably pinnate in A. filiculoides) and roots that are hairy & not curled at the tip (not hairy & curled at the tip in A. filiculoides). More research to establish wether A. microphylla also occurs in Zimbabwe is needed.


filiculoides: resembling a fern (from the Latin, filicum for a fern); unclear reference since Azolla does not coincide with the image that one has of a fern.


In slow-moving water, such as in dams and ditches and slower-flowing parts of streams and rivers.

Distribution worldwide

Africa; native to tropical S America (Argentina, Brazil, Uruguay and Peru), but now widespread as a weed in Europe, N America, Australia and New Zealand.

Distribution in Africa

Egypt, Lesotho, Morocco and Western Sahara, South Africa, Zimbabwe.

Growth form



  • Burrows, J.E. (1990) Southern African Ferns and Fern Allies. Frandsen, Sandton. Page 83. (Includes a picture).
  • Crouch, N.R., Klopper, R.R., Burrows, J.E. & Burrows, S.M. (2011) Ferns of Southern Africa, A comprehensive guide. Struik Nature. Pages 214 - 215. (Includes a picture).
  • Jacobsen, W.B.G. (1983) The Ferns and Fern Allies of Southern Africa. Butterworths, Durban and Pretoria. Pages 494 - 495. (Includes a picture).
  • Roux, J.P. (2001) Conspectus of Southern African Pteridophyta.Southern African Botanical Diversity Network Report, 13 Page 179.
  • Roux, J.P. (2009) Synopsis of the Lycopodiophyta and Pteridophyta of Africa, Madagascar and neighbouring islands. Strelitzia 23, South African National Biodiversity Institute, Pretoria. Page 58.