Common Australian Garden Weeds

Azolla spp.

Scientific name: Azolla spp.


Population of red azolla (Azolla spp.) floating on the water surface.


Closer view of the ferny nature of this species.


Close-up of red azolla showing the tiny overlapping scale-like leaflets.

Common name: Red azolla, azolla

Family: Azollaceae

Origin:

Native of North America (ie. Azolla filiculoides).

Habit:

Floating aquatic fern, which multiplies rapidly by self-division to form dense mats on the water surface.

Habitat:

Azolla spp. require fresh still water such as dams, ponds, lakes, drains and suburban waterways.

General description:

Stems and leaves
Stems zigzag horizontally, usually covered by over lapping, leaves. Stems are brittle and break easily. The tiny, two-lobed (bi-lobed), scale-like leaflets are arranged in 2 rows and are green to greenish-red to red in colour. Plants are usually less than 3 cm in size.

Flowers and fruit
Tiny spherical sporocarps (ie. stalked fruit cases containing sporangia or spores) are produced in the leaf axils on the underside of the leaves.

Distinguishing characteristics:

Small aquatic herbaceous plant with zig-zaging stems and tiny, two-lobed leaflets arranged in two rows. The only plant with any resemblance is Lemna spp. (duckweeds). This weed is small and also floats on the water, however it is unbranched and pale green in colour.

Noxious status:

Not noxious.

Sources:

Clifford, H.T. and Constantine, J. (1980). Ferns, Fern Allies and Conifers of Australia: a Laboratory Manual. University of Queensland Press, Brisbane.

Jones, D.L. and Clemesha, S.C. (1989). Australian Ferns and Fern Allies. 3rd Edition. Reed Books, Sydney.

Kleinschmidt, H.E., Holland, A. and Simpson, P. (1996). Suburban Weeds. 3rd Edition. Department of Primary Industries, Brisbane.