Azolla false-fern, Azolla, Moss of the fes, Azolla filiculoides: to plant, cultivate, multiply

It is called fairy moss, it floats on the water in dense mats, of a dull green verging on reddish. Coming from South America, the Azolla false-fern is none other than a small fern adept in wetlands.

Azolla false-fern, Azolla, Moss of the fes, Azolla filiculoides


N. scientific Azolla filiculoides

Family Salviniaces

Origin Asia

Bloom june september

Typefloating plant

Vegetationannual plant

Foliage disappears in winter

Heighta few centimeters

Plant and cultivate

hardiness not hardy

Exposition sun, light exposure

Solbassin, sea

Acidity neutral

Humidity wet

Utilisationaquarium, pond, bio-fertilizer, animal feed, limits the development of mosquitoes



Mockfog Azolla

A tiny fern floating on the water

She lives with the known small duckweed, Leave mines, plant covering ponds and basin with a soft green carpet. The Azolla false fern, family of the Salviniaceae, installs its dark green to reddish carpets on the surface of stagnant water. Small, it develops stems of one centimeter at most, branched in a horizontal plane, covered with interlocking scales. Fine roots plunge into the water. Side by side, these ferns float, multiply, form a dense coversprinkled with shiny droplets.

Small, but fast and invasive

Like any fern, Azolla multiplies by spores, large and small, produced in the fall, giving rise to new individuals at the end of winter. But the Azolla is especially remarkable for its vegetative propagation. Its fine stems grow at full speed, branch out, unfold, all similar to each other. Their population can double in a week. Especially when the temperatures are mild, between 22 and 27°C. They have with it a precious ally to grow so quickly: Anabaena azolla, nitrogen-fixing cyanobacterium, established well sheltered in cavities within the leaves. Their symbiosis allows the Azolla to grow efficiently. The slightest gust of wind, a snorting bird, breaks and fragments the fragile stems. They then continue to multiply even more.

An unexpected guest

The Azolla takes place in a pond, a ditch, a calm body of water, covers it with a homogeneous carpet. Under his shadow, a beetle decides to take flight, to find a site with clearer and brighter waters. But he will take off with a fragment of the little fern clinging to the hairs of his feet. Thus the Azolla travels, clandestine passenger of birds, small mammals, batrachians, moving from one water point to another.

Winter alone will mark a break. The Azolla does not like the cold. It gradually disappears with the advance of winter. The last individuals hidden in sheltered nooks will disappear with a long-lasting and intense frost.

Sometimes feared, sometimes cultivated

Imported in Europe at the end of the 19th century, the Azolla poses serious problems of eutrophication of wetlands. It forms such a dense carpet on the surface of the waters, piling itself up on several floors, that it completely blocks out the sun. At his death, the excess matter organicrich in nitrogen, deposited in the bottoms, will further accentuate eutrophication, and will sign the end of the pond’s biodiversity.

Yet sometimes the Azolla is sought after. And cultured. As bio-fertilizer in rice fields, but also as ground cover smothering weeds like mosquito larvae. Opportunities in animal feed have also emerged, for its richness in proteins, amino acids, vitamins and mineral elements.

And especially the Azollas have exceptional heavy metal binding properties. Properties that can be used for filter polluted waterand therefore recycle these ferns, recover and reuse these metals.

So small, and so prolific, the Azolla is a questioning fern. Invasive, it has a formidable predator, a beetle from America. Is it risky to introduce it in Europe? Cultivating it could unbalance entire ecosystems, displacing essential elements from the soil? Introducing it into animal feed chains requires monitoring its heavy metal concentrations?

Different species Azolla

  • Azolla carolinianaCarolina mosquito

Source: Au Jardin, conseils en jardinage by

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