Azolla (Azolla filiculoides and others)

Azolla forms dense mats across the surface of water.
Azolla forms dense mats across the surface of water.

Common names: Azolla, Duckweed, Mosquito Fern

Taxonomic name: Azolla species

Family: Salviniaceae

Uses: Livestock food, compost, nitrogen fixing

Area of origin: Global

Warnings: None

Azolla is a genus of aquatic ferns that can have an important role in a garden. Azolla filiculoides or ‘Red Azolla’ is the most common species around here, but the rest are pretty similar. I first wrote about Azolla in Grass Roots Magazine No. 257 Feb/March 2020  in a little article titled ‘Amazing Azolla’.

What makes it good for gardens?

Azolla is simple to grow – just water and sunlight is enough, though it does like a few nutrients too. It does like phosphorous and a deficiency in this can be seen in slower growth and red tinged leaves.

Azolla can double its mass in 3 days! Wow! that’s really important because it can easily supply us with a lot of organic material. Of course, conditions apply. In non-perfect conditions, it can take longer, maybe up to two weeks. This means you have to buy less mulch or compost for your garden.

Azolla ferns also play symbiotic hosts to a species of bacteria that fixes nitrogen from the atmosphere (and I suppose the water too). Fixing nitrogen into the biomass means a more nutritious addition to your garden mulch.

Azolla leaves.
Prolific and fast growing

Azolla is rich in protein (25 – 30% dry weight!), amino acids and minerals such as iron, calcium, phosphorous, potassium, copper and magnesium. It’s also low in carbohydrates and contains Omega 3 Fatty Acids. People can eat it (yuck!) but it’s best fed to pets and livestock. Our chickens love it in Summer but tend to go off of it in the colder weather. When we had rabbits, they would eat it willingly, especially if a handful or two was mixed with their usual feed.

Worms love Azolla too, especially when it’s added to worm farms in Summer. They can go to work on the bacteria straight away while the rest breaks down. The high levels of protein in Azolla makes for fat worms.

We have two plastic tubs in which we grow our Azolla.. You don’t need much water to grow it, we grow ours about 5 cm, that’s all. We don’t get many mosquitoes growing in the tubs because the dense growth to provides a barrier to them. There are usually a couple around, but nowhere near the amount I was expecting. As a precaution, though, we grow it away from the house.

The occasional addition of a little urine, worm wee, or Seasol gives it the nutrients that it needs to thrive.

Propagation is dead easy as well. Just grab a handful and grind it up into smaller pieces and put it in a new container of water with a little fertilizer mixed in. The best fertilizer to get things going ios definitely chicken poo. Add couple cf cupfuls to the tub and you could be surprised by the speed at which the Azolla covers the water’s surface.

Azolla roots can float or anchor in soil.
Azolla roots can float or anchor in soil.

To use it in the garden, just apply handfuls directly to where you want it to go. You could dig it in too, but I’m too lazy to do that!

To feed it to your animals, just give it to them directly, the individual plants are small enough for chickens to eat and large enough for rabbits and goats and the like. For worms, just throw handfuls onto the beds and let its wet goodness feed them up.

Azolla is such a big deal when it comes to sustainable farming that there’s a foundation dedicated to it, The Azolla Foundation. There’s also an organisation in the Philippines that promotes its use, it’s called Azolla Philippines.

Azolla makes an incredible Summer mulch for pot plants.
Azolla makes an incredible Summer mulch for pot plants.
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