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Azolla (Azolla filiculoides and others)


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.

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.

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 plays symbiotic host 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.


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. The rabbits will eat it willingly, especially if a handful is mixed with their usual feed.

Worms love it 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.

We had two plastic tubs in which we grew our Azolla. Over time though, we grew to love using it so much that it now has a dedicated tub in the aquaponics.

You don’t need much water to grow it, we grow ours about 2 cm, that’s all.We don’t get many mosquitoes growing in the tubs because the dense growth seems to provide 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 put it in a new container of water with a little fertilizer mixed in. You could be surprised by the speed at which it covers the water’s surface.


Azolla is an aquatic fern

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! Big handfuls of it around potted plants make for an water laden, insulating blanket that breaks down quickly to release its nutrients.

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.

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.


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