Azolla, nature's Swiss army knife

There is a very select group of plants capable of changing the face of the world. Azolla, our tiny floating fern, is one of them.
At first glance, it looks lovely but nothing spectacular: small leaves just a few millimeters wide, floating on the surface of ponds or pools and forming a beautiful velvety carpet, ranging from green to deep red.
But behind this apparent simplicity lies one of the most fascinating stories of partnership, growth, and even... the planet’s climate!
It is clearer now why I chose it to create the name Aquazolla...

 

 

A partnership between a fern and a blue-green alga

Azolla lives in partnership with a blue-green alga called Nostoc azollae (formerly Anabaena azollae). Much like lichen, which is a partnership between an alga and a fungus.
When you buy Azolla on the site, you actually get two plants for the price of one!
Nostoc azollae lives inside the tiny leaves of Azolla, in cavities specially made to house it.
This blue-green alga fixes nitrogen from the air for the benefit of the plant which, in return, offers shelter, carbon, and protection.
This partnership is so close that it is passed down from generation to generation: each spore of Azolla already contains its symbiotic blue-green alga, which is rare in the plant world.
Result: a plant able to grow in waters almost free of nitrates, as it draws its own nitrogen from the air.
A tiny living power station that depends only on sunlight and water.
Self-sufficient in nitrogen (like the bean), Azolla is therefore one of the plants richest in protein. We will return to this later.
In fact, in recent years, it has been discovered that Azolla hosts other tiny living things, all playing a role in its functioning, making it in reality a highly complex plant system and probably unique.

 

 

The Azolla event: when a single small plant changed the Earth’s climate!

About 50 million years ago, during the Eocene, the Earth had a tropical climate reaching the poles.
The Arctic Ocean, isolated and made up of fresh water on the surface, was then invaded by vast carpets of Azolla.
For 800,000 years, it grew, then its colossal mass died and sank.
At the bottom of the water, without oxygen, dead tissues do not rot and remain trapped forever. So a huge amount of carbon disappeared permanently beneath the waters.
Researchers estimate (no eyewitnesses found!) that this “Azolla event” caused a drastic drop in atmospheric CO₂, thus helping to cool the Earth’s climate for good.
Our little fern therefore helped shift the planet from a tropical world to a temperate one. Like a giant!

 

 

A natural and lasting resource

Even today, Azolla provides great help to people.
In many countries in Asia and Africa, it is grown to feed livestock, ducks, fish, and even pigs.
Rich in protein as we saw above (up to 30% of its dry weight), minerals, and vitamins, it is an excellent ecological alternative to soybean meal for cows.
And since it fixes nitrogen from the air, it can be used as a natural green manure in rice fields: it enriches the soil while reducing the use of chemical fertilizers.
A true ally of lasting farming.

 

 

A useful plant in aquariums and ponds

Here at home, Azolla is easily grown in ponds and open aquariums.
It forms a floating plant carpet on the water’s surface that limits the light available to algae, while offering shelter to many tiny living things and small animals without backbones.
It is also known as the “mosquito fern,” because its cover stops mosquito larvae from reaching the air to breathe. It literally suffocates them!
And above all, it is a changing and living plant: depending on light and temperature, its leaves change from green to reddish-brown, forming real colorful mosaics.
This change is due to the production of anthocyanins, protective pigments.
In good conditions, Azolla can double its mass in 2 to 3 days!
But its incredible growth speed can also cause problems: without control, it can cover an entire pond and block light from the whole water column and the life within.
What limits its growth? Its hunger for phosphorus.
Since it takes nitrogen and carbon from the air freely and without limit, it is the phosphorus it draws from the water that can run short for its wild growth. And since excess phosphorus encourages algae, Azolla is, in fact, a formidable weapon against algae, literally starving them.

 

A fussy plant

As soon as you receive your stock, Azolla will surprise you.
During the journey, it will seem to have fallen apart! The fronds usually break into crumbs, and its black “roots” sadly lie at the bottom of the bag.
All this is normal. This breaking up of Azolla when handled is precisely its natural way of multiplying: each “crumb” then gives a new whole plant, and so on. This is how it spreads so quickly.
And those roots that fall off? In truth, they are false roots. These black threads always fall off when the plant changes environment, so it can grow others, better suited and younger, in the new place.
But it remains fussy: sometimes it does not like the place and refuses to grow. It will then start again one day, from a “crumb” left on the surface (or at the bottom in winter), and you will not always know why!

 

A beautiful, extraordinary plant, a marvel of life, a curiosity that does as it pleases, and a true ecological tool: now you understand why it is our mascot here at Aquazolla!