by Marcia Wilson

Tiny and mighty

In the bitter teeth of winter, some plants shine.

Peeking through the dry stalks of dormant cattails and reeds rest quiet pools of a tiny plant that shines like jewelry and changes its colors from bright blue-green in summer to a rose-petal pink in winter.  Meet the Azollas, the aquatic ferns native to Washington State. The City of Tacoma is delighted to see this little resident in the Clover Park Technical College wetlands.  It is a small plant with a big ecological role.

What is it

Azolla sp., also known as

• Pacific Water Fern
• Duck Fern
• Red Water Fern
• Fairy Moss
• Mosquito fern
• Water Velvet
• For a list in 26 languages, go here

Accreditation or not

Azollas were identified and named by Philibert Commerçon, an early French naturalist serving under Louis Antoine de Bougainville on his voyage of circumnavigation cira 1766–1769. He was a defender of Taxonomy, an new procedure for naming in science.

Azolla is commonly accepted as a Greek combination of words that translates to “dies in drought”. This makes sense, as it is a water-bound plant.  On the other hand, this is not an ironclad explanation.  Azolla may have been the name from the indigenous peoples of Chile or Argentina. More research is needed to confirm or deny the claim.

Adding to the multilayered history of the plant, Commerçon was probably not its collector. He was often ill with leg ulcers and needed nursing and a collecting assistant.  Enter Commerçon’s housekeeper/nurse Jeanne Baret.  Baret was a peasant, a socially unimportant herb woman. Commerçon would not sail without her help. Baret dressed like a man and pretended to be male to join the voyage. This was illegal in the French navy and risky but her disguise went unchallenged for months. One day they encountered Tahitians who recognized her as Māhū [a two-spirit] and her cover was offically blown. Nevertheless she persevered. She did her employer’s collecting, wrote his notes, ensured his health, and became the first [known] woman to travel around the world.

In the Pink

Water ferns turn pink in cold weather due to an interesting relationship with the cyanobacteria living with it.

Cyanobacteria is an ancient phylum and an aeroplankton, or a plankton capable of traveling through the air for long distances.  It colonizes on many different plants, including our corn and wheat. Once colonized, it absorbs sunlight and expels oxygen, a process called oxygenic photosynthesis.  Cyanobacteria is believed the first organism on Earth to produce oxygen—a lineage that dates back to the Archaeon Eon ~4,000 to 2,500 million years ago. Despite the humble-sounding beginnings, this bacterium is how the Earth shifted from nonbreathable to breathable atmosphere!

Not blue with cold

Regardless of its age, it is still a small, easily-overlooked plant and it takes a lot of them to be noticed by the casual eye.  The public is often confused by “pink scum” in the cold months. Winter is the best time to find Azolla; in warmer weather the green blends in with other floating vascular plants such as duckweeds and it can be difficult to discern. The pink leaves stand out in quiet pools, ponds, and retention areas for freshwater. 

Powerhousing it

Azolla does the hard work of sucking up excess nitrogen from fertilizers and that improves the overall health of the water and surrounding soils. It grows very quickly in ideal conditions, creating thick carpets across the water.  The name “mosquito fern” dates from this function: mosquitoes cannot easily lay their eggs in water covered with the ferns.  It also grows thick enough to stifle algae, though it can harm the ecology if it shades the water for too long. In these modern times, growers simply take a leaf blower and blow the ferns to the edge of the ponds for collection. Ducks and chickens enjoy azolla in their meals, and farmers use it to improve egg production.

Stress makes it blush

Stressors like cold weather ‘bring out the red’ in the ferns.  This makes them easier to find. Unchecked azolla grows until something kills it, or it kills itself.  One solution is simple:  it makes a good rich nitrogenous manure. It has been encouraged to grow in rice paddies and farmlands since the early days of the Fertile Crescent. Thanks to modern technology, the harvesting can be is simple as aiming a leafblower to the carpet and guiding it into nets or on the shore.

Here at the Flett wetlands, the ferns are providing welcome food for the plant-loving birds, most of them migratory.  They float to the top of the forming ice, forming delicate green layers of food.  In milder days their long, drooping roots shelter snails and the larvae of small invertebrates.

Light travels

There are several species in Washington State but A. mexicana is most often found in the CPTC wetlands.  The ‘mexicana’ comes from its native range up the western coast.  Its small, light bodies are easily carried on the feathers and feat of migratory birds. The Flett was for untold generations, a rich hunting ground for ducks and other waterfowl, and to find the two together is but one confirmation of their connections.  Bacteria, plant, birds and the very oxygen of the planet.