Azolla is sometimes called duckweed fern, water fern, fairy moss and /or mosquito fern but the real name comes from the Greek azo meaning “to dry” and ollo meaning “to kill” (by drought) or “killed by drought.”
Do not confuse this with the native duckweed
But that’s not a very nice name even though it does describe the plant quite nicely.
This oxygenator will float nicely all summer and then in warmer zones, it produces a fruiting body and sinks to the bottom of the pond where it will overwinter.
In colder regions, it simply dies. In the heat of the summer, it reproduces very quickly and can quickly blanket a small pond.
I would caution against introducing it to larger ponds unless you have long handled nets to scoop it out. It is one of the most aggressive plants in the pond
Fish fry and microorganisms thrive in the shelter it provides so it does have a role in the garden.
Most fish will not eat this plant so it does provide shade and algae control in the small pond.
A handful in the spring will go a long way if you have to purchase it. I used to give it away as a weed when I had my nursery but a few bucks will buy you all you need. It does make an excellent addition to the compost pile when you get too much of it.