Forest & Kim Starr
Plant Common Name
It's hard to believe the species in family of aquatic, floating plants are in fact miniscule ferns. There are approximately 13 species of Azolla, which can be found across the Northern Hemisphere. They are free-floating plants that exist atop the water's surface and all are very tiny. If fact, they are the smallest of the ferns. They tend to be feather-like and may be adapted to fresh or brackish water.
These little ferns thrive in pools with full or partial sun. If you wish to add Azolla to water gardens or aquatic containers, be sure to choose species native to North America. These include Azolla caroliniana for the east and Azolla filiculoides or Azolla mexicana for the west and southwest. The introduced species, Azolla pinnata, is considered a noxious water weed in North Carolina, so gardeners should refrain from planting it to avoid further spread and problems.
One unique trait of Azolla is their ability to fix atmospheric nitrogen into a usable form. They do this via a symbiosis with the cyanobacterium, Anabaena azollae. Nitrogen is one of the three vital macronutrients needed for plant health, so Azolla species have also been used as biofertilizers.
Bark or Stem Fragrant