Azolla is a small free-floating fern approximately 1 to 3/8 inches wide. Leaves of the mosquito fern overlap, giving a quilted look to the surface and hiding the stem. A single root protrudes from each stem. Azolla can vary in color from green to red and are generally found in quiet ponds protected from wind action. Azolla can be aggressive invaders in quiet ponds and are often found mixed in with duckweed or watermeal.
Other Names: Fairy moss, mosquito fern, water fern, duckweed fern, or Carolina fern
Broad spectrum contact herbicides, such as Ultra PondWeed Defense®, will quickly kill Azolla. Because it does not stay in the water body, multiple treatments may be needed throughout the season.
Chemical Application Best Practices
Anytime you use chemicals treat weeds or algae, please keep in mind the following:
- Treat your pond in sections. Treat only half the pond's surface at a time. During hot weather or when treating heavy growth, it is important to treat no more than ¼ of your pond at a time and wait the full 14 days before re-applying. This helps lower the risk of fish loss during hot weather or when treating heavy growth.
- Once the weeds have browned, use a rake to remove as much dead material as possible. This prevents an accumulation of dead plant material and muck.
- Take a proactive approach to pond management. Use PondClear™, MuckAway™ and Pond Dye to keep your pond looking great. For more information, see our article on the Airmax® Ecosystem™
Ask an Expert
If you are unable to identify your pond weed(s) using our Weed ID Guide, follow this article to email us a photo.