Azolla filiculoides

Common Name: water fern 
Type: Fern
Family: Salviniaceae
Native Range: Argentina, Brazil, Uruguay, Peru
Zone: 7 to 10
Height: 0.25 to 0.25 feet
Spread: 1.00 to 3.00 feet
Bloom Time: Non-flowering
Bloom Description: Non-flowering
Sun: Full sun to part shade
Water: Wet
Maintenance: High
Suggested Use: Annual, Water Plant, Naturalize, Rain Garden
Leaf: Colorful
Tolerate: Rabbit


Grow on still water in full sun to part shade. Scatter small bunches of plants on the water surface after last frost date. Spreads quickly in optimum conditions. Net out excess plants as needed. Can spread rapidly in frost-free climates. In the wild, it survives winter in cold weather climates by way of overwintering bodies that sink to the bottom in fall and rise to the surface in spring only after temperatures have warmed up. This phenomenon is usually not seen in home water gardens in the St. Louis area where it is recommended that some plants be lifted each year in fall before first frost and overwintered in a saucer of moist soil in a bright frost-free area or in an aquarium.

Noteworthy Characteristics

Azolla filiculoides, commonly called mosquito fern, is a deciduous, free-floating, aquatic perennial fern that forms rapidly expanding, moss-like mats of foliage (to 1/2” tall) on still water surfaces. In optimum conditions, the foliage becomes so dense as to reportedly prevent mosquito larva from developing and hatching, hence the common name. It is a popular addition to water gardens and ponds, where it not only provides attractive foliage cover but also discourages algae growth and helps keep waters clear. Foliage is bright green in shade, but develops attractive purplish-rose tints in full sun. All plants turn reddish-purple in fall as temperatures cool. Pinnately branched stems are densely clad with minute, often overlapped, two-lobed leaves (1/4” long) in two rows. Tiny roots trail downward from the lower surfaces of the stem forks. This fern is native to lakes, ponds, streams and rivers in both North and South America.

Genus name comes from the Greek words azomeaning to dry and olluo meaning to kill. The plants will easily die when they become too dry.

Specific epithet means resembling fern.


No serious insect or disease problems.


Free floating aquatic perennial for water gardens or ponds.