Fairy moss, also called water fern is not moss but a free-floating aquatic fern. It is a popular addition to water gardens of any size, valued for its soft, delicate look and for its dense growth, which forms a thick mat that blocks out light below and helps to reduce algae growth. It provides a habitat and food for fish—koi and goldfish like to nibble on the fairy weed fronds. The plant grows into such an impenetrable barrier that it is said to prevent mosquitoes from laying their eggs, hence its other name, mosquito fern. Fairy moss is a perennial in warm climates and is grown as an annual in cooler climates. In the fall, the deciduous foliage turns reddish-purple.

Where to Plant Fairy Moss 

Fairy moss needs a body of still water such as a garden pond that is at least 5 to 6 inches deep. It won’t grow well in water bodies with strong currents as its tender fronds get damaged. As a floating fern, its roots grow under water and the foliage is on the surface. The plant should not be fully submerged. The location can be in full sun or partial shade. The water should not have high salt content and be slightly acidic, neutral, or alkaline.

Because fairy moss forms a thick carpet, interplanting it with other non-submerged aquatic plants is not ideal. It is suitable as an underplanting beneath taller water-garden favorites.

How and When to Plant Fairy Moss

After the last spring frost when daytime temperatures are consistently above 59 degrees F, scatter small bunches of plants on the water surface. In the right water and light conditions and in warm weather, fairy moss will spread quickly. The only thing you need to do after planting is to monitor the water quality and remove excess growth.

Fairy Moss Care Tips

Fairy moss is an easy plant to grow but it is high maintenance because of its rapid growth, which needs to be kept in check. 

Light

Fairy moss grows fastest in full sun (at least 6 to 8 hours of direct light per day), but it also grows in locations with partial sun, preferably in the morning. The less sun it gets, the slower fairy moss grows, which means it is less efficient at blocking algae and slower to improve water quality. The light exposure also has an impact on the foliage color. It is bright green in shade and has attractive purplish-rose tints in full sun. 

Soil and Water

For this aquatic plant, monitoring the water quality is key. Fairy moss needs a pH between 4.5 and 7 and won’t do well if the water is too acidic or too alkaline. Regularly testing the water is also necessary to determine whether it needs nutrient supplements. 

Temperature and Humidity

The ideal temperature range for fairy moss is between 68 to 82 degrees F. In warm climates where fairy moss is reliably hardy, you can leave it outdoors in your water gardens year-round. In colder areas, it's best to treat it as an annual and only keep it in your pond during the spring and summer.

Fairy moss needs high relative humidity of 80 to 90%; it won’t do well in a dry environment. 

Fertilizer

The most important main nutrient for fairy moss and the one that it is most likely lacking is phosphate. but don’t add it to your pond water without testing the water beforehand. Phosphate can enter water through many different sources, including fish food, and an excessive level of phosphate is detrimental to plant and aquatic life. 

Pruning

This is a plant that can double in size within days. Keeping a close eye on its growth and removing excess—in warm weather, this might be necessary on a daily basis—is crucial. If it’s not controlled, it becomes invasive, deprives submerged aquatic plants of light, and clogs up filtration systems. 

Potting and Repotting Fairy Moss

As a free-floating aquatic plant, fairy moss is not suitable to be grown in pots. 

Pests and Problems

The plant is free of serious pests and diseases and tolerant of rabbits. 

How to Propagate Fairy Moss

Thanks to its vigorous and fast growth, fairy moss is easy to propagate from division. Do this in warm weather when the plant is actively growing. Take a section of an existing plant and place it in a new area with suitable growing conditions. 

Types of Fairy Moss 

Eastern Mosquito Fern

Azolla caroliniana, also known as Carolina mosquito fern, is an annual native aquatic fern less than 1 inch tall. 

Mexican Mosquito Fern

Azolla mexicana is an aquatic fern native to Mexico, British Columbia, and the western United States. It often forms multi-layered floating mats. When young, the foliage is bright green to blue-green and often turns dark red or pinkish later in the season. It is an annual or short-lived perennial.

Fairy Moss Companion Plants

Canna

Bold cannas are perfect for moist locations and full sun. In their native habitats, cannas are often seen growing close to and even in the water, which makes them ideal candidates for landscaping around a pond. Zone 7-10

Papyrus

Papyrus is an easy-to-grow water plant. It sends out grassy sprays of leaves that jut out from the stems like a fireworks display. The moist soil at the edge of a body of water is a perfect location for papyrus. Many common water garden plants are relatively low growing, so papyrus makes a dramatic focal point—both for its height and texture. Zone 9-10

Swamp Lily

These native lilies send out fragrant spidery flowers in shades of white, pink, and red in early summer. Flower stalks emerge above 2 to 5-foot-tall arching straplike green leaves. They bloom best in moist soil at the edge of a pond. Zone 8-11