Water Fern (Azolla filiculoides) is a deciduous, free-floating aquatic fern that transforms still water surfaces into delicate, moss-like mats of foliage rarely exceeding half an inch tall. Hardy in zones 7-10, this perennial thrives in full sun to partial shade and spreads with remarkable speed under optimal conditions, creating living carpets that suppress algae and reportedly prevent mosquito larvae from developing. Its rapid growth and low profile make it a dynamic addition to water gardens and ponds, where it serves as both ornamental cover and functional ecological tool.
Partial Sun
Moderate
7-10
3in H x 36in W
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High
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Water Fern earns its common name mosquito fern from its documented ability to prevent mosquito larvae from hatching in dense mats, a natural pest management benefit rarely found in ornamental aquatics. The foliage shifts color with seasons and conditions, creating visual interest throughout the growing months. It survives winters in cold climates through a fascinating process: in fall, specialized overwintering bodies sink to the pond bottom, then rise back to the surface in spring once temperatures warm. This ancient survival mechanism means you can enjoy year-round interest even in temperate regions, and the plant requires no special winter care if your pond doesn't freeze solid.
Water Fern is cultivated primarily as a living ornament for water gardens and ponds, where it serves multiple functions simultaneously. The dense mats provide surface cover that enhances water aesthetics while reducing algae growth through shading. As an edible plant, it can be harvested and consumed, though its primary value in home gardening lies in its ecological benefits and visual interest rather than culinary use. It is also valued in rain gardens and as a naturalized water plant that establishes itself quickly without requiring intensive intervention once established.
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After your last frost date, scatter small bunches of Water Fern plants directly onto still water surfaces where they will float and establish themselves. Choose locations with full sun to partial shade exposure. The plants will root themselves to the water column and begin spreading within days under favorable conditions.
Water Fern can be harvested by hand or net as the plant is edible, though harvest timing is flexible since the entire mat is consumable at any point during the growing season from April through September. Simply remove desired portions of the floating mat from the water surface.
Remove excess growth by netting out unwanted plants from the water surface as needed throughout the growing season. In frost-free climates, frequent removal keeps the fern in check; in colder zones, growth naturally slows in late summer and fall.
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