How to Grow Red Mosquito Fern
iNaturalist
Red Mosquito Fern
Azolla filiculoides
fernAzolla filiculoides is a small, floating aquatic fern native to tropical and subtropical Americas that forms dense mats on water surfaces. It rapidly multiplies and changes color from green to reddish-brown depending on light and nutrient conditions. This fern is valued as a nitrogen-fixing biofertilizer, livestock feed, and natural water purifier.
When should you plant Red Mosquito Fern in your zone?
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Example Red Mosquito Fern timeline · Pittsburgh, PA (Zone 6b)
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Plant Red Mosquito Fern
Around Apr 17Near Pittsburgh's average last spring frost.
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Tend & protect
Late spring–summerWatering, feeding, and pest-watch reminders.
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Harvest Red Mosquito Fern
Around Apr 27≈ 10 days after planting
Sample dates for Pittsburgh, PA. Sign up to get exact Red Mosquito Fern dates for your own zip code.
Growing Conditions
Soil
Growing Zones
Find your zone →Thrives in warm zones 9-11; can be grown seasonally or indoors in cooler climates
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Establishment
1-2 weeksTiny individual fronds begin to multiply and establish a small mat on the water surface
Start with high-quality stock; ensure warm water (above 68°F) and gentle water conditions; avoid strong currents
Vegetative Growth
2-4 weeksFronds multiply rapidly, forming increasingly dense mats; color remains bright green with good nutrient availability
Monitor water temperature and nutrient levels; thin mats as needed to prevent total coverage; provide consistent full sun for faster growth
Maturation & Color Development
3-6 weeksMat thickens; fronds may develop reddish or brownish tones in response to high light or phosphorus stress
Increase light exposure to encourage red pigmentation; reduce nitrogen slightly if desired; maintain water temperature above 70°F
Sporulation (Optional)
Variable; occurs when growth conditions become limitingUnder stress or as part of sexual reproduction, sporocarps develop; fern produces spores that remain dormant until conditions improve
If spore dormancy is desired (for storage/preservation), allow partial drying and cool storage; sporulation is uncommon in continuous warm, well-fed conditions
Companion Planting
Plan your garden →Plant with:
Avoid planting near:
Common Pests
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Increase water circulation; remove heavily infested mats; predatory insects and fish provide biological control
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Introduce mosquito fish (Gambusia) or dragonfly nymphs; maintain water movement; ensure mats don't create completely still zones
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Improve water aeration and circulation; remove dead or rotting biomass promptly; maintain optimal pH (6-7) and temperature
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Remove affected portions; ensure adequate dissolved oxygen; avoid water stagnation and organic overload
Uses
Livestock & Aquaculture Feed
CulinaryAzolla is a nutritious, high-protein feed supplement for ducks, chickens, tilapia, and other farmed animals. Its rapid growth makes it a sustainable, cost-effective protein source in tropical agriculture. [source]
Traditional Herbal Medicine
MedicinalIn Southeast Asian traditional medicine, Azolla is used to treat wounds, reduce inflammation, and support general wellness. Contains vitamins, minerals, and bioactive compounds. [source]
Nitrogen-Fixing Biofertilizer
HouseholdAzolla hosts symbiotic cyanobacteria (Anabaena) that fix atmospheric nitrogen, making it an excellent organic fertilizer for rice paddies and crops. Improves soil fertility without synthetic inputs. [source]
Water Purification & Bioremediator
HouseholdAzolla absorbs excess nutrients and pollutants from water, reducing algae blooms and improving water quality. Used in wastewater treatment and pond management. [source]
Ecosystem Support & Habitat
WildlifeDense Azolla mats provide shelter and breeding habitat for aquatic insects, fish, and microorganisms. Increases biodiversity in ponds and wetlands while producing oxygen. [source]
This is not medical advice. LizPlants is not a medical resource. Always consult a qualified healthcare professional before using plants medicinally.
Harvest Tips
Azolla can be harvested continuously once established. Use a net or scoop to remove 25-50% of the mat weekly. Harvest in early morning or late afternoon. Rinse harvested material lightly if intended for livestock feed or soil amendment. For best nutritional content as animal feed, harvest before excessive senescence. Can be dried for storage (lay flat in sun for 3-5 days) or used fresh immediately.
Fun Facts
- 🌱 Azolla filiculoides doubles its biomass every 3-5 days under ideal conditions, making it one of the fastest-growing plants on Earth—potentially producing 20 tons of dry matter per hectare annually.
- 🌱 The fern's symbiotic relationship with the cyanobacterium Anabaena azollae allows it to fix atmospheric nitrogen without any fertilizer input, historically used to increase rice yields in Asia for over 1,000 years.
- 🌱 Azolla changes color from bright green to deep red or burgundy under nutrient stress or intense sunlight, a natural stress response that serves as a visual indicator of water and nutrient conditions.
Gardening Terms
New to gardening? Learn about terms used in this guide:
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