Azolla filiculoides
duckweed fern, large mosquito fern

Distribution: Occurring on both sides of the Cascades in Washington; British Columbia to California, east to Idaho and western Montana.

Habitat: Ponds, backwaters, slow-moving streams.

Origin: Native

Conservation Status: Not of concern


Floating aquatic perennials, green to yellow-green to dark red, with 2 growth stages and only fertile in mature stage; stems prostrate and 1-3 cm when immature, nearly erect and 3-5 cm at maturity when crowded, lacking hairs; roots 3-5 cm.


Leaves sessile, and alternate, overlapping, 0.6-2 mm broad, 2-lobed, with 1-celled hairs on adaxial surface of upper lobe; emersed lobe greenish to reddish with narrow colorless margin, immersed lobe slightly larger than emersed lobe and often lacking color.


Sporocarps in pairs at base of lateral branches, megasporocarps each containing 1 megasporangium that produces 1 spheric megaspore 0.2-0.6 mm with a warty surface and tangled filaments; microsporocarps globose, apex with a rounded protuberance, 10-27 micrometers in diameter, containing up to 130 microsporangia, microsporangia each containing 32 or 64 microspores 3 micrometers in diameter.

Accepted Name:
Azolla filiculoides Lam.
Publication: Encycl. 1: 343. 1783.

Synonyms & Misapplications:
(none provided)
Additional Resources:

PNW Herbaria: Specimen records of Azolla filiculoides in the Consortium of Pacific Northwest Herbaria database.

WA Flora Checklist: Azolla filiculoides checklist entry.

E-Flora BC: Azolla filiculoides atlas page.

CalPhotos: Azolla filiculoides photos.

USDA Plants: Azolla filiculoides information.

16 photographs:
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