Azolla microphylla
Mexican waterfern fern, mosquito fern

Distribution: Occurring on both sides of the Cascades crest in Washington; British Columbia to California, east to Texas.

Habitat: Ponds and backwaters, mostly at low elevations.

Origin: Native

Growth Duration: Annual, Perennial

Conservation Status: Not of concern


Floating aquatic perennials, sometimes forming floating mats of multiple layers, green or commonly blueish green or pinkish to dark red; stems prostrate and 1-1.5 cm, lacking hairs; roots 3-5 cm.


Leaves sessile, and alternate, overlapping, 0.6-2 mm broad, 2-lobed; largest hairs on upper leaf lobe near stem, 2-3-celled; broad pedicel cell usually 1/2 or more of height of hair with curved apical cell with tip nearly parallel to leaf surface.


Sporocarps in pairs at base of lateral branches, megasporocarps each containing 1 megasporangium that produces 1 spheric megaspore 0.2-0.6 mm, pitted and sparsely covered with few long 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 microphylla Kaulf.
Publication: Enum. Filic. 273. 1824.

Synonyms & Misapplications:
Azolla mexicana Schltdl. & Cham. ex Kunze [FNA2, HC]
Additional Resources:

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

WA Flora Checklist: Azolla microphylla checklist entry

OregonFlora: Azolla microphylla information

E-Flora BC: Azolla microphylla atlas page

CalPhotos: Azolla microphylla photos

15 photographs:
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