Azolla pinnata R.Br.




Azolla pinnata R.Br., Prodr. Fl. Nov. Holl.: 167. 1810; Holttum, Rev. Fl. Malaya ed. 1, 2: 622. 1955 [‘1954’]; Holttum, Dansk Bot. Ark. 20: 35. 1961; Tagawa & K.Iwats., SouthE. Asian Stud. 5: 113. 1967; Tagawa & K.Iwats., Fl. Thailand 3: 605, f. 60.9. 1989; Saunders & Fowler, Bot. J. Linn. Soc. 109: 348. 1992; Saunders, Fl. Males., Ser. II, Ferns and Fern Allies 3: 282. 1998; Boonkerd & Pollawatn, Pterid. Thailand: 98, 116. 2000. – Type: R.Brown 134, Oct. 1804, Australia, Richmond, Hawkesbury (lecto BM; isolecto E, K).

Salvinia imbricata Roxb. ex Griff., Calcutta J. Nat. Hist. 4: 470. 1844. – Azolla pinnata var. imbricata (Roxb. ex Griff.) Bonap., Notes Ptérid. 7: 130. 1918. –Azolla imbricata (Roxb. ex Griff.) Nakai, Bot. Mag. (Tokyo) 39: 185. 1925; Dy Phon, Dictionary of Plants used in Cambodia: 56. 2000.


Floating aquatic. Rhizome short creeping, branching alternately, with many submerged roots, hairy. Roots up to 5 cm long, bearing root-hairs. Stems densely pinnate, forming triangular outline for the whole plant, 1–3 cm long. Fronds bilobed. Leaves less than 1 mm long, purplish to reddish when old; upper surface densely papillose, with semi-transparent cartilaginous membrane at margin. Sori near the base of submerged lobes, enclosed by indusia; a megasporangium or numerous microsporangia in each sori.

Distribution in Thailand

NORTHERN: Chiang Mai, Kamphaeng Phet; CENTRAL: Phra Nakhon Si Ayutthaya; SOUTH-EASTERN: Chanthaburi; PENINSULAR: Surat Thani.

Wider Distribution



Floating on canals or on paddy fields usually in sunny places at low altitudes.

IUCN Conservation Assessment

Least Concern (LC) as listed on the IUCN Red List at http://www.iucnredlist. org/apps/redlist/details/168790/0.


According to Saunders & Fowler (1992) Azolla pinnata has three subspecies of which the subspecies in Southeast Asia is Azolla pinnata subsp. asiatica Saunders & Fowler.  It is used as a green manure.

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