Adiantum trapeziforme

Diamond maidenhair
Conservation status
Vulnerable  (NatureServe)
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Division:	Polypodiophyta
Class:	Polypodiopsida
Order:	Polypodiales
Family:	Pteridaceae
Genus:	Adiantum
Species:	A. trapeziforme
Binomial name
Adiantum trapeziforme L.
Synonyms
see text

Adiantum trapeziforme, the giant maidenhair or diamond maidenhair, is a species of fern in the genus Adiantum , native to the tropical rainforests of Central and South America.

Description

Maidenhair ferns, genus Adiantum, grow on the ground and on rocks. Species in the genus are mainly identified by this feature: ^{[1] [2]}

Adiantum trapeziforme false indusia on pinnule undersides

• The spore-producing sporangia are produced along one side of the smallest division of a compound leaf, the "pinnule," in structures consisting of turned-under flaps of the pinnule's margin, known as "false indusia"; the false indusia are separated from one another as shown at the left.

Among the 245 or so accepted Adiantum species ^[3] , Adiantum trapeziforme is further distinguished by these features: ^[4]

• Blades are 2-4 times pinnately divided.
• The final segments, the pinnules, are relatively large, up to 5cm long and 2cm across (~2 x +3⁄4 inches).
• The pinnules usually have a trapeziform shape.
• Blade stipes are dark purple to blackish and lustrous, of nearly half the blade's length and hairless; where the stipe extends into the blade as the rachis, it's dark purple.

Distribution

Adiantum trapeziforme is native to parts of Mexico, Cuba, Jamaica, the Lesser Antilles south through Central America, Trinidad and possibly Venezuela. ^[5] It is documented, apparently introduced, in India, Sri Lanka and the US state of Florida ^[6] . Citizen scientists contributing to iNaturalist appear to have observed the species in other locations as well, particularly in Indonesia and Oceania. ^[7]

Habitat

Adiantum trapeziforme occurs in wet forests and secondary forests, from lower elevations to 1000 meters (~3300 feet). ^[5]

Traditional uses

Adiantum trapeziforme has been documented used to treat snakebite and to help girls from being bothered when walking along the road. ^[8] Also, the fronds are used as decorations. ^[9]

Taxonomy

Within the family Pteridaceae, Adiantum trapeziforme belongs to the subfamily Adiantoideae. ^[10]

The species Adiantum trapeziforme has been known by these synonyms: ^[11]

• Adiantum cultratum J.Sm. ex Hook. (1851), nom. illeg.
• Adiantum eminens C.Presl (1836)
• Adiantum formosissimum Klotzsch (1844)
• Adiantum rhomboideum Schkuhr (1809)
• Adiantum schmalzii Rosenst. (1910)
• Adiantum trapeziforme var. cultratum Baker(1867)
• Adiantum trapeziforme var. oblongatum (1857)
• Adiantum trapeziforme var. plumieri T.Moore (1857)

Etymology

The genus name Adiantum derives from the Greek adiantos, meaning "unwetted," in reference to the hairless leaves which shed raindrops. ^[1]

The species name trapeziforme is assumed to be New Latin construct based on the Latin trapezium, used to name any four-sided form in which no side is parallel to another, and iformis, meaning "-iform", or "formed like." ^[12]

Gallery

• 
  Adiantum trapeziforme pinnule size compared to a hand
• 
  Adiantum trapeziforme compound leaf
• 
  Adiantum trapeziforme

References

1. Paris, Cathy A. "1. Adiantum Linnaeus, Sp. Pl. 2: 1094. 1753; Gen. Pl. ed 5, 485. 1754". efloras.org. Flora of North America. Retrieved January 15, 2026.
2. "Adiantum". SEINet Arizona-New Mexico Chapter. SEINet Portal Network. Retrieved January 15, 2026.
3. "Adiantum L." Plants of the World Online. United Kingdom: Royal Botanic Gardens Kew. Retrieved January 15, 2026.
4. "Adiantum trapeziforme L." World Flora Online. WFO (2026) on the Internet. Retrieved January 15, 2026.
5. Prado, Jefferson; Palacios-Rios, Mónica (1998). "Taxonomy and Distribution of Adiantum trapeziforme and A. pentadactylon". American Fern Journal. 88 (4). American Fern Society: 145–149. Bibcode:1998AmFJ...88..145P. doi:10.2307/1547765. JSTOR   1547765 . Retrieved January 15, 2026.
6. "Adiantum trapeziforme (ADITR)". EPPO Global Database. Secretariat of the European and Mediterranean Plant Protection Organization (EPPO). Retrieved January 15, 2026.
7. "Diamond Maidenhair Fern (Adiantum trapeziforme)". inaturalist.org. iNaturalist. Retrieved January 15, 2026.
8. Palacios Rios, Mónica (1992). Las Pteridofitas del Estado de Veracruz, México (PDF) (Maestra en Ciencias (Biología) thesis) (in Spanish). Mexico City, México: Universidad Nacional Autónoma de México. Retrieved January 15, 2026.
9. Santos-Chacón, William (July–December 2010). "Fitorrecursos en la Reserva Ecológica "El Gigante"". Revista Forestal Baracoa (in Spanish). 29 (2). La Soledad, Guisa, Granma. Cuba: Estación Experimental Forestal Guisa: 104–112. ISSN   0138-6441 . Retrieved January 15, 2026.
10. "Adiantum trapeziforme L." catalogueoflife.org. Catalogue of Life. December 20, 2025. Retrieved January 15, 2026.
11. "Adiantum trapeziforme L." Plants of the World Online. United Kingdom: Royal Botanic Garden Kew. Retrieved January 15, 2026.
12. "trapezium noun". merriam-webster.com. Merriam-Webster. Retrieved January 15, 2026.