Blechnum is a genus of ferns. Two very different circumscriptions of the genus are used by different authors. In the Pteridophyte Phylogeny Group classification of 2016 (PPG I), Blechnum is one of 18 genera in the subfamily Blechnoideae of the family Blechnaceae, and has about 30 species. Other sources place many more species in the genus, with only two other genera in the subfamily. The genus then has about 250 species.
Species placed in Blechnum by Plants of the World Online, which uses the broad circumscription, but transferred to other genera by the Checklist of Ferns and Lycophytes of the World, which uses the narrow circumscription, are listed below together with their alternative placement.
A
Blechnum acanthopodum T.C.Chambers & P.A.Farrant = Parablechnum acanthopodum (T.C.Chambers & P.A.Farrant) Gasper & Salino Blechnum acutum (Desv.) Mett. = Lomaridium acutum (Desv.) Gasper & V.A.O.Dittrich Blechnum aequatoriense A.Rojas = Austroblechnum aequatoriense (A.Rojas) Gasper & V.A.O.Dittrich Blechnum × aggregatum (Colenso) Tindale = Austroblechnum × aggregatum (Colenso) Gasper & V.A.O.Dittrich Blechnum amabile Makino = Struthiopteris amabilis (Makino) Ching Blechnum ambiguum C.Presl = Parablechnum ambiguum (Kaulf. ex C.Presl) C.Presl Blechnum andinum C.Chr. = Austroblechnum andinum (Baker) Gasper & V.A.O.Dittrich Blechnum articulatum (F.Muell.) S.B.Andrews = Parablechnum articulatum (F.Muell.) Gasper & Salino Blechnum ascendens A.Rojas = Austroblechnum ascendens (A.Rojas) Gasper & V.A.O.Dittrich Blechnum asperum (Klotzsch) J.W.Sturm = Austroblechnum asperum (Klotzsch) Gasper & V.A.O.Dittrich Blechnum atropurpureum A.R.Sm. = Parablechnum atropurpureum (A.R.Sm.) Gasper & Salino Blechnum attenuatum (Sw.) Mett. = Lomaridium attenuatum (Sw.) Gasper & V.A.O.Dittrich Blechnum auratum (Fée) R.M.Tryon & Stolze = Lomariocycas aurata (Fée) Gasper & A.R.Sm. Blechnum austrocaledonicum Christenh. = Doodia gracilis Copel.
B
Blechnum bakeri C.Chr. = Cranfillia bakeri (C.Chr.) Vázquez Ferreira & Molino S. Blechnum banksii (Hook.f.) Mett. = Austroblechnum banksii (Hook. fil.) Gasper & V.A.O.Dittrich Blechnum bicolor M.Kessler & A.R.Sm. = Parablechnum bicolor (M.Kessler & A.R.Sm.) Gasper & Salino Blechnum biforme (Baker) Christ = Lomaridium biforme (Baker) Gasper & V.A.O.Dittrich Blechnum binervatum (Poir.) C.V.Morton & Lellinger = Lomaridium binervatum (Poir.) Gasper & V.A.O.Dittrich Blechnum binerve (Hook.) C.Chr. = Lomaridium xiphophyllum (Baker) Gasper & V.A.O.Dittrich Blechnum bolivianum M.Kessler & A.R.Sm. = Parablechnum bolivianum (M.Kessler & A.R.Sm.) Gasper & Salino Blechnum bonapartei Rakotondr. = Lomaridium bonapartei (Rakotondr.) Gasper & V.A.O.Dittrich Blechnum brackenridgei (Carruth.) Perrie & Brownsey = Doodia brackenridgei Carruth. Blechnum brasiliense Desv. = Neoblechnum brasiliense (Desv.) Gasper & V.A.O.Dittrich Blechnum bruneum M.Kessler & A.R.Sm. = Lomaria brunea (M.Kessler & A.R.Sm.) Gasper & V.A.O.Dittrich
C
Blechnum camfieldii Tindale = Parablechnum camfieldii (Tindale) Gasper & Salino
Blechnum capense Burm.f. = Parablechnum capense (Burm. fil.) Gasper & Salino
Blechnum cartilagineum Sw. = Oceaniopteris cartilaginea (Sw.) Gasper & Salino
Blechnum castaneum (Makino) Makino & Nemoto = Struthiopteris castanea (Makino) Nakai Blechnum chambersii Tindale = Austroblechnum lanceolatum (R.Br.) Gasper & V.A.O.Dittrich Blechnum chauliodontum Copel. = Parablechnum chauliodontum (Copel.) Gasper & Salino Blechnum chiriquanum (Broadh.) C.Chr. = Parablechnum chiriquanum (Broadh.) Gasper & Salino Blechnum christii C.Chr. = Parablechnum christii (C.Chr.) Gasper & Salino Blechnum cochabambense M.Kessler & A.R.Sm. = Parablechnum cochabambense (M.Kessler & A.R.Sm.) Gasper & Salino Blechnum colensoi (Hook.f.) N.A.Wakef. = Austroblechnum colensoi (Hook. fil.) Gasper & V.A.O.Dittrich Blechnum columbiense Hieron. = Lomariocycas columbiensis (Hieron.) Gasper & A.R.Sm. Blechnum confusum (Fourn.) Brownlie = Parablechnum confusum (E.Fourn.) Gasper & Salino Blechnum contiguum Mett. = Lomaridium contiguum (Mett.) Gasper & V.A.O.Dittrich Blechnum corbassonii Brownlie = Parablechnum corbassonii (Brownlie) Gasper & Salino Blechnum cordatum (Desv.) Hieron. = Parablechnum cordatum (Desv.) Gasper & Salino Blechnum corralense Espinosa = Austroblechnum corralense (Espinosa) Gasper & V.A.O.Dittrich Blechnum cyatheoides (Kaulf.) Christenh. = Sadleria cyatheoides Kaulf. Blechnum cycadifolium (Colla) J.W.Sturm = Lomariocycas cycadifolia (Colla) Gasper & A.R.Sm.