Parablechnum is a genus of ferns in the family Blechnaceae (order Polypodiales), placed in the subfamily Blechnoideae by the Pteridophyte Phylogeny Group (PPG I, 2016). The genus was originally described by C.Presl in 1851 and is accepted in the 2016 classification of Blechnaceae by Gasper et al.; some other treatments instead sink it into a broadly circumscribed Blechnum that spans the entire PPG I subfamily Blechnoideae.
Members of Parablechnum are terrestrial or rupestral ferns with short-creeping to suberect rhizomes bearing linear to lanceolate scales. Fronds are dimorphic — sterile fronds typically broader, fertile fronds narrower — and range from small plants of a few decimetres to large, robust specimens exceeding three metres in favourable streamside conditions. The lamina is 1-pinnate with numerous pairs of pinnae; basal pinnae are characteristically shorter than mid-frond pinnae and often carry well-developed sterile auricles at their bases. The rachis and costae frequently bear peltate scales with a distinctive dark "black-spot" centre, a diagnostic feature of several species. Fertile pinnae are narrowly linear, with sori running in a continuous band along the under-surface and covered by a brown, laciniate indusium.
The genus has a predominantly Southern Hemisphere distribution, with species in New Zealand, Australia, South America (including Chile), and adjacent island groups. Parablechnum novae-zelandiae — known by the Māori names kiokio and horokio — is one of the most widespread and recognisable ferns in New Zealand, growing from coastal to montane zones along roadsides, cliff faces, ravines, river banks, and pine plantations. Other members of the genus include Parablechnum wattsii and Parablechnum montanum in Australia, and Parablechnum chilense in South America.
Etymology
The genus name Parablechnum is derived from the Greek para- ("beside" or "near") and Blechnum, the closely related genus to which it was formerly often assigned. The specific epithet of the best-known species, novae-zelandiae, is Latin for "of New Zealand."
Distribution
Parablechnum has a predominantly Southern Hemisphere distribution spanning New Zealand (including the Kermadec Islands, North and South Islands, Stewart Island, and Chatham Islands), Australia, and South America (including Chile and adjacent regions). Within New Zealand, species such as P. novae-zelandiae are found from coastal lowlands to montane elevations, and the genus is among the most ecologically widespread fern groups in that country.
Ecology
Species of Parablechnum inhabit a range of moist environments, including streambanks, ravines, roadsides, cliff faces, and forest understories. Parablechnum novae-zelandiae has a wetland indicator status of FAC (facultative), meaning it occurs commonly in both wetland and non-wetland settings. It is notably adaptable, colonising disturbed habitats such as pine plantations and urban roadsides in New Zealand.
Taxonomy Notes
Parablechnum was described by C.Presl in 1851 but was long treated as part of Blechnum. Its reinstatement as a distinct genus follows the 2016 molecular phylogenetic classification of Blechnaceae by Gasper et al., which was adopted by PPG I (2016). Some authorities continue to treat Parablechnum within a broadly defined Blechnum that encompasses the entire PPG I subfamily Blechnoideae. The genus currently encompasses approximately 76 species and one hybrid under PPG I, though GBIF backbone counts vary by checklist.
Propagation
Parablechnum novae-zelandiae is easily grown from fresh spores and transplants well, flourishing in most conditions. Plants need sufficient space to spread as they can self-establish freely and occasionally become aggressive in small garden settings.
