Sword or Fishbone Fern (Nephrolepis cordifolia), a pan-tropical fern that was likely indigenous to parts of NSW and Queensland, and has been introduced to other areas of the country as a consequence of its widespread cultivation as an ornamental.
Parts of its pan-tropical distribution, including its presence in Hawaii and the Americas, may also be a consequence of human intervention in the late 19 and early 20th c. Populations in Victoria are likely to represent overseas genetic material, although some commercial cultivars may have been sourced from the presumed native populations in QLD/NSW. The species has been available from Melbourne nurseries since the 1880s.
Sword Fern has shown up on species lists for Melbourne’s southeast since the 1980s. In 2006, it was recorded at the Tooranga, Gardiner, East Malvern and Darling Railway Stations, growing variously on station building and platform walls, often with Tender Brake (P. tremula) or Sword Brake (P. multifida). Described as an ‘occasional garden escape’ in Flora of Victoria and Flora of Australia, the additional structural instances shown here are suggestive that, while uncommon, the species is certainly able to spread its spores to new locations in the metropolitan environment and is, again, likely under-recorded.
The plants shown are present on structures of bluestone, clay masonry and/or concrete in the Melbourne CBD, at Northcote and at Kororoit Creek in Brooklyn. In all cases, the colonised structure is posited to receive dependable moisture via seeping ingress from adjacent sources — from roadway sub-bases and leaky pipes in the Melbourne and Northcote examples, and from the former Main Outfall Sewer (a disused brick channel that collects and retains water) at Brooklyn.
In the CBD example, there was an observable dry-weather seep through the bluestone wall some metres below the Nephrolepis colony. This seep, and other positions on the wall, are colonised by Tender Brake, and indeed on all three structures Brakes (Pteris multifida, P. tremula and/or P. vittata) occupied adjacent niches.