Fishbone fern

Nephrolepis cordifolia
Herb
Alternate
Compound
No colour
Green

a fern with upright or drooping fronds usually up to 50 cm long.

this species often produces distinctive round tubers on its creeping underground stems.

its 'leaves' are divided into numerous alternatively arranged narrow 'leaflets' (10-35 mm long and 4-11 mm wide).

the lower parts of the 'leaflets' are usually somewhat overlapped and slightly lobed on one side, while their tips are relatively broad and somewhat rounded.

its brown spores are produced is small clusters midway between the centre and the margin of the undersides of the 'leaflets'.

Common names 
Also known as: erect sword fern, herringbone fern, ladder fern, narrow swordfern, southern sword fern, sword fern, tuber fern, tuberous sword fern,
Family 
Nephrolepidaceae
Deciduous 
No
Flowering time 
N/A
Native/Exotic 
Native
Origin 
It is thought to be native to many tropical regions of the world (i.e. pan-tropical), including some parts of northern Australia (i.e. the coastal districts of eastern Queensland and some parts of north-eastern New South Wales).
Notifiable 
No
State declaration 
Nil
Council declaration 
Class R – Reduce populations
Known distribution 

Naturalised in Victoria, in the coastal districts of south-western Western Australia, on Norfolk Island and beyond its native range in the coastal districts of central New South Wales. Possibly also naturalised on Lord Howe Island and regarded as being naturalised in some habitats and areas that are outside its natural distribution in south-eastern Queensland and north-eastern New South Wales.

Widely naturalised overseas in Africa, temperate Asia, New Zealand and south-eastern USA (i.e. Florida, Alabama and Georgia).

Habitat 

In its natural environment, fishbone fern (Nephrolepis cordifolia) is usually found growing in rocky areas, on rainforest margins, or as an epiphyte on palm trees in the wetter parts of tropical and sub-tropical Australia.

It is mainly a weed of parks, gardens, roadsides, fence lines, disturbed sites, waste areas, railway lines, suburban bushland, riparian areas and coastal environs in sub-tropical and warmer temperate regions.

Habit 

A fern with upright (i.e. erect) or drooping fronds usually growing about 50 cm tall, but occasionally reaching up to 1 m in height.

Impact and control methods 

Fishbone fern (Nephrolepis cordifolia) is regarded as an environmental weed in New South Wales and Queensland.

Stem and leaves 

t forms a network of creeping stems (i.e. rhizomes and/or stolons) and usually develops some fleshy rounded (i.e. spherical) tubers (about 15 mm across). The creeping stems (i.e. rhizomes and stolons) and lower parts of the 'leaves' (i.e. stipes) are densely covered in glossy brown elongated (i.e. linear-lanceolate) scales.

Its upright 'leaves' (i.e. fronds) have a brownish-coloured stalk (i.e. stipe) up to 15 cm long and are divided into numerous alternatively arranged narrow ‘leaflets’ (i.e. pinnae). These ‘leaflets’ (usually 10-35 mm long and 4-11 mm wide, but rarely to 6 cm long) have irregularly and often finely scalloped (i.e. crenate or crenulate) margins and are usually hairless (i.e. glabrous). Their tips (i.e. apices) are relatively broad and somewhat rounded (i.e. obtuse) and their bases are usually somewhat overlapping and slightly lobed on one side. Fronds tend to be dull green in shaded areas and lighter green or yellowish-green when growing in a sunny position.

Flowers and fruits 

Numerous brown, round to kidney-shaped (i.e. reniform), spots will be evident on the undersides of mature fronds. These are the reproductive structures of this species (i.e. sori) and contain the numerous spores. They are partially protected by a tiny kidney-shaped flap of 'leaf' tissue (i.e. a reniform indusium). These reproductive structures (i.e. sori) are arranged in two rows on the undersides of the 'leaflets' (i.e. pinnae), each row being midway between the margin and the centre (i.e. midrib).

Reproduction and dispersal 

This species reproduces by spores and vegetatively via underground stems (i.e. rhizomes) and often also by fleshy underground tubers.

Spores are most commonly spread by wind and water, while the rhizomes, tubers and spores are most often dispersed to new areas in dumped garden waste.

Similar species 

Fishbone fern (Nephrolepis cordifolia) is very similar to several other native ferns (Nephrolepis spp., Pellaea spp., Blechnum spp. and Doodia spp.). The sword ferns (Nephrolepis spp.) are mostly confined to the forests and gorges of northern Australia, and can often be distinguished by their larger fronds with pointed 'leaflets' (i.e. pinnae) up to 10 cm or more long. The sickle ferns (Pellaea spp.) and water ferns (Blechnum spp.) have linear reproductive structures (i.e. sori), often along the margins of their entire 'leaflets' (i.e. pinnae), while the rasp ferns (Doodia spp.) have pointed 'leaflets' (i.e. pinnae) with sharply toothed (i.e. serrate or serrulate) margins.

Fishbone fern (Nephrolepis cordifolia) is also very similar and the introduced and cultivated Boston fern (Nephrolepis exaltata). These two species can be distinguished by the following minor differences:

fishbone fern (Nephrolepis cordifolia) has fronds with 'leaflets' (i.e. pinnae) that overlap at their bases. The tiny flaps of tissue (i.e. indusia) covering its reproductive structures (i.e. sori) are broadly kidney-shaped (i.e. reniform). It often produces round, fleshy, underground tubers.

Boston fern (Nephrolepis exaltata) has fronds with 'leaflets' (i.e. pinnae) that are not overlapping. The tiny flaps of tissue (i.e. indusia) covering its reproductive structures (i.e. sori) are almost circular (i.e. sub-orbicular). It does not produce any underground tubers.