Nephrolepis exaltata, known as the sword fern It is native to the Americas.

Description

The fronds of Nephrolepis exaltata are long and broad, with alternate pinnae (the small "leaflets" on either side of the midrib), each pinna being long. The pinnae are generally deltoid, as seen in the adjacent picture. The pinnate vein pattern is also visible on these highly compound leaves. The edges appear slightly serrate, linear to lanceolate and glandular. The rachis bears monochrome sprout soups. The leaflets are entire, undestroyed and oblong-lanceolate up to long and up to wide. They stand at a distance of less than . The sori are rounded. The spores are warty and wrinkled. Nephrolepis exaltata forms an underground rhizome that is slim and tuberous.

The species has erect fronds, but Nephrolepis exaltata 'Bostoniensis' (Boston fern) and 'Teddy Junior' have gracefully arching fronds. This mutation was discovered in a shipment of N. exaltata to Boston from Philadelphia in 1894. Other proposals for the origin of the term Boston fern were documented by David Fairchild, who stated that the term came from Florida pioneer nurseryman John Soar, who sent the plants to his friend in Boston.

Range

The fern is common in humid forests and swamps, especially in northern South America, Mexico, Central America, Florida, the West Indies, Polynesia and Africa. N. exaltata thrives in moist, shady locations and is found frequently in swamps and floodplains. The plant can grow both terrestrially and as an epiphyte. It grows epiphytically on the Sabal palmetto.

Subspecies

Two subspecies are accepted: The plant is usually propagated by division of the rooted runners, as named cultivars will not produce true spores. It is safe for pets as it is known to be non-toxic.

Cultivars

A number of cultivars exist:

  • 'Teddy Junior'
  • 'Bostoniensis'
  • 'Sonata'
  • 'Montana'
  • 'Green Lady'
  • 'Marissa' (a dwarf variety)
  • 'Todeoides'
  • 'Whitmanii Improved'
  • 'Rooseveltii'

The following are recipients of the Royal Horticultural Society's Award of Garden Merit:

  • Nephrolepis exaltata
  • Nephrolepis exaltata 'Bostoniensis'
  • Nephrolepis exaltata 'Elegantissima'

Invasive species

A related species, Nephrolepis cordifolia (Tuberous sword fern), is frequently confused with this sword fern, and is a serious exotic invasive plant, forming dense monocultures.

Nephrolepis exaltata is classified as an invasive alien plant in South Africa. In some provinces it must be eradicated by law. In others, a permit is required to import, possess, grow, breed, move, sell, buy or accept one as a gift.

References

  • Floridata: Nephrolepis exaltata