The Sword Fern (Nephrolepis exaltata) is a species of fern in the family Lomariopsidaceae (sometimes treated in the families Davalliaceae or Oleandraceae, or in its own family, Nephrolepidaceae), native to tropical regions throughout the world. It is common in humid forests and swamps, especially in northern South America, Mexico, Central America, Florida, the West Indies, Polynesia and Africa. Also known as the Wild Boston fern, Tuber ladder fern or Fishbone fern is in the broader family of sword fern.
The fronds are 50-250 cm long and 6-15 cm broad, with alternate pinnae (the small "leaflets" on either side of the midrib), each pinna being 2-8 cm long. The pinnae are generally deltoid, as seen in the picture to the right. The pinnate vein pattern is also visible on these highly compound leaves. The edges appear slightly serrate. The species has erect fronds, but Nephrolepis exaltata cv. Bostoniensis (Boston Fern), the most commonly cultivated cultivar, has gracefully arching fronds. This mutation was discovered in a shipment of N. exaltata to Boston from Philadelphia in 1894.
Boston fern is native to Florida, the West Indies, and Asian Pacific. A related species, the Tuberous Sword fern (Nephrolepis cordifolia), is frequently confused with Boston fern and is a serious exotic invasive plant, forming dense monocultures.