Sword fern

Appearance

The fronds of ''Nephrolepis exaltata'' are 50–250 cm long and 6–15 cm broad, with alternate pinnae , 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'' 'Bostoniensis' , has 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 the term came from Florida pioneer nurseryman John Soar who sent the plants to his friend in Boston.

Uses

''Nephrolepis exaltata'' is a very popular house plant, often grown in hanging baskets or similar conditions. It is a perennial plant hardy in USDA plant hardiness zones 9-11. Although the fern may appear totally dead due to frost, it will re-emerge in the spring. In general, the Boston fern likes damp, but not soggy soil that is rich in nutrients. Of the common cultivated ferns, the Boston fern is the most tolerant to drought. The fern thrives best in humid conditions, so when grown as a house plant it becomes necessary to mist the plant when relative humidity falls below around 80%. Although outdoors this plant prefers partial shade or full shade, inside it grows best in bright filtered light. This plant is usually propagated by division of the rooted runners, as named cultivars will not produce true spores.

It is safe for cats to eat as it is known to be non-toxic.

;Invasive species

A related species, ''Nephrolepis cordifolia'' , 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, by law, be eradicated. In others, a permit is required to import, possess, grow, breed, move, sell, buy or accept one as a gift.