The two species of Pityrogramma found in Hawai'i are introductions from the Americas and have in the past been considered to be varieties of a single species, P. calomelanos (e.g., by Tryon & Tryon [1982]). Recently the two have been recognized as distinct species, which, when growing together, frequently hybridize to produce sterile offspring. Early reports, which treated these two as a single species, failed to note the color of the coating on the underside of the frond. In such cases it is not possible to know which of the two is being referred to; without documenting specimens the reports may refer to either species. Wagner (1993) published a key that detailed the differences between the two species, as well as their hybrid.

Pityrogramma austroamericana Domin [Syn. Pityrogramma calomelanos (Linnaeus) Link var. aureoflava (W. H. Hooker) Weatherby ex F. M. Bailey], Goldfern, native to tropical America, was first wild-collected on Kaua'i in 1903 (Brodie Sept. 13, 1903, BISH). This very popular cultivated fern was naturalized on all of the main islands by 1950, where it prefers to grow on bare roadside banks and trail sides, and in open, disturbed areas. The fronds of the mature goldfern are spreading, not erect, and mostly bipinnate. In horticulture, this fern is widely incorrectly known as P. hybrida.

Pityrogramma calomelanos (L.) Link, Silverfern, also from tropical America, probably made its appearance in the Hawaiian landscape at about the same time as the goldfern. Like the goldfern, this species was very popular in cultivation. The earliest wild collection that I have seen was made in 1908 on O'ahu, in Punalu'u Valley (Rock 13, BISH). The silverfern grows in areas similar to those of the goldfern but tends to favor shadier conditions. It has fronds that are erect or arching and frequently three-pinnate. It is found less frequently than the goldfern and seems to have become even less common in recent years.

Wherever the goldfern and silverfern are found growing together, hybrid intermediate plants are frequently found. These vigorous hybrids, recently named Pityrogramma x mckenneyi W. H. Wagner (1993), produce sterile spores but reproduce vegetatively by root proliferations.