Nephrolepis exaltata

Smith, Alan R. & Kessler, Michael, 2018, Prodromus of a fern flora for Bolivia. XXXVII. Nephrolepidaceae, Phytotaxa 334 (2), pp. 135-140 : 137

Nephrolepis exaltata (L.) Schott, Gen. Fil., t. 34. 1834.

Range: — U.S.A. (Florida), Antilles; southern Mexico; French Guiana, Bolivia (LP), and Brazil; Old World tropics, by virtue of occasional naturalization of cultivated plants; an endemic subspecies, subsp. hawaiiensis W.H.Wagner , is attributed to Hawaii ( Palmer 2003). Native range uncertain, but occasionally introduced and naturalized in many places (e.g., in Mexico; Mickel & Smith 2004).

Ecology:—Cultivated in cities; 2600 m.

Notes: —This species is often attributed a pantropical distribution by virtue of widespread naturalization, but specimens of this are often misidentified in herbaria and are referable to other species. In particular, N. exaltata has been confused with the Old World N. hirsutula (G.Forst.) C.Presl. The original Boston fern (‘Bostoniensis’) was reportedly from a shipment of N. exaltata sent to Boston from Philadelphia in 1894 ( Kessler 2004). It is commonly believed that N. exaltata has given rise to cv. ‘Bostoniensis’ and perhaps many other cultivars as well, but other species are now known to have been involved ( Yahaya et al. 2016). Even the origin of N. exaltata is uncertain, and some evidence suggests that the species called this is of hybrid origin itself ( Hennequin et al. 2010, Yahaya et al. 2016), perhaps with N. cordifolia as its maternal parent and N. biserrata as the paternal parent. Cultivars of N. exaltata and other Nephrolepis species have been propagated and sold in nurseries, e.g., ‘Bostoniensis’ (Boston fern) and ‘Whitmanii’ (see Hoshizaki & Moran 2001), but the parentage (origin) of many of these is still unclear. Large & Farrington (2016) recently addressed the complex issues of the identification of cultivars of Nephrolepis (especially of N. exaltata and N. cordifolia ) naturalizing in New Zealand; Yahaya et al. (2016) discussed similar issues of hybridization and cultivar origins in a global sampling of Nephrolepis , including cultivars.