More on the Spread of Nonnative Ferns in Georgia and the Southeastern United States

Abstract

Relative to other vascular plants, ferns have been overlooked with respect to the potential for nonnatives to spread into natural areas and potentially displace native species. An unusual site in the Piedmont of northeast Georgia was found to harbor two species of nonnative ferns that have clearly become naturalized. A third species at the site represents the appearance in a natural setting of another nonnative fern species whose cultivars and hybrids are being more widely planted as ornamentals. Examination of herbarium specimens from Georgia and the Southeastern United States clarified the status of some earlier records and some overlooked records, based on misidentifications or questionable status as naturalized. The species involved (Arachniodes simplicior, Polystichum polyblepharum, and Anisocampium niponicum (=Athyrium niponicum)) are all introductions from temperate regions in East Asia and probably represent escapes from cultivation via spores. The appearance of these species in natural communities raises questions about their potential to spread farther and to become pests by crowding out native flora. The invasive potential of these three species and five other species discussed in a previous paper is evaluated based on field observations as well as information about their status as an epiphyte or ground dweller, reproductive plasticity, ecological requirements, and popularity as horticultural ornamentals.