ALIEN FERNS IN HAWAI'I

There has been much confusion about the identity of Nephrolepis species in Hawai'i and which ones are native. Two species are now understood to be indigenous: N. exaltata (Linnaeus) Schott and N. cordifolia (Linnaeus) Presl. The most conspicuous and abundant naturalized species is N. multiflora (Roxburgh) Jarrett ex Morton, reported incorrectly as N. hirsutula or N. exaltata. Nephrolepis multiflora is an aggressive, fast-growing plant. Native to India and tropical Asia, it can be found on all the islands in almost solid stands along roadsides, trail sides, and barren, disturbed soil, such as in fields and orchards. It is a pioneer colonizer of lava flows, often as the only plant and in great quantities. Nephrolepis multiflora is also popular in garden plantings in the ground and in containers. It can be distinguished from the other wild species of the genus most easily by the presence of a line of short erect hairs along the upper (adaxial) surface of the costa. The uniqueness of the species was pointed out by C. V. Morton (1974) . The earliest collection of this species was made by D. Leroy Topping in July 1923 (Topping 2705, BISH). Wagner reported that by 1950 it was only "very localized in the islands" on Kaua'i, O'ahu, and Hawai'i. In Puerto Rico, Proctor calls it the most common fern on the island, even though it probably was introduced only after 1940 (Proctor 1989) . It is no less aggressive in Hawai'i.