Ophioglossum pendulum L. Naturalized in Miami, Dade County, Florida

Abstract

Ophioglossum pendulum L. Naturalized in Miami, Dade County, Florida.Ophioglossum pendulum L. has been discovered separately by Adrian Tejedor and Craig Allen, growing on cultivated palm trees in Miami, Florida. Ophioglossum pendulum is an Old World epiphyte, which grows from Madagascar through tropical Asia and into Polynesia. It has been infrequently cultivated in tropical fern collections in Miami since the mid-1970s. This is the first report of established plants growing outside of strictly man-made, horticultural conditions in the New World. This is quite a surprising discovery due to the relative difficulty of maintaining this exotic species in cultivation. Two populations are known in two separate sites in Coral Gables, a community located in southeast Miami. One population (discovered by Adrian Tejedor, in April, 1998) is growing in the persistent leaf bases of Canary Island date palms (Phoenix canariensis) along a public street. In this location, three colonies are on adjacent palms and a fourth is some distance away, in the same row of planted palms. A second, small population, is growing on a sugar palm (Arenga pinnata), inside of Fairchild Tropical Gardens. It was discovered during the summer of 1995, by Craig Allen. In both locations, mature, sporulating plants are growing among the old persistent leaf bases on the palm trunks. Two of the date palm colonies were relatively large and vigorous in 1998, the other two were smaller. The largest colony covered 1.5 square meters of the palm trunk, about ten feet from the ground, with an estimated number of 60 fronds. Considering the slow growth typical of 0. pendulum, this largest colony is estimated to be in excess of 15 years old, and may be much older. In March 1999, only 12 fronds were observed. The majority of the fronds observed the previous year had died and remained in place, completely dried and shriveled. Only the largest fronds bore sporangia. One fertile appendage is borne on the undersurface of the large fronds, which are from 45 to 90 cm. long. Most of the fronds in all the colonies are small, infertile and average 45 cm. in length. Specimens have been taken from this population to document its occurrence and are on deposit at the Fairchild Tropical Garden Herbarium (A. Tejedor, Fairchild Herbarium #81775). In Phoenix and other palm genera, a compact and spongy mass of old leaf bases remains attached to the palm's upper trunk for many years after the leaves are shed. This is where O. pendulum and other epiphytes become established. In the case of Ophioglossum, the dangling fronds are the only visible part of the plant. The rhizome and root system are hidden under the substrate of old leaf bases of the palm. Adventitious shoot buds that develop on the root system eventually produce a colony of plants on the south-east side of the trunk, sheltered by the leaf crown. The dead leaf bases have an ability to remain remarkably wet for days after a rain. The palm leaf-base habitat seems favorable for these ferns, which otherwise may not survive to South Florida's long, late winter and spring, dry season. During the dry winter of 1999 the colonies seemed to have suffered and appeared decidedly smaller. Other epiphytes that coexist with O. pendulum in this habitat are the Boston fern (Nephrolepis cordifolia) and young individuals of Ficus aurea (strangler fig) and 46