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| Lygodium, the Climbing Ferns | ||||||||||||
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 Climbing Fern, Lygodium palmatum | ||||||||||||
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The climbing ferns are an unusual group of plants of tropical zones, with one temperate and one subtropical species. They are unique among plants in that the rachis, or midrib, of the frond is thin, flexible, and long, with the frond unrolling with indeterminate growth, with the rachis twining around supports, so that each frond forms a distinct vine. The fronds may be from three to ten meters long, depending on the species.
The one temperate species, the American climbing fern, Lygodium palmatum (shown in photograph), is rare throughout its range in the United States and requires intensely acid soil. Two other species -- Lygodium japonicum and Lygodium microphyllum -- on the other hand, are exotic weeds throughout the deep south of the U. S., growing in a variety of soils.