A climbing fern, or Lygodium, is a genus that has roughly 40 species of ferns. Although these types of plants are called ferns, a climbing fern does not look like a typical fern; it looks more like a vine with big leaves that are further divided into hand-shaped leaflets. Lygodium thrives in tropical regions all over the world, with a small number of temperate species living in eastern North America and eastern Asia. Botanists classify climbing ferns as a member of the family Schizaeaceae.
From their native origin in the tropics, Lygodium found its way to cold climates all over the world because of its sporadic propagation. The spore sacs in the elongated parts of the leaves are easily dispersed by wind. Climbing fern spores easily break loose from their sacs and spread out in the air. The spores are then transported easily to new locations by clinging to vehicles, clothing, and insects.
Similar to vines, climbing ferns work their up by twining around surrounding plants. Fronds, or fern leaves, can grow very long, up to 15 feet (4 m), and are only around 5 inches (12 cm) wide. Depending on the species, the plants can be wiry and thin, with colors ranging from light green to bright orange and turning black during winter. Fronds, vines, and leaflets of climbing ferns are sometimes collected and used as decorations during the holidays.
Some species of climbing ferns are considered a problem-causing invasive plant, particularly in areas located in the southern United States. They have tendencies to invade roadsides and ditches and even natural areas. Lygodium plants can form dense mats in forests and smother shrubs and other small plants. Due to their invasive nature, some Lygodium species are very much disliked in Georgia and Mississippi and even prohibited from being planted in Florida. In Connecticut, on the other hand, one climbing fern species is considered rare and even listed as a species of special concern, as of 2010.
If legally allowed to grow in an area and chosen as a garden plant, climbing ferns must be carefully controlled; otherwise they can grow out of proportion and smother other plants in the garden. Lygodium plants its roots underground and sends up new vines every once in a while, which may need to be cut back and removed by digging them out. These types of fern have small thorns in order to grasp and climb objects to support themselves, so gloves are recommended when working with a climbing fern.