What is a Sensitive Fern?

The sensitive fern, also known as the bead fern, mead brake, or by its scientific name Onoclea sensibilis, is the lone species of the genus Onoclea. A sensitive fern is distinguished from other ferns by its coarse, divided leaves that are called fronds. This deciduous and perennial fern received its common name because of its sensitivity to frost. It is a medium to large type of fern that can reach up to 2 feet (0.6 m) tall and wide. The natural habitat of this plant is confined to eastern North America and eastern Asia.

This fern is susceptible to drought and sandy soil. The sensitive fern wilts under hot conditions and grows best in sub-tropical climes. It prefers damp, acidic, or well-drained soil under full sun or partial shade.

A sensitive fern grows in large, spreading colonies. Single fronds emerge from horizontal underground stems 0.1 to 0.2 inches (4 to 7 mm) thick to form green foliage that turns deep brown in color upon maturity. The coarse-looking fronds are bright green in color. Each frond has a triangular outline with wavy leaflets. Young fronds point downward rather than upward like adults.

The leaflets of each frond grow in eight to 12 opposite pairs up to 1 foot (0.3 m) long. They have prominent veins coming from a single straight vein along each frond. Hair-like projections give the underside of the leaflets a rough texture. Its fertile leaves develop hard, spherical, bead-like structures that encapsulate the fern’s spores. These stalks break open during spring to release spores for germination.

During the Tertiary Period, sensitive ferns grew in North America, Greenland, and Japan. At the start of the 20th century, the species’ habitat was restricted to eastern parts of North America and Asia, though it is now cultivated in Western Europe. The sensitive fern can be found in moist environments, such as marshes, woods, and swamps.

The sensitive fern is one of the most common ornamental plants used in gardens and homes and as an accent in flower arrangements. This fern is also used as ground cover because of its widespread growth. It should be regularly trimmed, as it exhibits weed-like behavior and may take over whole gardens. This plant can tolerate warm conditions as long as the soil is watered on a regular basis. The sensitive fern is vulnerable to attacks by insect pests such as the corn earworm and fall armyworm, as well as leaf blister fungus.