Sensitive Fern (Onoclea sensibilis)

Sensitive Fern (Onoclea sensibilis)

Sensitive Fern (Onoclea sensibilis), sometimes called the Bead Fern, is a deciduous, perennial, wetland fern in the Wood Fern (Dryopteridaceae) family and order Polypodiates (True Ferns). Some authorities place this forb/herb in the Onocleaceae family. The genus name is from a name given to a plant of obscure identity by the Roman/Greek botanist, Pedanius Dioscorides. The species name is from the Latin for "sensitive." The species name comes from the fact that this fern is sensitive to frost. The family name is from the Latin for a wood nymph. This fern can have a number of forms depending upon the habitat. The variety described on this page is an emergent form found on the banks and shallow water of a pond. The photographs on this page were taken in or around French Hill Pond. Forms in drier (but still wet) habitat will have finer fronds. The sori (clusters of structures producing and containing spores) are formed in late summer on fertile fronds and look like beads, hence its alternative common name. In early spring, the fronds may be outlined in pink as shown in the photograph below.

Sensitive Fern (Onoclea sensibilis)

The sterile fronds are yellow-green and can grow to as much as a yard (90 centimeters) long. The emergent variety sterile fronds found on the shores of French Hill Pond are much smaller. The fertile fronds begin as very small green structures that turn black at maturity. The segments of the mature fertile fronds reform to make the beaded structures in which the spores develop. The spores overwinter and are released at maturity in early spring to propagate the plant. The following photograph shows the beaded structure containing the spores. This photograph was taken in October. Note a portion of a sterile fond in the foreground.

Sensitive Fern Spore Structure

In an early stage of development, the fronds are curled into a fiddlehead form. The following photograph shows sensitive ferns on the bank of French Hill Pond. Note that these land ferns are larger than the ferns at water's edge.

Sensitive Fern on Land

The root system is a rhizome, which is also a means by which this fern propagates .The rhizomes help stabilize the soil.

The fiddlehead form of this fern is used as food. CAUTION: this fern is labeled as toxic by some authorities. These fiddleheads used for food should be thoroughly washed, descaled and steamed to eliminate pathogens and the toxin thiaminase an enzyme that removes vitamin B from the human body and may be found in some ferns. Some people eat fiddleheads raw without ill effects. However, this practice is not recommended. The Sensitive Fern is cultivated as an ornamental plant in wet areas of a landscape. However, it can be very aggressive. Indigenous Americans used this plant for medicinal purposes.

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