FIRST IMPRESSIONS: Onoclea sensibilis is a rambling pinnately lobed fern with soft green sterile fronds. These fronds are deciduous often turning bright yellow before disappearing for the winter. Spores are enclosed in bead-like coverings and are borne on separate upright fertile stalks. This fern forms colonies in rich boggy or moist loamy soils in shade or part shade.
HABITAT & HARDINESS: Onoclea sensibilis occurs in eastern North America from Newfoundland to Florida and west to Manitoba and Texas. For the most part, range occurs east of the Great Plains.
Plants are indigenous to forested river bottoms, vernal ponds, wet to mesic deciduous woods, swamps, moist thickets, moist sandy prairies or savannas, marshes, shaded seeps, wet meadows, stream banks and ditches
Hardiness rating is from USDA Zones 2-10.
PLANT DESCRIPTION: Onoclea sensibilis is a running deciduous fern with separate sterile and fertile fronds. Leaves develop directly from a stout smooth rhizome and are irregularly spaced along its length.
In early spring reddish fiddleheads unfurl into simple lobed or pinnatifid sterile fronds. Each consists of 5-11 pairs of widely spaced narrow lobes. The fronds are up to 3’ long with entire or undulate margins and long petioles.
Both the pinnae tips and indentions or sinuses are rounded. The indentions extend almost to the central stalk leaving a winged rachis.
The deciduous sterile fronds may briefly turn bright yellow but they die to the ground soon after being kissed by the first frost.
The spore bearing fertile fronds are green on emergence in mid-summer. They turn brown or black and remain through most of the winter.
These sporophylls are oblong and about 6” tall. Each bears 5-11 pairs of beaded segments. The closely rolled “beads” wrap around and protect the sori until the spores inside are dispersed by the wind.
Plants usually attain a 12-18” height but in ideal conditions with abundant moisture can reach 3’.
CULTURAL & MAINTENANCE NEEDS: Onoclea sensibilis grows best in dappled to light shade with shelter from prevailing winds.
Plants tolerate acid or neutral sandy or loamy soil. They spread freely from rhizomes as long as soil is rich, loose and moist.
This fern can tolerate some sun if adequate moisture is present. It will also grow well in moist garden soils if irrigated during drought.
This fern is pest resistant and not palatable to deer and other herbivores.
LANDSCAPE USES: The soothing green foliage of this rambling fern make it an excellent Groundcover for a Wetland or wet Shade Garden. In appropriate sites, Onoclea sensibilis matures into a verdant and soothing Mass or Border. This fern can control erosion and is a valuable component of Deer Resistant Plantings, Low Maintenance Plantings, Rain Gardens and Wetlands.
COMPANION & UNDERSTUDY PLANTS: Try pairing with Carex muskingumensis, Chelone glabra, Phlox divaricata or Stylophorum diphyllum.
Matteuccia struthiopteris has similar cultural needs and can be substituted if needed.
TRIVIA: The fertile fronds are picked when young and used in floral arrangements.
The foliage is toxic to horses if eaten in quantity.
Due to fossil records of a similar species, Onoclea sensibilis is thought to be a primitive fern that has changed very little in millions of years. Matteuccia struthiopteris looks very different but is among this fern’s nearest living relatives.
For more information on this plant, visit the USDA PLANTS Database: http://plants.usda.gov/java/profile?symbol=ONSE