Onoclea spp.

sensitive fern

Onocleaceae

Eastern North America and eastern Asia

Deer Resistant

Native to North America

SunFull Sun – Part Shade – Full Shade

WaterHigh

HardinessZones 4–9

Overview

Onoclea spp. is a genus in the family Onocleaceae, usually treated as monotypic with the single species O. sensibilis, the sensitive fern, native to eastern North America and eastern Asia. It is a deciduous fern that spreads by long, branching rhizomes to form colonies in wet ground. The sterile fronds are broadly triangular, 30-100 cm (12-40 in) tall, deeply pinnatifid with nearly opposite, wavy-edged segments and a winged central stalk, rising singly along the rhizome on yellow-green stalks. Separate fertile fronds are shorter, erect, and woody, with the segments rolled into hard, bead-like structures that enclose the spores; these fertile fronds turn brown and stand through winter, releasing spores the following spring. The common name refers to the sterile fronds, which blacken and collapse at the first autumn frost. The fern grows in marshes, wet woods, ditches, and streamsides in sun or shade, and spreads quickly in moist, open ground, where it can crowd out smaller plants. The foliage is reported to be poisonous to horses.

Native Range

Onoclea sensibilis is native to eastern North America, from Canada south to the Gulf states, and to eastern Asia including parts of China, Korea, and Japan. It grows in marshes, wet woodland, ditches, and along streams and pond edges.

Suggested Uses

Onoclea sensibilis is used in bog gardens, pond and stream margins, rain gardens, and damp shade where a spreading groundcover fern is wanted. Its rhizome-forming habit suits erosion control on wet banks but makes it too vigorous for small, mixed plantings.

How to Identify

The fronds are dimorphic: broad, triangular, deeply lobed yellow-green sterile fronds 30-100 cm (12-40 in) tall with a winged central stalk, and separate shorter, erect fertile fronds bearing hard, bead-like segments that turn brown and persist through winter. The sterile fronds rise singly along a creeping rhizome and blacken at the first frost.

Appearance

Size & Dimensions

Height1' - 3'4"

Width/Spread2' - 4'11"

Colors

Foliage Colors

green

Fall Foliage Colors

yellow

brown

Bloom Information

As a fern, Onoclea sensibilis does not flower. Spores form inside the bead-like segments of the fertile fronds, which develop in late summer, persist over winter, and shed spores the following spring.

Detailed Descriptions

Foliage Description

yellow-green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade SunFull Shade

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.0 - 7.0(Neutral)

357912

Soil Types

loam clay peat

Drainagewet

Water & Climate

Water Needs

High

Frost Tolerance

hardy

Care & Maintenance

Care Guide

Onoclea sensibilis grows in full sun to full shade in consistently moist to wet, humus-rich soil with an acidic to neutral pH of about 5.0-7.0, and it tolerates standing water and heavy clay. With ample moisture it spreads rapidly by rhizome and can become invasive in beds, while in drier soil it stays shorter and less vigorous. It is hardy through USDA zones 4 to 9 and dies back completely at the first frost. The fronds scorch in dry, exposed sites, so steady moisture and shelter hold them in condition. Colonies are reduced by digging out sections of rhizome.

Pruning

No pruning is needed during the growing season. The blackened sterile fronds can be cleared after frost, while the persistent fertile fronds are left in place until spring so they shed their spores; spread is controlled by lifting and removing rhizomes.