- Onoclea, from the Greek onos
(onos), "vessel," and kleio
(kleio), "to close", referring to the closely rolled fertile fronds.
- sensibilis, from the Latin, "sensitive"
- Common Name, from the observation of early settlers that it was very
sensitive to frost, the fronds dying quickly when first touched by frost.
- Other common names include Bead Fern, Meadow Brake, Onoclée
- A , , ¾, º, é
- A deciduous, coarse textured, perennial fern, with broader leaves and
pinnae (leaflets) than most other North Country ferns; 18"-24"
- Sterile Fronds light green, leathery, broad, and almost triangular,
typically tilted up and back.
- Petiole (leaf stalk) brittle, smooth, and usually
longer than blade with a shallow furrow in front; yellow/pale tan, and
dark brown at base with a few scales.
- Blade of 8-12 pairs of nearly opposite leaflets with
wavy margins, prominent network of veins, and sparse white hairs on
- Rachis (axis) winged, more broadly toward tip.
- Pinnae (primary leaflets) lanceolate to oblong, with
or without teeth or with a few undulations. Lower leaflets long and
tapered at both ends; upper leaflets with little or no tapering toward
- Pinnules (secondary leaflets) blades mostly 4"-12"
long, 4"-14" wide, with 8-12 pairs of opposite pinnae, these
sinuate to pinnatifid, ½"-1¼" wide, sparsely
white-hairy on the veins beneath; petioles shorter to about as long
as the blade.Sterile leaves yellow-green, deltate, coarsely divided,
5"-13½" × 6"-12". Petiole of sterile
leaf black, 22--58 cm, flattened at base; rachis winged, becoming broader
toward apex. Pinnae 5--11 per side, lanceolate; proximal pinnae 9--18
cm, margins entire, sinuate, or laciniate.
- Fertile Fronds brown, shorter than sterile leaves (approximately
1' tall), and structurally unlike the green sterile fronds. Fertile fronds
produced Aug--Sep, often persistent into the following year.
- Petiole (leaf stalk)Petiole 19--40 cm, base sparsely
- Rachis (axis)
- Pinnae (primary leaflets) numerous, compact, upward-pointingPinnae
linear, 5--11 per side, 2.5--5 cm; pinnae strongly ascending, 2-5 cm
long, Sporophyll leaves green, becoming black at maturity, oblong, 7--17
× 1--4 cm.
- Pinnules (secondary leaflets) many hardened, beadlike
subleaflets that become dark brown when mature. ultimate segments revolute
to form beadlike structures, 2--4 mm diam.divided into bead-like pinnules
with inrolled margins enclosing the sori, the pinnules 3-4 mm wide,
becoming dry, hard, eventually separating to release the spores;
- Sensitive fern is easily killed with the first frost, leaving behind
the stiff, beaded fertile stalks. blade pinnate-pinnatifid, mostly 5-15
- Root System of creeping rhizomes 4mm-7mm thick, growing near the
soil surface; stout, brown, smooth, and extensively branched and spreading.
Numerous roots grow along the rhizomes and produce a fibrous mat.
- Fiddleheads The curled leaves (fiddleheads) emerging
from rhizomes form a distinctive, pale red mass in the spring
- Fruit spore cases produced within the hardened, beadlike sections
of the fertile leaflets, becoming dark brown at maturity. sori globose,
covered by a delicate, hoodlike indusium.
- Sori clustered like beads or grapes on the upright
- Spores minute, on separate fertile fronds, within
bead-like modified leaflets
- Leaf forms with pinnae intermediate between those of sporophylls and sterile
leaves, or with pinnae fertile only on one side of the blade, can occur
on plants that also bear normal leaf forms.
- As with Matteuccia struthiopteris,
sporophylls of Onoclea sensibilis persist through the winter and
release the green spores in spring before the sterile leaves expand.