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Wetland Plants and Plant Communities of Minnesota and Wisconsin


(Onoclea sensibilis L.)

Sensitive fern



FIELD CHARACTERISTICS: This colonial fern supports very dissimilar sterile and fertile fronds. Sterile fronds (leaves) are up to about 60 cm. tall, deciduous (very sensitive to frost), 18-40 cm. x 15-35 cm., leathery, light green in color, and simple. The deeply pinnatifid leaflets occur as 8-12 paired segments, 1.5-5 cm. wide, with a characteristic net venation. The upper side of leaflet is smooth and the bottom side has scattered white hairs, usually on the veins. The rachis is broadly winged as are the upper leaflets. The fertile fronds are produced beginning in midsummer, turn dark brown at maturity, and persist through winter. They grow to about 30 cm. tall and are upright with many short leaflets that form small, inrolled bead-like divisions (pinnules). These divisions contain the spore cases. A mass of pale red fiddleheads form in the spring.

ECOLOGICAL NOTES: Sensitive fern primarily occurs in wooded swamps, alder thickets and shrub-carrs, particularly near their borders. It also occurs in marshes and along edges of shaded ponds.

SOURCE: Gleason and Cronquist (1991); and Tryon (1980).

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