Onoclea sensibilis (Sensitive Fern)
|Also known as:|
|Family:||Dryopteridaceae (Wood Fern)|
|Habitat:||part shade, shade, sun; moist woods, thickets, wet meadows, swamps, pond edges|
|Plant height:||12 to 30 inches|
|Wetland Indicator Status:||GP: FACW MW: FACW NCNE: FACW|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Plants emerge in early spring, typically dark red stems with short white hairs on the back of the unfurling leaves and a few brown scales scattered along the stem. The hairs persist along the leaf veins and midribs.
Leaves and stems:
Leaves are once compound, 12 to 30 inches tall, erect to arching, triangular to egg-shaped in outline, yellowish to medium green. Leaflets are widely spaced, generally lance-elliptic, 5 to 11 on each side of the stem, with a network of veins on the underside. The upper leaflets often have smooth edges while lower leaflets tend to be shallowly to deeply lobed and may be wavy. The stem is dark brown to black and flattened at the base, and winged along much of the upper part of the leaf. One to a few leaves are irregularly spaced along a creeping rhizome.
At least 1 spike, 8 to 20 inches tall, develops in early summer. 5 to 11 pairs of branches contain the spores in bead-like structures tightly packed along a branch. These fertile fronds turn brownish black at maturity and persist through winter, releasing the spores the following year.
Sensitive Fern likely gets its common name from its intolerance for cold, the sterile fronds dying at the first frost. It is easy to identify, as nothing else in Minnesota looks quite like it, though the fertile fronds of Ostrich Fern (Matteuccia struthiopteris var. pensylvanica) are similar and also persist through winter. Ostrich fern has 25 or more pairs of branches on its fertile fronds and is typically taller than Sensitive Fern. Sensitive Fern tolerates both shade and sun and does well enough in a home garden with adequate moisture. The bright green leaves are eye-catching. It can form colonies from its long rhizomes, creating a thick mat of roots.
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Photos by K. Chayka taken in Ramsey County. Photos courtesy Peter M. Dziuk taken in a private garden in Anoka County.
Have you seen this plant in Minnesota, or have any other comments about it?