Dryopteris intermedia

Dryopteris intermedia intermediate fern

The delicate green fronds of this common overwintering fern rise in upright circular clusters from a central rhizome. The jagged teeth on the pinnules give this fern a lacy appearance.

Habitat & Range

Moist or dry rocky woods, especially hemlock-hardwood forests; ravines, and rock ledge. Prefers soils rich in humus.

Range is from Newfoundland to Washington and Alaska, south along the Alleghenies to NC and TN and to Ohio and Nebraska.

Wetland Code: FAC

Phenology

This fern overwinters.

Characteristics

Fronds 13-35 in. long, 4 to 10 in. wide.

Blade oval to narrowly triangular, middle to lower pinnae nearly the same length; with glandular hairs mostly on rachis, costa and indusia. Cut into 10-20 pairs of pinnae, primarily opposite.

Pinnae oblong, paralle sides for more than half of length, shorts stalks; extens out at right angles to rachis, but in same plane. Basal pinnae somewhat asymmetrically triangular, but same length as other pinnae. Costae have glandular hairs.

Pinnules innermost pinnules (closest to rachis) of basal pinnae slightly shorter or same length as adjacent pinnules on same side of costa; lower innermost pinnules in basal pinnae longer but less than twice as long as upper innermost pinnules. Margins toothed, bristle-tipped. Pinnules on lower pinnae sometimes cut almost to center, the most dissected of the Dryopteris species.

Rachis with glandular hairs.

Stipe 1/3 to 1/4 of frond length, light brown scales at base of stipe, scattered above

Rhizome thick, coarse, scaly and erect.

Sori small, between midvein and margin. Indusia with glandular hairs most visible early in season, obscure later.