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This perennial fern develops either individual leaves or a rosette of arching leaves about 3-5' tall during late spring. The compound leaves are pinnate-pinnatifid and dimorphic; the sterile leaves are much larger than the fertile leaves in the center of the rosette. The sterile leaves are up to 5' long, 12" across, and oblanceolate in outline, consisting of 20-50 pairs of leaflets. The sterile leaves taper abruptly toward their tips, while toward their bases the leaflets become very small (less than 1" long). Individual leaflets are up to 6" long, linear-oblong in outline, and deeply pinnatifid with 15-40 pairs of lobes. These lobes are short-oblong to ovate in shape, while their margins are smooth and folded downward. The sterile leaves are medium to dark green and glabrous on their upper surfaces, while their lower surfaces are light to medium green and glabrous. The venation on the undersides of lobes is simple-pinnate; the lateral veins are not forked. The rachises (central stalks) of sterile leaves are light green and glabrous (sometimes becoming finely short-pubescent below); the upper surfaces of these rachises are furrowed, angular, and somewhat flattened, while their lower surfaces are convex. The petioles of the sterile leaves are relatively short (2-12" in length), light green to brown, and relatively stout; they are usually glabrous or finely short-pubescent, although young petioles have chaffy scales that are pale orange-brown. The fertile leaves are up to 1½' long, 4" across, pinnate-pinnatifid, and oblanceolate or elliptic in outline. Immature fertile leaves are greenish, while mature fertile leaves become dark brown. The fertile leaves have 10-30 pairs of leaflets that are ascending and contracted. The lobes of these leaflets are bead-like in shape from the presence of sporangia (spore-bearing structures); there are up to 30 pairs of lobes per leaflet. The petioles of fertile leaves are 2-8" long, greenish to dark brown, and rather stout at their bases. The fertile leaves are produced during mid- to late summer; immature or weak plants often fail to produce them. The spores aren't released from the sporangia of fertile leaves until the early spring, when they are distributed by the wind. The sterile leaves are deciduous and die down during the winter. The root system consists of a stout vertical rootstock with a dense mass of fibrous roots; long rhizomes occasionally develop from the rootstock, forming cloned offspring of the mother plant. Cultivation


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© John Hilty

Source: Illinois Wildflowers

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