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DescriptionThis native perennial fern forms a rosette of arching leaves about 3-5' tall. 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 blade of each sterile leaf is up to 4' long, 10" across, and oblanceolate in shape, consisting of 20-40 pairs of leaflets. This blade tapers abruptly toward its tip, while toward its base the leaflets become very small (less than 1" long). Each pinnatifid leaflet is linear-lanceolate in shape and up to 5" long; the larger leaflets have 15-25 lobes. These lobes are oblong-lanceolate, rather short, and smooth along their margins (sometimes with a slight indication of teeth). The sterile leaf blades are medium green and hairless on their upper surfaces, while their lower surfaces are light green and hairless. The venation on the undersides of the lobes is simple-pinnate; the lateral veins are not forked. The central stalk (or rachis) of the sterile blade is light green and glabrous (rarely slightly pubescent); it is channeled on the upper side. The petiole of the sterile blade is up to 1' long, light green to brown, and mostly glabrous; however, young petioles have chaffy scales that are pale orange-brown. The fertile leaves are up to 2' long, 5" across, and oblanceolate or oblong; they soon become dark brown. Each fertile blade has 10-25 pairs of leaflets that are ascending and contracted; the lobes of these leaflets have a bead-like shape. The sori (spore-bearing structures) are located on the undersides of these bead-like lobes. The petioles of the fertile blades are dark brown and rather stout at the base. 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 fertile leaves until the early spring; 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 vegetative clones of the mother plant.