Royal Fern family (Osmundaceae)
Description: This native perennial fern consists of a loose rosette of sterile leaves about 2-4' tall; these leaves are ascending to nearly erect. In the middle of this rosette, fertile leaves are produced during the spring or early summer; they are erect and somewhat shorter than the fertile leaves. The sterile leaves are pinnate-pinnatifid and oblong-lanceolate in outline; each of these leaves has about 15-25 pairs of leaflets along the central rachis (or stalk). Each of the pinnatifid leaflets has about 10 pairs of lobes and tapers gradually to a point; individual leaflets are linear-lanceolate in outline. At the base of each leaflet underside (at the junction of its stalk with the rachis), there is a persistent tuft of hairs. The individual lobes of each leaflet are short-oblong in shape and their margins are smooth or slightly ciliate; the tips of the lobes are more or less well-rounded. On the underside of each lobe, there is pinnate venation consisting of a straight central vein and forked lateral veins. Sterile leaves are medium green and mostly hairless, although the rachis of young leaves is often slightly woolly. Each sterile leaf has a petiole (or stipe) at its base that is brown-woolly, particularly when it is young. The fertile leaves have the same pinnate-pinnatifid structure as the sterile leaves, but their contracted leaflets are covered with brown sporangia (which become more dark with age). These small sporangia are globoid in shape and divide into 2 parts to release the spores during the summer. These tiny spores are distributed by the wind. The root system consists of a crown of fibrous roots, from which spreading rhizomes are occasionally produced.
Cultivation: The preference is dappled sunlight to light shade, consistently moist conditions, and an acid soil with some sand and organic matter. This fern likes sheltered locations with high humidity.
Range & Habitat: Cinnamon Fern is occasional in southern and northern Illinois, uncommon in west-central Illinois, and absent from the central and east-central sections of the state (see Distribution Map). This fern has a wide distribution in North America; it also occurs in South America and Asia. Habitats include low sandy woodlands, moist sand prairies, swamps & bogs, seeps and springs in wooded areas, moist sandstone ledges in partially shaded areas, and sandstone ravines. This fern is found in high quality natural areas. It is occasionally cultivated in moist shade gardens.
Faunal Associations: The following insects feed on the Cinnamon Fern and other Osmunda spp.: Olethreutes osmundana (Tortricid Moth sp.), Papaipema speciosissima (Osmunda Borer Moth), and Zonothrips osmundae (Osmunda Thrips). The latter insect was originally found on Cinnamon Fern at Volo Bog in NE Illinois.
Photographic Location: A sandstone ledge along a ravine at The Potholes in west-central Indiana.
Comments: This large fern has fertile leaves that are unusually showy; they become reddish brown at maturity. The sterile leaves are equally attractive. When the fertile leaves are present, Cinnamon Fern is easy to identify. When fertile leaves are absent, it is difficult to distinguish this fern from Osmunda claytoniana (Interrupted Fern). On sterile leaves, the Cinnamon Fern has persistent tufts of hair at the base of its leaflets (on their undersides), whereas the leaflets of Interrupted Fern lack such tufts of hair. The lobes of Cinnamon Fern's leaflets are slightly more pointed than the lobes of Interrupted Fern, although this distinction is not always reliable. Ferns in the Osmunda genus have forked lateral veins on the leaflet undersides (where the lobes occur) of their sterile leaves; these veins have the shape of a tuning fork. Other ferns usually lack such veins. Fossil records indicate that ferns in the Osmundaceae (Royal Fern family) are among the oldest of ferns; today's survivors can be regarded as living fossils.