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.