Description: This 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.
Cultivation: The
preference is light shade or dappled sunlight, wet to moist conditions, and
soil that is mucky or sandy. Average moisture conditions are tolerated if this
fern is watered during dry spells. The leaves are delicate and easily damaged.
In more heavily shaded areas, Ostrich Fern often fails to produce fertile
leaves.
Range &
Habitat: Ostrich Fern occurs in widely scattered locations in
northern and western Illinois, where it is rare (see
Distribution
Map); elsewhere in the state, it is absent from natural areas. Habitats
include moist rich woodlands, swamps, and soggy thickets in both sandy and
non-sandy areas. Ostrich Fern is circumboreal in its distribution, occurring in
parts of North America, Eurasia, and East Asia. The North American variety is
identified as var. pensylvanica. This fern is often cultivated in
gardens and along the foundations of houses and other
buildings.
Faunal Associations: The
caterpillars of the Ostrich Fern Borer Moth (Papaipema sp.) bore through
the stalks and/or root system. This rare moth is found in the New England area
of the United States, where the Ostrich fern is more common, although it has
not been found in Illinois to my knowledge. Because this fern has large leaves
and often forms vegetative colonies, it can provide substantial cover to
various kinds of wildlife where it is locally common.
Photographic Location: On the grounds of Japan
House, which is located at the Arboretum, University of Illinois, in
Urbana.
Comments: This a lovely fern
with tall arching leaves. It is relatively easy to identify because of the
oblanceolate shape of its large leaves, which have very short leaflets (pinnae)
toward the base of the blades. Very few species of ferns have such short
leaflets. One of them, Thelypteris noveboracensis (New York Fern), has
elliptic leaves that taper very gradually toward both their bottoms and their
tips. The leaves of Ostrich Fern, in contrast, taper abruptly toward their
tips. Another distinctive characteristic is the simple-pinnate venation on the
undersides of the leaflet lobes, where the lateral veins are undivided and
straight. Other similar ferns (e.g., Osmunda spp.), often have forked
lateral veins on the undersides of their leaflet lobes. The small fertile
leaves in the center of the rosette have a rather peculiar appearance, although
they are often hidden by the larger sterile leaves.