Common Fern Moss
Fern Moss family (Thuidiaceae)
This pleurocarpous perennial moss forms a loose mat of evergreen
compound leaves that are green to yellowish green and either
double-pinnate or triple-pinnate. The central stems of these leaves are
up to 8.5 cm. (3½") in length; they are densely covered with narrow
scale-like leaves (perichaetial leaves) up to 0.5 mm. in length that
are long-ciliate along their middle to lower margins (the cilia
resembling hairs). In addition, the larger stem leaves are about 1 mm.
in length, broadly ovate to triangular-ovate in shape, smooth and
revolute (rolled downward) along their margins, and convex on their
outer sides. Under high magnification (40x or more), the outer sides of
these leaves appear minutely bumpy (one swelling per leaf cell). The
midribs of these leaves extend nearly to their tips. Several leafy
primary branches radiate from the central stem of the compound leaf,
becoming shorter as they approach the tip of the central stem; these
primary branches diverge from the central stem at a 45–90° angle. When
they are present, several leafy secondary branches radiate from each
primary branch of the compound leaf, becoming shorter as they approach
the tip of each primary branch; these secondary branches diverge from
each primary branch at a 45–90° angle. The leaves of the primary
branches are about 0.5 mm. in length, while the leaves of the secondary
branches are about 0.3 mm. in length; they are very similar to the
larger leaves of the central stem, except smaller in size.
All of these
leaves share the same axis (alignment) with their respective central
stem or branches, although the leaves diverge somewhat from them when
they are moist. Under dry conditions, the leaves are more appressed and
contracted against the central stem or branches.
Stalks with spore-bearing capsules are
produced infrequently from the leaves of this moss.
When they occur, the elevated stalks (setae) are 1.5–4.5 cm. long,
light green to dull red, terete, and smooth. At the apex of of each
stalk, there is a solitary spore-bearing capsule about 2-4 mm. long.
This capsule is cylindrical in shape and curved to one side; it has a
short-conical lid (operculum) that is covered with a white-membranous
long-beaked hood (calyptra). With age, the capsule and its lid change
from light green to red and the hood slips off. Then the lid falls from
the capsule to release its spores to the wind. The tiny spores are
12-25 microns across, globoid in shape, and smooth. The root system
consists of fibrous rhizoids.
The preference is
partial sun to medium shade, wet to moist conditions, acidic soil
or humus, and some protection from prevailing winds. This fern also
grows on rotting logs and weathered sandstone rock in protected areas that are
shaded and moist, such as wooded ravines.
Common Fern Moss (Thuidium delicatulum)
occasional in the NE, east-central, and southern sections of Illinois,
while in the rest of the state it is uncommon or absent (see Distribution
It has a wide distribution in North
America. Habitats of this moss in Illinois include ground soil and
humus in deciduous woodlands, wooded bluffs and hillsides, northern
edges of pine groves, tree bases near streams in woods, shaded banks of
ravines, shaded creek banks, swampy woods, hummocks in tamarack swamps
and typical swamps, shaded areas of sandstone cliffs, the base of
sandstone walls, wet sandstone boulders in canyons, and
underneath trees in hill prairies along rivers. This moss is found
quality natural areas.
Associations: This moss is often
used as construction material for nests by such songbirds as the Barn
Swallow, Blue-headed Vireo, Northern Catbird, Cedar Waxwing, Eastern
Phoebe, American Robin, Least Flycatcher, Slate-colored Junco, and
Prothonotary Warbler (Breil & Moyle, 1976; Blem & Blem,
When colonies of Common Fern Moss (Thuidium delicatulum)
near streams or pools of water, they are often selected as nest sites
by various lungless salamanders, including the Northern Dusky
Salamander (Desmognathus fuscus), Allegheny Mountain
(Desmognathus ochrophaeus), and Four-toed
(Hemidactylium scutatum); see Hom (1987), Forester
(1979), and Wood
(1955). Common Fern Moss has been found in the digestive tract of a
frozen Woolly Mammoth calf in Siberia, although it is unclear if
this moss was eaten as a source of food or accidentally while consuming
dung (van Geel et al., 2011). Because of its relatively large size and
its tendency to form
colonial mats, this moss provides protective cover to small vertebrate
animals and various invertebrates in shaded wetlands and woodlands.
Location: Along the northern border of a pine
grove at Rock Springs Conservation Area in Macon County, Illinois. The indoor photo was taken with a microscope.
Common Fern Moss (Thuidium delicatulum), also
referred to as Delicate
Fern Moss, resembles the fronds of a small fern, except it forms
colonial mats of leaves, rather than leafy rosettes. It is one of the
more attractive mosses in Illinois. As its common name suggests, Common
Fern Moss is the most
common species of fern moss (Thuidium) in Illinois. Another species in
this genus that is occasionally encountered, Kilt Fern Moss (Thuidium
can be distinguished by the strongly curved tips of its
leaves. Compared to Common Fern Moss, this latter moss also has foliage
that tends to be more yellowish. Early botanical
collections of Common Fern Moss in Illinois during the 19th century
were sometimes misidentified as the Common Tamarisk Moss (Thuidium
tamariscinum); see Lesquereux & Potts James (1884).
This is primarily a European species, although rare collections of this
moss have occurred in Newfoundland and other areas of NE boreal Canada.
past, fern mosses were used to fill chinks in log cabins, as stuffing
for mattresses, and as bedding in cradles and coffins. Today, they are
used as packing material, liners for hanging baskets, soil covers for
potted plants and terrariums, and for ornamental purposes in moss
gardens. Excessive harvesting of such mosses in the wild, however, has the
potential to endanger native populations in some areas.