March 2021 • Nebraskaland 49
southward into the plains and their population grew, their
use of fi re would sway the battle in favor of grass over tree.
Today, Rock Glen's vegetation remains similar to that
viewed by recent Plains Tribes. Open stands of bur oak,
known as savanna, shelter in the less fi re-prone ravines and
canyons, and in the deepest canyons, the fi re-sensitive green
ash, hackberry, elms and eastern red cedars grow with oaks.
Under this canopy thrive hairy woodbrome, Sprengel's sedge,
wild strawberries and other woodland plants.
In the partially-shaded oak savanna, fi re-hardy and sun-
loving tallgrass prairie plants mingled with the woodland
fl ora and spread upward over the hills. Among the tallgrass
fl ora are the chest-high big bluestem and Indian grass along
with plentiful wildfl owers. On dry, wind-swept ridge tops
and steep, eroded slopes, tallgrass prairie surrenders to more
drought-tolerant mixed-grass prairie. Here, on shallow, sandy
soil, the knee-high side-oats grama and little bluestem rise
above an underlying carpet of buff alograss and hairy grama.
A unique, but sparse fl ora of side-oats grama, catclaw
sensitive briar, cobaea penstemon, dotted gayfeather and
aromatic aster occupy the small shale fl ats interspersed in
the prairie.
Sedges, rushes, marsh and sensitive fern, the rare bushy
seedbox and other wetland plants grow in soggy soils
bordering spring seeps and the rivulets draining them. The
seeps originate from
rainwater and snowmelt
that percolates
downward through
porous sandstone until
it reaches impervious
shale. The groundwater
fl ows atop this layer,
seeping out in ravines
and on low hillsides.
The rivulets eventually
gather, forming shallow,
stony-bottomed creeks
that wind through Rock
Glen.
Adding uniqueness
to the local fl ora, the
sandstone outcrops and
soils provide habitat
for many plant species
otherwise rare or absent
in Nebraska. Among these
is the diminutive bird's-foot violet. It was fi rst discovered in
the state in 1987 growing on a thin-soiled prairie in Steele
City Canyon a few miles southeast of Rock Glen. A second
A Dakota sandstone cliff . Dakota sandstone and shale lie just below the soil surface at Rock Glen.
A colony of bird's-foot violet
grows in rocky, hilltop prairie.
PHOTO
BY
GERRY
STEINAUER
