By Bill Ward
Published in The Boerne Star in July 2005
For me the most beautiful spots in the Texas Hill Country are where shallow, spring-fed streams flow through narrow limestone canyons. These scenic jewels are home to some of our most interesting and unusual native plants. Most of these sites are protected on private land, hidden away from the highway routes.
Recently, I was lucky enough to accompany Chad Norris, Texas Parks and Wildlife biologist, Jason Singhurst, TP&W botanist, and Bill Carr, Texas Nature Conservancy botanist, when they visited some springs on ranches in Bandera and Real Counties. Norris has permission from many ranchers to monitor their springs as part of his extensive study to gather hydrologic and biologic baseline data for those little-studied smaller springs of the Edwards Plateau.
These ranchers recognize the importance of documenting and preserving small springs, which are in danger of vanishing as more groundwater is sucked up in the wake of the population explosion across the Hill Country. In the interest of protecting these small springs, as well as in consideration of the landowners’ privacy, the policy of Norris and other TP&W scientists is never to publish the exact locations of the springs from which they gather data.
In the southeastern Hill Country, many of the springs issue from permeable and porous layers of the basal part of the Edwards Formation that lies on top of more impermeable layers of the uppermost Glen Rose Formation, or where it is present, the Walnut Formation. Water collects in the Edwards limestones and flows underground across the top of the Glen Rose or Walnut marls (clayey limestones). In certain places where stream erosion or karst solution has exposed the lower Edwards layers, the groundwater may flow out of the rock as springs. Upstream above the springs, the limestone canyons are dry much of the year.
The spring-fed canyons are wonderlands of floral diversity. Moist canyon walls are draped with pendulous maidenhair fern (Adiantum capillus-veneris), and stream banks are lush with upright shield fern (Thelypteris kunthii) and a variety of sedges (family Cyperaceae).
One of the canyons we visited in Bandera County was lined with abundant Texas mock-orange (Philadelphus texensis var. texensis). This fairly uncommon plant is similar to the canyon mock-orange (P. ernestii), which grows in a few canyons near Boerne. These two species are endemic to the southeastern and southern margin of the Edwards Plateau.
We also saw a few sycamoreleaf snowbells (Styrax platanifloius var. stellatus), a Central Texas endemic that grows near Boerne. The rarer Texas snowbell (S. p. var. texanus) grows only on the western side of the Edwards Plateau.
In Real County we waded up a spring-fed stream that gushed through a steep, narrow, travertine-coated canyon. Here the banks were lined with a thicket of spicebush (Lindera benzoin), the largest and densest spicebush growth that the botanists had ever seen. Not surprisingly, a few of the large black spicebush swallowtail butterflies fluttered just above our heads.
Near that site were several watery motts of chatterbox orchids (Epipactis gigantea). This large terrestrial orchid is found in wet limestone canyons across the southern Hill Country, commonly growing among maidenhair and shield ferns. We were too late in the year to see their inch-wide flowers of yellow-green petals and sepals streaked with brownish purple.
Many other not-so-common and endemic plants also are found almost exclusively in the wet limestone canyons that wind through remote areas of the Hill Country. It is gratifying to know that increasingly more landowners are seeking to protect these endangered environments.
Although most of the spring-fed canyons are inaccessible to the casual visitor, there are public areas where these special habitats can be enjoyed by the public. A prime example is Lost Maples State Natural Area, which has perhaps the largest variety of native plants found in the wet canyons of the Hill Country.
