By Bill Ward
Published in The Boerne Star on June 16, 2006
Some of the prettiest native-plant gardens I’ve seen occur naturally within narrow limestone canyons across the southern Edwards Plateau.
As good native-plant gardens should, these canyon gardens come with water features, mostly springs and small waterfalls.
The canyon gardens feature endemic plants (i.e., plants that grow only in a given area). Jason Singhurst, TP&W botanist and specialist on the flora of this area, told me that the Texas Hill Country has an unusually high number of endemic species. There are more endemics in the Hill Country alone than there are in most entire states.
Floral diversity of the canyons is related to the fact that Central Texas is an area of overlap of the eastern and western plant regimes of the US.
Over time, apparently, unique species have evolved to occupy the special ecological niches of the spring-fed canyons. Some of these endemic plants are related the eastern flora and some to the western flora.
During the spring the canyon gardens are brightened by clumps of yellow-blooming Lindheimer’s rockdaisy (Perityle lindheimeri var. lindheimeri).
This composite is endemic to the southern Edwards Plateau. including the Boerne area. Lindheimer’s rockdaisy often hangs from cracks and crannies on vertical canyon walls where little else can grow.
Another spring bloomer on steep limestone walls is the mock-orange with little four petalled white flowers and tiny ovate to lanceolate leaves.
The native mock-orange bush is a miniature version of the Asian mock-orange that has long been cultivated in American gardens. The canyon mock-orange (Philadelphus ernestii) is abundant in canyons of Cibolo Creek southeast of Boerne.
This species grows in five counties from Travis to Bandera. A very similar species, the Texas mock-orange (P. texensis var. texensis), is found only in canyons of Bandera, Real, Uvalde, and Edwards Counties. Some canyon gardens along the southern part of the Edwards Plateau have bushes and small trees of sycamore-leaf snowbell (Styrax platanifloius var. stellatus).
During the spring this snowbell puts on small white bell-shaped flowers with bright yellow anthers. The blooms generally are in small clusters that hang straight down. This endemic species grows near Boerne.
The similar, but rarer Texas snowbell (S. p. var. texanus) grows only on the western side of the Edwards Plateau.
In late spring many canyon gardens include the tall red-flowering scarlet penstemon (Penstemon triflorus). This species grows in southern and western parts of the Edwards Plateau.
In early spring the rosette of the scarlet penstemon is easy for me to confuse with the rosette of the big red sage (Salvia penstemonoides). Big red sage, which blooms all summer, is known in only a few canyon gardens of Kendall, Bandera, and Real Counties.
The largest population of big red sage is in a canyon of Cibolo Creek southeast of Boerne.
Some particularly watery bars and banks in canyon gardens along the southern margin of the Edwards Plateau support chatterbox orchids (Epipactis gigantea).
This large terrestrial orchid is found mostly in wet limestone canyons across the southern Hill Country, but also is found in other spots scattered around Texas. Commonly it grows among maidenhair and shield ferns.
From March to August this orchid may have inch-wide flowers of yellow-green petals and sepaIs streaked with brownish purple.
Typically, the 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), some of which are endemic to the Hill Country. Commonly there are smaller patches of lip ferns (Cheilanthes sp.), two cliffbrake ferns (Pellaea ovata and P. atropurpurea), and Mexican anemia fern (Anemia mexicana).
As far as I know, few ferns are strictly Hill Country endemics, one being a species of lip fern (Cheilanthes leucopoda) that occurs on the western margin of the Edwards Plateau.
Although most of the garden of the wet limestone canyons are on private land, inaccessible to the casual visitor, there are public areas where these special plant assemblages 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.
