Two DYC's (Durned Yellow Composites) found on the outcrop are Black-Eyed Susan and a semi-look alike, Greenthread. Black-Eyed Susan (Rudbeckia hirta) is a common plant in Texas later in the spring. The school bus-yellow rays can be solid or marked with maroon. The foliage is covered with stiff, somewhat raspy hairs. The leaves are entire.
Greenthread (Thelesperma filfolium) has a head that is very similar to Rudbeckia hirta but has foliage that is nearly glabrous (without hairs). The divisions of the leaves are quite slender and thread-like.
The mint family (Lamiaceae) is also well-represented in the spring. These plants usually have opposite leaves, square stems, and a minty or antiseptic smell.
You will probably smell Rock Hedeoma or Mock Pennyroyal (Hedeoma reverchonii) before you see it. The leaves of this small perennial are pleasantly lemon scented and release their aroma if the plant is brushed or stepped on. The flowers are pale purple and not very showy, but the plants do seem to flower for quite a long period of time. The flowers may be more pink or more blue. Note the hairy calyces with long, bristle-like teeth.
Drummond Skullcap (Scutellaria drummondii) has hand puppet-shaped bluish purple flowers marked with white. The distinctive feature of most species of Scutellaria is the calyx--it is two-lipped and has a concave crest on the upper lip. This crest has been amusingly and aptly described as looking "just like a John Deere tractor seat."
Another mint, Prairie Brazoria, Warnockia scutellarioides (Brazoria scutellarioides), is easily mistaken for Skullcap at first look. The flowers are similar in shape and color and the plants are about the same size. The calyx looks nearly the same, too, except that what looks like a crest is actually calyx teeth swept up and back. This plant also grows on the summit of the outcrop, with shade-dwelling plants much larger than their cousins in full sun.
A couple members of the Scrophulariaceae are conspicuous on the outcrop in spring. Texas Paintbrush (Castilleja indivisa), while not abundant, is certainly showy. The bright red-orange bracts hide the tubular green flowers almost completely. Look for it near the base of the outcrop. Quite a bit of natural variation occurs in paintbrushes. This species ranges from the typical red-orange to yellow and peach.
Cobaea Penstemon (Penstemon cobaea) is found high up on
the slope. It has huge, white or pale lavender-pink flowers that look a
Foxglove. In this part of Texas, this plant is most frequently found on
calcareous outcrops such as this one. The stamens are
dicynamous--two long and two short. The fifth stamen is sterile
and modified into a hairy staminodium.
The flowers of Trailing Ratany (Krameria lanceolata) aren't as showy as those of Paintbrush or Penstemon, but they are interesting up close. A unique shade of purply-maroon, the blossoms look a little like legume flowers and a bit like orchids. The plants are low and trailing, bearing the flowers close to the ground. This is the only member of the Krameriaceae in the local flora--a nice find and another indication of the diversity on this outcrop.
Another inconspicuous plant is the Swanflower (Aristolochia erecta, synonym= A. longiflora). One might say it is so inconspicuous as to be invisible. This plant is the sole food of the larva of the gorgeous Pipevine Swallowtail butterfly, shown on a thistle from another location.
The ferocious-looking black and red caterpillars (with bristles and horns!) devour the foliage, sometimes reducing the plants to leafless nubs.
We've yet to actually see this plant on the outcrop, but the butterflies and caterpillars are a common sight, so we're pretty sure it's there (just nibbled to almost nothing.) The accompanying photo of the strange, pipe-shaped flower was taken at another location.
In contrast, one can hardly take a step on the outcrop without encountering Prairie or Fineleaf Bluets (Hedyotis nigricans). This calf-high plant bears tiny four-petaled pale lavender pink flowers nearly the year around.
This Bluet is quite different from the other Bluets found in this part of Texas--most of them are less than two inches tall.