Chapter IID. Seasonal Flora of the Sides of the Outcrop


Several species of Euphorbia (Spurge) grow on the outcrop. Snow-on-the-Prairie (E. bicolor) can be very showy. The flowers are small and green, but the bracts subtending the inflorescences have broad white margins. Be careful of the sap: many species of Euphorbia have irritant sap and this plant seems to be worse than most.

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Flowering Spurge (Euphorbia corollata) has pretty little "flowers." Actually, as in all species of Euphorbia, what looks like a flower is really an entire inflorescence called a cyathium. Each cyathium has a number of male flowers, each consisting of a single stamens, and one female flower. What looks like a row of white petals is in fact a ring of glands and appendages around the rim of the cyathium.

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A third species, E. missurica, looks a little like Flowering Spurge but tends to have all the gland appendages crowded on one side of the cyathium. (Image not yet available.)

Two great plants grow at the foot of the outcrop. White Milkwort (Polygala alba) sends up slender stems topped with conical clusters of small white flowers. This perennial is quite tough and can get to be rather large and woody at the base. It likes full sun and sandy soil.  Up close, the flowers look like tiny orchids.

   

Clammyweed (Polanisia dodecandra) looks a lot like Spiderflower (Cleome) that many people grow in the garden. The two are in fact members of the same family. They share the same form--tall and slender--and the same long, brightly colored stamens. Polanisia is a handsome plant, with its pink flowers and shiny black seeds. If it grows anywhere else locally, we don't know about it.

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The midslope has its own interesting flora.

Growing right out of the cracks in the rock at about midslope we find Texas or Lady Bird's Centaury (Centaurium texense). This plant is named after former first lady Lady Bird Johnson, who loved it and planted it on her ranch. It is very rare in this region. The bright pink flowers look much like Prairie Rose-Gentian (Sabatia campestris) in that they have five bright pink petals, but the plant is smaller in all aspects.

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Also rare in the region is Skeletonplant (Lygodesmia texana). This plant is much more common nearer the Edwards Plateau. The common name describes the nearly leafless stems with their leaves cut into narrow segments. The pale lavender flowers are unusual among local members of the Asteraceae with ligulate heads.


Another interesting composite is Indian Plantain (Arnoglossum plantagineum).  The leaves are broad and appear to have parallel venation (unusual for a dicot).  The flower heads are a pale greenish- or yellowish-white, and they rather look like they've been squeezed from a cake-decorating tip.

   

On the other hand, the heads of Purple Coneflower (Echinacea atrorubens) the standard radiate or daisy type.  This species occurs in a narrow band from southeast Texas to Ardmore, Oklahoma and Topeka, KS.  The ligules of the ray florets (what you would think were the "petals" if you didn't know that this is a group of many tiny flowers) are shorter than to just a bit longer than the width of the head.  (In other species, the ligules are much longer, and often not so intensely colored.)


An interesting plant near the top of the slope was first sighted in the spring of 1998. This is Ground-plum Milkvetch (Astragalus crassicarpus). It has typical purplish pea-family flowers, but the fruit are quite distinctive.  The legumes become plump and juicy with age and are edible.

   

Perhaps the most interesting plant on the outcrop blooms along the slope in September and October. Navasota False Foxglove (Agalinis navasotensis) was described as a new species in 1993. As far as is known, this plant grows only here and in another small area about 100 miles away. It is currently classified as a Category V plant--meaning the plant is on the Watch List compiled by the Texas Organization for Endangered Species. Not enough is known about it to determine if it warrants Endangered Species status.

A. navasotensis, at first glance, is very similar to the locally-common Prairie Agalinis (A. heterophylla) which has been found on the roadside below the outcrop and at the rim of the outcrop, but not on the slope. Prairie Agalinis has broader leaves and flowers that sit right on the stem. A. navasotensis has very narrow, thread-like leaves and pedicels (flower stalks) longer than the calyces and fruit. Both species are hemiparasitic--some of their nourishment is taken from the roots of grasses with which they grow.

NOTE: Please help us protect this rare plant. If you visit the outcrop, please leave the A. navasotensis plants and seeds where they are. They are annuals, so they won't live long after transplanting anyway, and because they are hemiparasites, they require complex conditions for seed germination. (So far, germination has been accomplished only with tissue culture/nutrient medium techniques). If you want to enjoy them for a long time, put a bookmark on this page, or take some photographs for yourself.


CHAPTER III....Permanent (Woody) Plants of the Sides of the Outcrop