We use the word "thorn" very generically to refer to any sharp pointy part of a plant. However, to be technically correct, there are three different types of sharp pointy things:
- Prickles are modified epidermal tissue. The epidermis is the surface layer of the stem. Prickles are found on many plants in the Rosaceae (Rose) Family, as well as other plants such as Greenbrier vine.
- Spines are modified leaf tissue. The sharp pointy things on cacti are spines. The sharp tips of Agarita leaves and the sharp projections along the margin of Sotol leaves are also spines.
- Then there are the true thorns. Thorns are modified branch tissue. They are essentially branches with sharp pointed tips. Numerous trees and shrubs have true thorns.
This is going to be a series of posts. Probably the best place to begin is with the Bluewood Condalia (Condalia hookeri). This Condalia generally grows as an understory shrub in wooded areas of the Texas Hill Country and to the south in the open brush throughout the South Texas Brush Country.
The leaves of Bluewood Condalia grow on twigs with a very sharp terminal thorn. This is by far one of the best examples demonstrating that thorns are in fact modified branches:
Lote-bush Condalia (Ziziphus obtusifolia) looks very similar to Bluewood Condalia and the two are easily confused. Their ranges overlap in Texas. While they are not in the same Genus, they are both in the Rhamnaceae (Buckthorn) Family. Both of these shrubs have leaves on twigs with terminal thorns. The Lotebush, as it is often called, has twigs with leaves as well as bare twigs both with terminal thorns.
This set of photographs was taken along the Yanaguana Nature Trail at Mission San Juan in the San Antonio Missions National Historical Park on Monday, October 28, 2013.
I have to give credit to Dr. Floyd Waller, my botanist friend and mentor, for the original inspiration for this series of posts.
Of course, it's big. It's the Official State Tree of Texas, the Pecan:
This particular pecan tree is so big it didn't all fit in the frame even with an 18 mm wide angle lens. These three photos only give an idea of the height of this tree and the width of its canopy. There really isn't any true sense of the diameter of the trunk, either. Pecans grow very well in the riparian woods here, so it is difficult to estimate the age of the tree by its size, however I think it is safe to say this is a fairly old pecan tree.
This set of photographs was taken along the Yanaguana Nature Trail at Mission San Juan in the San Antonio Missions National Historical Park on Monday, October 28, 2013.
The bright red flowers of Turk's Cap (Malvaviscus arboreus var. drummondii) command attention as one walks by them along the trail, but there is so much more to this plant than just the attractive flower:
Turk's cap is a fairly common wildflower in the eastern Texas Hill Country, throughout southeast Texas and the southeastern United States. It is being increasingly recognized as a valuable native landscape plant.
This mallow grows exceptionally well in even relatively deep shade, but prefers partial sun and will tolerate full sun. It prefers moist soil, but is also surprisingly drought tolerant. Birds, especially hummingbirds, butterflies and other pollinator insects are drawn to the flowers.
The flowers, the young leaves and the ripe fruit are all edible by people. The flowers are frequently added to a green salad and other dishes for both color and a sweet accent. The young leaves can be cooked the same way any other green leafy vegetable is prepared. The ripe fruit is called manzanilla and, as the name implies, has an apple flavor. Manzanilla, meaning "little apple" in Spanish, is another common name for this plant.
This set of photographs was taken along the Yanaguana Nature Trail at Mission San Juan in the San Antonio Missions National Historical Park on Monday, October 28, 2013.
As I walked along the trail beside the San Antonio River, I happened to look up between two trees. About ten feet or so off the ground, this large orb weaver spider appeared to be suspended in mid-air. Its web was invisible against the bright light of the sky:
Given the lack of detail due to the bright backlight of the sky, I really can't identify the Genus, much less the species of this spider. The large orb weavers in the Family Araneidae are very common in South Texas particularly in the Fall.
This set of photographs was taken along the Yanaguana Nature Trail at Mission San Juan in the San Antonio Missions National Historical Park on Thursday, October 17, 2013.
The Green Anole (Anolis carolinensis) is just as apt to be brown as it is green, or some mix of color in between. It has the ability to change its color based on multiple factors. This is another arboreal dweller, preferring to hunt for insects and spiders in the foliage of trees and shrubs. They also prefer to live in moist wooded areas such as riparian woodlands.
These lizards can be found throughout the southeastern United States with Bexar County located near the western edge of its range:
This set of photographs was taken along the Yanaguana Nature Trail at Mission San Juan in the San Antonio Missions National Historical Park on Monday, October 28, 2013.
I have had the opportunity this past month to spend a great deal of time studying the 25 or so acres of the Yanaguana Nature Trail at Mission San Juan and sharing what I have learned about this remarkable natural habitat with high school environmental science students. The more I learn about this remnant riparian woods, the more I am in awe of the biodiversity located here.
This is the land located between Mission San Juan and the remnant channel of the San Antonio River. Ecologically, it is located within the convergence of the Post Oak Savanna ecoregion to the northeast and east and the Tamaulipan Plains, also known as the South Texas Brush Country, to the south and southwest. There is an interesting mix of flora and fauna from both of these ecoregions.
Over the coming week or so the posts here on While on a Walk will go into more detail regarding this fascinating habitat.
The American Beautyberry is as good a beginning as any for this series. Callicarpa americana is in the Verbenaceae (Verbena) Family. It is most commonly found in riparian woodlands and other moist wooded areas of the Post Oak Savanna ecoregion and the woods of Southeast Texas and the Southeastern United States.
It is fairly easy to recognize this plant when it has ripe fruit, as the red to purple berries grow in dense clusters around the leaf axils:
The berries are highly astringent, but berry eating birds are so highly attracted to them, they will fight over territory around these shrubs when they bear ripe fruit.
This set of photographs was taken along the Yanaguana Nature Trail at Mission San Juan in the San Antonio Missions National Historical Park on Monday, October 28, 2013.
Bexar County is in a unique and critical location along the migratory bird North American Central Flyway. The riparian habitats along the San Antonio River and its numerous tributaries here provide the necessary water and fuel sources for these birds. This is one of the first stops in the Spring as they arrive from their flight north across the Gulf of Mexico and the last stop in the Fall before they begin their flight south across the Gulf.
As I mentioned briefly in "A Distinctive Bark," many of the migratory birds, particularly the song birds such as the thrushes and sparrows, rely on the fruit of the Sugar Hackberry trees to provide the necessary energy reserve for their fall migration. There are a number of species of birds that primarily eat insects and other small invertebrates during the nesting season that eat berries and seeds during their migration. The Hackberry fruit are very high in sugar and essential oils and the seeds rich in protein:
Of course, birds aren't the only animals that rely on these berries to help them survive the fall and winter. Numerous mammals, such as possums, raccoons and deer, find them quite appealing. For the most part, people stopped eating these berries after the invention of agriculture, but Hackberry fruit was one of the staples for hunting and gathering societies living where these trees were abundant.
This set of photographs was taken along the Yanaguana Nature Trail at Mission San Juan in the San Antonio Missions National Historical Park on Thursday, October 17, 2013.
