By Cleveland Powell. These two cheery daisies share the same common name, but they grow and thrive in very different soil environments.
San Antonio and Bexar County sit at a wonderful convergence of ecoregions — geographic areas with their own distinct flora and fauna.
Plants are obviously influenced by local soil type and the different kinds of soil in our region also broadly define the local ecoregions. Bexar County has three significant soil groups: rocky clay soils of the north and Edwards Plateau, deep clay soils of the Blackland Prairie in the south and east, and deep sands further south and east.
Both thin-clay and sandy soils present significant challenges for plants and the strategies that work in one soil type don’t necessarily work in the other. That inspired me to write a series of articles to tell a tale of two plants each time.
Up first are two cheery daisies: Tetragonotheca texana and Tetragonotheca repanda.
One grows in northern Bexar County clay soil and the other in the sandy soils of south Bexar County. Both plants often go by the same common name of squarebud daisy. So, to avoid confusion I’ll refer to T. texana as squarebud daisy and T. repanda as showy nerve-ray.
As the common name implies, the unusual flower buds of both plants have four equal sides and resemble little squares. Squarebud daisy flowers have yellow petals with red centers, while nerve-ray has yellow on yellow flowers. Nerve-ray is a larger, showier plant with bigger flowers, leaves and a beefier stem. But don’t count out squarebud daisy. Where it’s found, few other things will readily grow. I often see it happily sprouting out of bare rock, a welcome respite for pollinators on a warm May morning.
Of course, both are well adapted to the South Texas climate and can weather heat and drought, blooming from spring until fall when moisture allows.
While the ranges of these plants come very close, they never actually overlap. As a rule, showy nerve-ray only grows in sandy soils, while squarebud daisy will only grow in the thin soils of the Edwards Plateau. Because of these unique soil and climate requirements, both plants are only found in Texas and adjoining regions of Mexico. Bexar County is one of only a couple of counties in Texas where both plants have been recorded!
You’re not likely to find either of these plants in a local nursery, but wild plants like these highlight how unique San Antonio really is.
Keep an eye out next month for the next tale of two plants.
Cleveland Powell is a conservation planner for SAWS. He is enthusiastic about grass taxonomy and milkweed propagation. In his free time, Powell enjoys hiking around area parks in search of intriguing bugs, birds and plants.
