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Roadside biodiversity, then and now
In his 1947 classic, “Adventures with a Texas Naturalist,” Roy Bedichek described a roadside experiment.
On a May afternoon, he walked a mile along a Texas highway, recording the species of flowers along the right-of-way. He listed 68.
It gets worse. On the following days, he duplicated his experiment along goat and sheep enclosures. Highway right-of-way: 46. Goat pasture: Eight. Highway: 54. Sheep pasture: A solitary rain lily.
“This flower pops up and out as if it was set on a spring explosive,” Bedichek wrote. “It is one of the few species agile enough to elude the goat or even the sheep and get in its blooming while they are not looking.”
From 1917 to 1948, while Bedichek was criss-crossing Texas as director of the University Interscholastic League, he witnessed the state’s most visible ecological disaster: Overgrazing. The practice of fencing in too much livestock stripped the topsoil from Texas ranchlands, leaving it vulnerable to undesirable, thirsty species like salt cedar and mesquite.
In contrast, the rights-of-way along the state’s new highways appeared to be paragons of biodiversity. In “Adventures,” Bedichek praised the landscape experts of the Texas Department of Transportation who, beginning in 1932, promoted indigenous plants under the criteria: “Safety, Beauty, Utility, Economy.”
Experts still commend TxDot for its propagation of native species. That effort now includes the American-Statesman’s ongoing Lady Bird’s Legacy wildflower campaign.
Last year, 80 percent of the Legacy donations went to purchasing seeds distributed throughout Central Texas by TxDot. Eight percent of the $100,000 raised paid for seed packets for schoolchildren; 12 percent for plantings in parks and other community locations.
“Much of the credit for the spectacular displays of wildflowers along Texas’ roadways can be directly attributed to TxDOT’s distribution and protection of native wildflowers across the state,” confirmed Damon Waitt, senior biologist at the Lady Bird Johnson Wildflower Center.
Some metaphorical weeds grow in this roadside garden, however. Waitt and other experts are concerned with inadvertent introduction of invasive species and the department’s selective use of non-native Bermuda grass seeds.
“The same features that make (Bermuda grass) ideal for roadside revegetation — quick establishment and rapid colonization — also make it a threat to parks, natural areas and wildlands,” Waitt said.
“I’ve never seen Bermuda grass take over native species,” responded Dennis Markwardt, TxDot director of vegetation management, explaining that the department uses this familiar, adaptive species in areas that require low vegetation, and in combination with natives.
Travis Gallo, coordinator of the Invaders of Texas program at the Wildflower Center, focuses his ire and energy on species such as the bastard cabbage, tall yellow flowers that are threatening to crowd out roadside natives, like the ones planted through the Legacy campaign.
“It is spread through contaminated grass seeds when people re-seed an area,” Gallo says. “It is in the mustard family and we all know how small mustard seeds are (biblically small, so to speak). So, the bastard cabbage seeds do not get caught in the screening process as the grass seeds are screened. The actual introduction is unknown, but it is likely that it was introduced in the same fashion, contaminated grass seeds.”
Which means TxDot and other entities maintaining rights-of-way might have unknowingly contributed to the bastard cabbage invasion.
What is to be done? Wildflower Center restoration ecologist Mark Simmons tested a way to artificially increase the density of native wildflowers and therefore reduce the bastard cabbage population.
“This would be a great method for large scale roadsides,” Gallo says. “You could also develop a strategic mowing/weed-eating regimen and reduce the population. It is an annual, so if you knocked back the plant before it goes to seed you would reduce the seed bank. It would take several years of mowing/weed-eating to see results.”
At TxDot, Markwardt’s vegetation department is as dedicated to promoting natives as it was back in 1932, when Bedichek first described the beneficial effects of highway right-of-way management. The economic scale, however, of managing vegetation along thousands of Texas highway miles means runs smack into commercial roadblocks.
“The seed market drives us. And that is driven by cattle producers,” Markwardt says. “But we are working with Texas A&M-Kingsville on commercial seeds from grasses that thrive in South Texas. So far, however, they don’t produce enough to meet our needs.”
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