The San Antonio River’s South Channel is finally getting some much-needed attention. In the past three months, the 1.5-mile stretch of the river that winds through the historic King William neighborhood from West Nueva Street to South Alamo, has seen the removal of invasive species, the first planting of three pollinator gardens, and a long overdue clean-up of rotting detritus that had occupied the river for almost a year. The South Channel has also become a study site for citizen scientists and biology students at Trinity University.

Following a Feb. 23 Rivard Report story that detailed the South Channel’s neglect, the City of San Antonio redirected resources to address these issues.

The most challenging task was removing dense stands of elephant ears, Colocasia esculenta, an invasive aquatic plant that had colonized three of five aquatic planters on the banks of the South Channel. The plant is listed as a noxious weed by the Texas Department of Agriculture and as a prohibited exotic species by the Texas Parks and Wildlife Department. Its boisterous growth and easy colonization habits have made it an expensive threat to the downstream $271 million riparian restoration undertaken by the San Antonio River Authority (SARA).

To address the elephant ears, the City contracted with Southwest Aquatic Services, a waterway management specialist based in Altair, Texas, licensed to apply aquatic herbicides. The first round of two herbicides and a surfactant – which makes the herbicide stick to the leaves of the plant – was applied on May 4. Another application was administered on May 24.  The third round will take place in the next week or two, weather permitting.

Andrew Labay, the contractor who applied the herbicides, said he thought the project was successful. “Of course, there’s always a chance that a few plants could sprout from rootstock, seeds, and corms that did not come in contact with the herbicide,” said Labay by phone. “All we can do is monitor and spot treat as they come up to keep them from coming back. Hopefully, we were successful in getting all of them.” Recent heavy rains assisted in the process, helping to clear out dead plant material, Labay said.

Elephant ears
Parts of elephant ears, decimated from aquatic herbicides, float downstream on May 27. Photo by Monika Maeckle.

A kayak tour on May 27 revealed many floating elephant ear corms and roots moving downstream with a current agitated by recent rains. Steven Schauer, spokesman for SARA, which oversees the Mission Reach riparian restoration and actively targets the plant for removal, was not concerned that the pesky invasive might take up residence downstream.

“Our maintenance staff is confident that the fragments that may have broken off during the herbicide treatment should be dead,” Schauer said via email.

Just south of the Nueva Street Bridge on the South Channel’s west bank, the first of three pollinator gardens were installed in March. City crews removed turf grass, installed metal edging, and planted dozens of milkweeds and salvias, Lantana, and Esperanza. Monarch butterflies were already laying eggs on the pollinator patch two weeks following its installation.

Since, the Monarch Larvae Monitoring Project, a citizen science initiative organized by the University of Minnesota and staffed by local volunteers, has made the South Channel pollinator patch one of its monitoring sites. Longtime volunteer Mobi Warren said she checked the new site for Monarch butterfly eggs, larvae, and adults this spring and plans to return in the fall.

monarch nueva st. bridge
A male Monarch butterfly takes off from Buddleia at the new Nueva Street Bridge pollinator patch on the South Channel. Photo by Juan Guerra for the City of San Antonio. Credit: Juan Guerra / City of San Antonio

Trinity University students have also visited the site as part of associate professor Kelly Lyons‘ Intro to Biology class. Lyons asked students to monitor milkweed and Monarchs at the Nueva Street patch among other sites and required them to base their final paper on the data they collected.

“The Monarch butterfly system is ideal for exposing students to critical conservation issues, hands-on approaches to studying the natural system, and the scientific process,” Lyons said.

Trinity milkweed south channel
Trinity University students monitor milkweed and Monarchs at the South Channel pollinator patch. Photo courtesy COSA.

Two more pollinator gardens are planned for late summer or early fall: one at the San Antonio River Authority shore line and another at Gate 6 near Blue Star. City staff have purchased 1,000 native Antelope horn milkweed plugs, Asclepias asperula, from citizen science organization Monarch Watch for the gardens. The plants are being tended to at a local nursery until they are large enough to transplant and the harsh summer heat has passed.

The future home of a pollinator garden that the San Antonio River Authority will plant outside its headquarters.  Photo by Scott Ball.
The future home of a pollinator garden that will be planted at the San Antonio River Authority outside their headquarters. Photo by Scott Ball.

The five aquatic planters, three of which served as home to the Elephant ears, will prove to be more challenging than the terrestrial gardens. Aquatic specialist Labay said he was concerned for the structures.

“They should be either shallower or above the water,” he said, adding that the depth of the planters and the reality that a plant’s roots will always have “wet feet” limits the plant selection. “There are different types of wetland plants that do well in moist soil, but not in soil that is permanently submerged,” Labay said. “That really limits the choices.” Labay mentioned that the planters are not quite deep enough to support many aquatic plants. Additionally, not many plants can withstand severe floods like the ones recent heavy rains caused.

Current plans call for the installation of Pickerel weed, Pontederia cordata, an aquatic plant with heart-shaped leaves and spikes topped by a purple flower beloved by bees and butterflies.

Pickerelweed will likely take the place of Elephant ears in the aquatic planters. Photo courtesy of D. Gordon E. Robertson.

Initial reactions to the changes along the South Channel have been more positive than negative. While some residents said they miss the “lushness” of the Elephant ears, others were glad that the South Channel received some love. Several residents who frequent the South Channel said they didn’t especially like the process, but look forward to the outcome which will require patience and rounds of trial and error.

“We think it’s a good thing to restore the river back to its original native habitat,” said Cherise Bell, executive director of the King William Association. “Just like in the restoration of a historic home, you go through an ugly period before you reap the benefits of the restoration.”

Top image: Mike Casey and Peter Grojean paddle a canoe North on the San Antonio River. Photo by Scott Ball. 

Related Stories:

Reimagining the San Antonio River’s South Channel

In Speech and Play, a City Reclaims the San Antonio River’s Mission Reach

NWF Names San Antonio First Monarch Butterfly Champion City

A Day’s Bounty Kayaking the Mission Reach

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Monika Maeckle

San Antonio Report co-founder Monika Maeckle writes about pollinators, native plants, and the ecosystems that sustain them at the Texas Butterfly Ranch website. She is also the founder and director of...