Conservation Matters July 2015

The Texas Land, Water and Wildlife Connection

IRNR drought study continues putting popular plants to the test

By Leslie Lee

IRNR drought study continues putting popular plants to the test

Blue plumbago, Hinckley’s yellow columbine and purple fountain grass are just a few of the species among the 1,600 plants being monitored by researchers in a drought survivability study in San Antonio. More than 30 volunteers planted the landscape plants in a drought simulator in February as part of the water-minded horticultural experiment.

Texas A&M Institute of Renewable Natural Resources (IRNR) and Texas A&M AgriLife Research personnel are conducting the study, which is funded by the San Antonio Water System (SAWS), San Antonio River Authority (SARA), and cities of Austin and Georgetown.

The study is assessing the drought tolerance of 100 popular Central Texas ornamental plant species using a 5,000 square-foot drought simulator bed located on San Antonio’s south side. Another 500 plants were planted at a similar Georgetown drought simulator later in February. Both structures mimic drought by quickly moving to cover the beds when rain begins.

The plants at both locations were then irrigated for a four-month establishment period. All of the beds were also equally covered with mulch, which helps conserve moisture, lower soil temperatures and reduce weed growth.

“All of the plants received the same amount of irrigation for four months so that they could grow and develop before being subjected to drought treatments,” said Forrest Cobb, IRNR student technician. “Generally, more established plants are more resilient to drought stress.”

After that, each simulator’s bed was divided into four experimental plots, which have been irrigated at one of four treatments: 0 percent, 20 percent, 40 percent or 60 percent of reference evapotranspiration. The plants were continuously monitored during this time, and the data was gathered to determine the plants’ minimum irrigation requirements.

In June, project staff began collecting preliminary data. Final data will be collected in September.

“The study is too early to show any major results; however, we expect some plants to perform well with less or no water, whereas some will progressively wilt,” said Amy Truong, extension assistant for IRNR and project lead. “The results will help shape landscaping guidelines in Texas.”

Ornamental irrigation can make up as much as 30-60 percent of home water use, so more accurate information on plant water requirements will benefit future water conservation efforts and education, Truong said.

Local volunteers have helped throughout the project with weeding, mulching and maintaining the study beds, Truong said.

“We have a group of committed volunteers from the Bexar County Master Gardeners, landscaping industry and the public that helps collect data on a weekly basis,” Truong said. “Their backgrounds vary but our goal is the same: we want to identify plants that are most prepared for drought climates in order to reduce outdoor water use.”

Species being tested include 'Moy Grande' hibiscus, knock out rose, mistflower, Sago palm, purple coneflower and Fanick's summer phlox.

San Antonio residents, central Texas gardeners and others interested in the project can like the study's Facebook page for easy access to updates, plant descriptions, volunteer day announcements and more. For more information, contact Truong at 210.277.0292, ext. 102, or

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