Biology students from Trinity University returned to the Texas Butterfly Ranch last week to continue battle with invasive species–specifically, Johnson grass. Four students arrived last Friday to take stock of an ongoing experiment that began last April on the banks of the Llano River and will continue through next year. The goal: figure out which methods are most effective in killing Johnson grass.
“We successfully reduced Johnson grass abundance using both grubbing and herbicide,” said biology professor Dr. Kelly Lyons, a restoration ecologist and invasive plant expert who organized the experiment for her students. While it’s too soon to say whether grubbing (physically removing the Johnson grass) or herbicide (aquatic-safe glyphosate) is more effective, preliminary data suggest that where Johnson grass was reduced, biodiversity increased.
“We also found that in these rainy seasons, Goldenrod competes well with Johnson grass, albeit to the exclusion of most other species,” said Dr. Lyons.
That’s good news for migrating Monarch butterflies who use the late season bloomer as a nectar stop as they move through the Texas Funnel each fall on their way to Mexico.
The project began last April as part of Trinity University’s ongoing research funded by the University, Texas Ecolab, and the National Science Foundation. Last spring, a team of students arrived at the ranch to set up plots and gather baseline data on plant density and diversity. Students established four 15- x 2-meter plots were established and applied different forms of Johnson grass control–grubbing, weedwhackjng, and herbicides, in various combinations.
On this visit, Levanya Hospeti, Molly Lenihan, Austin Philippe and Olivia Roybal joined Dr. Lyons to collect data and plant plugs of native Eastern gamagrass, Tripsicum dactyloides, a boisterous grower that Dr. Lyons believes can compete heftily with the rambunctious Johnson grass. Students planted 20 Eastern gamamgrass plugs and will continue monitoring the site over the course of the next year.
Texas Invasives cites Johnson grass as one of the Top 10 Most Noxious weeds in the world. It arrived from the Mediterranean in the 1800s when it was imported as a supplementary foraging crop–even though when stressed, it can produce toxic amounts of hydrocyanic acid that makes it poisonous to livestock. The super aggressive grass spreads through rhizomes and seeds, hogs space and resources, and crowds out natives that provide food, fodder and shelter to local wildlife.
For years we’ve enjoyed lovely stands of Goldenrod and Frosted on the Llano in the fall when the Monarchs pass through. Solidago altissima and Verbesina virginica, beautiful yellow and white late season nectar sources, respectively, serve as important fuel and resting stops for migrating Monarch butterflies and other creatures. But ever since a road project disrupted our stream bank and hauled in uninvited Johnson grass, we’ve been fighting the battle to win back our native nectar plants.
Dr. Lyons thinks that the Goldenrod and Eastern gamagrass, a lovely, large bunchgrass related to corn that grows two – 10-feet tall, are up to the task.
“The species is already present in high abundance and provides high quality habitat,” said Dr. Lyons, adding that Eastern gamagrass also works as a great soil stabilizer in river ecosystems. “Restoration ecologists often refer to it as ‘riparian rebar’ since its rhizomes are even more substantial than Johnson grass,” she said.
So the battle continues. No surprise that we’re rooting–pardon the pun–for Eastern gamagrass. It offers multiple benefits to our local creatures, including service as a host plant to the Bunchgrass skipper. It also appears to be a steady companion to our Llano River Swamp milkweed, Asclepias incarnata, host plant to Monarch butterflies. Tall mounds of Eastern gamagrass already occur naturally all along the Llano, providing shade for late season milkweed from harsh summer sun.
We spend a lot of time and energy talking about restoring native milkweeds and other pollinator plants to the prairies that we’ve lost. It’s equally important to manage and combat the advances of invasive species that infect our wildscapes. Johnson grass is just one interloper. Check out the Texas Invasives website for more information. We’ll keep you posted on the progress of the project.
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