Glad You Asked: How is the UGS Helping Manage Invasive Phragmites?
by Becka Downard and UGS Staff
UGS Wetlands Program Manager and wetlands ecologist Becka Downard holds native phragmites (left side of photo) and invasive phragmites (right side of photo).
Phragmites, pronounced “frag-my-tees,” is a tall, conspicuous perennial wetland grass with a single hollow and stiff vertical stem and distinctive bushy, feathery plumes of flowers and seed heads. There are four subspecies of phragmites and it is among the most widely distributed flowering plants in world. Historically, it has been used in Europe, Africa, and the Middle East for roof thatching, fencing (phragma is Greek for fence), and paper production, among many other purposes. Utah has a native variety of phragmites (Phragmites australis subspecies americanus) that local tribes utilized for building structures and making woven mats and baskets, ropes and twine, sandals, arrow shafts, musical instruments like flutes and whistles, and bird snares. They also used stems for tobacco and herb pipes, and parts of the plant for medicine. The entire plant is edible—young shoots and roots, seeds, and sugar from the stems provide a year-round resource.
Phragmites have been a beneficial plant for humans, however, the introduction of the Eurasian subspecies of phragmites (Phragmites australis subspecies australis) is becoming increasingly problematic in Utah. This exotic plant likely reached the coast of North America over two hundred years ago and has since extended its range across the continent along roads, water ways, and lakeshores. In the last few decades, this invasive phragmites has aggressively expanded throughout Utah, reducing habitat for native plants (including native phragmites) and animals and consuming limited groundwater resources.
The Eurasian subspecies of phragmites (hereafter called invasive phragmites) is legally known as a Class III Noxious Weed in Utah that must be contained to prevent its spread. The plant thrives in disturbed, marginal, and barren grounds and it can quickly move into areas after flooding, fire, native vegetation removal, or nutrient loading. It is remarkably versatile, growing in seasonally dry, submerged, or saturated soil. Invasive phragmites flourish in acidic or alkaline soil, slightly salty or freshwater, and oxygenated or oxygen-free (anoxic) water.
Invasive phragmites have an immense impact on our wetlands. The tightly packed stems of the plant, with upwards of 60 stems per square yard, crowd and shade out other plants. The plant also releases toxins into the soil that can prevent seedlings of other species from taking hold. Invasive phragmites affect the hydrology of wetlands, stagnating water and providing an ideal breeding ground for mosquitoes. Studies suggest it uses twice as much or more water than native wetland vegetation. Currently the Utah Geological Survey (UGS) is partnering with the Utah Division of Water Resources to measure evapotranspiration in phragmites-invaded marshes to quantify how much the invasive grass is using and how much water can be conserved through eradication.
Invasive phragmites grow from seeds (up to 2,000 seeds from one seed head) or spread via runners, a process called cloning, to create a robust, dense network of rhizomes (horizontal underground stems) and stolons (above ground stems). The majority of phragmites biomass is an underground network of rhizomes and roots. These amass over time, trapping sediment—up to several pounds of sediment per square yard per year—which gradually raises the ground elevation of wetlands, moving the ground surface farther from the water table. Invasive phragmites reduces habitat for most fish, migratory and resident shorebirds, waterfowl, and marsh birds. It clogs canals and culverts, and limits access for recreational opportunities such as fishing, hunting, and swimming. Stands of invasive phragmites can also present an extreme fire hazard—at the end of the growing season the stalks and leaves die off, dry out, and will swiftly burn if ignited.
The first invasive phragmites specimen in Utah was collected at the Jordan River near Camp Williams and officially identified as the invasive subspecies in 1993. Researchers believe that the invasive phragmites population around Great Salt Lake surged during and after the 1980s wet years, when prolonged flooding inundated vast areas of wetlands along the east side of the lake. The lake then receded, leaving behind barren lands that were ripe for a phragmites invasion. Its colonization of the eastern side of Great Salt Lake also coincided with urbanization and population growth, which resulted in a several-fold increase of two key plant nutrients: phosphorus and nitrogen. By 2011, invasive phragmites occupied at least 23,000 acres around Great Salt Lake. Today it represents more than 90% of the phragmites in the Great Salt Lake watershed, greatly outcompeting the native species.
Because invasive phragmites is so robust, both above- and below-ground, successful treatment requires a multi-year, multi-pronged approach (i.e., integrated invasive species management). The first step is to treat phragmites during late summer with herbicide approved for aquatic ecosystems. The plant must be healthy so that herbicides can translocate to the roots, ensuring that the grass and its root system is killed. Once dead, treatments such as mowing, trampling, cattle grazing, or controlled burns are used to remove the above-ground material so that native wetland plants can thrive. The herbicide and physical treatment combo is repeated until the phragmites is entirely removed, after which native vegetation (including native phragmites) is planted to prevent further invasion and improve habitat.
In the last 20 years, three-quarters of invasive phragmites coverage has been eliminated on Utah Lake and tens of thousands of acres eliminated from around Great Salt Lake. The Department of Natural Resources has invested significant time and money in removing phragmites around Great Salt Lake, treating more than 6,000 acres in 2022 alone. In 2024 the state allocated $1.4 million for invasive species management on sovereign lands.
Although Utah has turned a corner in phragmites treatment, stopping expansion and restoring significant acreage of invaded marshes, the work has only just begun. Effective follow up treatment requires up-to-date mapping showing where phragmites is growing during the current year, a challenge given the size of waterfowl management areas. To help identify these areas of new growth, the UGS, in partnership with the Utah Division of Forestry, Fire & State Lands and the U.S. Fish and Wildlife Service, is developing computer models that can use drone and satellite imagery to map phragmites in a 30,000-acre wildlife management area to direct large-scale phragmites treatments each season (see Survey Notes, v. 57, no. 2).
Utah Division of Forestry, Fire & State Lands
Forestry Fire and State Lands (FFSL, a division of the Utah Dept. of Natural Resources) is the executive management authority of approximately 1.5 million acres of lakebed that includes critical wetlands of hemispheric importance. Invasive vegetation is actively managed by FFSL to enhance and maintain the crucial functions of these wetlands. Visit FFSL’s StoryMap of the Phragmites removal success at Utah Lake.
