Out of all of the invasive types of weeds that can be found in lawns, flowerbeds, or even in waterways, Panicum repens, or more commonly known as torpedo grass, is the most persistent and resilient. Often considered one of the world’s worst weeds, it’s difficult to remove and unsightly with its scraggly, long appearance. Torpedo grass gets its name from its large, pointed, branching, thick rhizomes that creep along the ground or float in marshy water. Torpedo grass is typically found throughout the world in tropical or subtropical areas and can form fast-spreading, thick, dense mats that are hard to eradicate. It can alternatively be called bullet grass, coastal Bermuda grass, couch panicum, creeping panic, dogtooth grass, panic rampant, and quack grass.
Torpedo grass is thought to have European, Asian, Australian, or African roots and was introduced to the southeastern United States in the early to mid-1800s. In the United States, the weed was deliberately planted as forage grass for cattle and livestock, but it quickly grew out of hand as it spread into many waterways. It was then found that torpedo grass wasn’t as an effective grass for cattle and better alternatives have been used since. Torpedo grass likes to grow in fresh water and salt marshes, wetland habitats, mud flats, tide pools, bogs, and lakesides, but can easily move to ditches or canals. Since the weed can’t handle cold weather, it usually isn’t found above subtropical latitudes and dies after the first frost. In the United States, torpedo grass is most prevalent in southeastern locations like Texas or Florida. In Florida, the weed occurs in 75% of its counties and occupies thousands of acres of marsh. In Mississippi, torpedo grass has been considered for being listed as a noxious weed. Overall, it doesn’t provide habitat quality compared to the native plants it displaces and has even cost the United States 2 million dollars annually in management in flood control systems.
Although torpedo grass is recommended for shoreline stabilization and to be used in areas that go through periods of drought, it more often causes a myriad of issues for homeowners and anyone with a lawn or landscape. The thick mats take over native plants, causing loss of biodiversity, and can deplete oxygen in any water systems they reside in. In moderate amounts, torpedo grass can be a resource for birds and mammals. For instance, muskrats, nutria, rabbits, and other rodents graze upon torpedo grass. Submerged torpedo grass, like other aquatic plants, can provide a habitat for micro and macro invertebrates that are used as food by fish, amphibians, reptiles, ducks, and other wildlife species. When the plant dies, their decomposition provides food (detritus) for aquatic invertebrates. It can be hard to keep the plant under control, especially in small quantities in one location because its rhizomes creep and spread, so limiting the weed to one area can be next to impossible. For this reason, most people try to get rid of the weed at all costs, especially if the weed is found on their property.
The first step to managing torpedo grass is monitoring the situation and estimating the degree of growth and spread. The key with torpedo grass is to make frequent and diligent efforts in removal because the weed is so difficult to completely get rid of, especially in one attempt. Herbicides provide one of the best solutions to treating and managing this pesky weed, though routine treatment will most likely be necessary. A powerful herbicide that is considered the most effective against torpedo grass is a glyphosphate, although it will kill lawn grass and any other surrounding plants. Be careful to avoid getting herbicides into waterways because this can cause pollution. After repeated treatments with a herbicide, re-sodding the section can prevent future big time spreads of the weed.
Some other methods of removal include solarization, which is covering a larger area of lawn with clear plastic for a month or two during the summer season, allowing the sun to bake anything underneath. Another method is burning during the winter season and then spraying the weed with herbicide when it begins to sprout. Pulling and digging is a manual technique that isn’t always effective since parts of the broken plant can possibly spread and sprout once again. To keep an existing lawn healthy and to help prevent large-scale infestations, improving drainage and soil quality is usually recommended. Replacing disturbed soil with sod, lawn grass, or naturalized beds in burnt or tilled areas is also a great way to prevent future infestations.
Though it’s a pesky and tough weed, with some effort and patience torpedo grass can be managed to an extent.
Day, J. (2010). How to Control Torpedo Grass in Your Lawn | Today’s Homeowner. Retrieved March 18, 2016, from http://www.todayshomeowner.com/how-to-control-torpedo-grass-in-your-lawn/
Gill, D. (2012, July 19). Go On the Offensive Against Torpedo Grass. Retrieved March 18, 2016, from http://www.nola.com/homegarden/index.ssf/2012/07/go_on_the_offensive_against_to.html
IPAMS – Species Information – Panicum repens – Torpedo grass. (n.d.). Retrieved March 18, 2016, from https://www.gri.msstate.edu/ipams/species.php?SName=Panicum repens
Panicum repens. (n.d.). Retrieved March 18, 2016, from https://en.wikipedia.org/wiki/Panicum_repens