About

Panicum repens is a species of grass known by many common names, including torpedo grass, creeping panic, panic rampant, couch panicum, wainaku grass, quack grass, dog-tooth grass, and bullet grass. Its exact native range is obscure. Sources suggest that the grass is native to "Africa and/or Asia", "Europe or Australia", "Eurasia", "Australia", "Europe, Asia, and Africa", or other specific regions, including the Mediterranean, and Argentina. It is present in many places as an introduced species and often a noxious weed. It has been called "one of the world's worst weeds."

How to grow it

The grass spreads primarily via its rhizome. It has been noted to grow 1.3 cm (0.51 in) in length per day. The stems and rhizomes also produce tillers. The rhizome can endure drying and flooding. Dry or wet conditions may reduce the number of shoots produced by the rhizome, but they do not kill it. The rhizome can disperse when parts of it break off and drop onto the substrate elsewhere, anchoring and putting up new shoots. The plant survives and sprouts after herbicide application, grazing, cutting, plowing or disking, and burning. The grass rarely reproduces by seed. It has been noted to reproduce by seed in Portugal, but does not do so in the United States, and it was described as "incapable of fruiting" in Japan. Seeds are sometimes observed but they are apparently rarely viable, with many studies describing zero germination.

The grass has been widely planted as forage for cattle because it is so hardy, withstanding grazing and trampling, and it can be made into hay. However, it is not one of the more palatable or nutritious grasses.

Where it grows

This grass grows throughout the world in tropical and subtropical areas. It was introduced to the United States in seed for forage grasses and probably in ballast water from ships. It was also imported by the United States Department of Agriculture to grow as a forage grass for cattle. It was deliberately planted throughout South Florida and it easily escaped cultivation, eventually becoming "one of the most serious weeds in Florida," spreading to more than 70% of the waterways in the state. In Lake Okeechobee, it has invaded more than 16,000 acres of marsh. It displaces native plants, growing colonially in thick, monotypic stands. Dense mats or stands of the grass cause hypoxia in the water. Torpedograss management in flood-control systems costs an estimated US$2 million per year.

Other Panicum plants

Bitter panicgrass · Panicum australiense · Witchgrass · Kleingrass · Australian millet · Fall panicgrass · Hairy Panic Grass · Faurie's panicgrass · Wiry panicgrass · Panicum gymnocarpon · Hall's panicgrass · Havard's panicgrass