Panicum repens

Panicum repens
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Monocots
(unranked):	Commelinids
Order:	Poales
Family:	Poaceae
Genus:	Panicum
Species:	P. repens
Binomial name
Panicum repens L.

Panicum repens is a species of grass known by many common names, including torpedograss, 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, Israel, 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."

This perennial grass spreads via its large, branching rhizomes, which are thick and pointed. The pointed shape of the rhizome tip gives the plant the name torpedograss. The rhizomes creep along the ground or float in water, forming floating mats. They can reach a length of 6 meters (20 ft) and a soil depth of 7 meters (23 ft), and they can form a mat 15 centimeters (5.9 in) thick. The spreading rhizomes sprout repeatedly to form colonies of stems. The stems are 20 to 90 centimeters (7.9 to 35.4 in) tall, sometimes reaching 1 meter (3 ft 3 in). They grow erect or bend down. The leaves are stiff and straight, linear in shape, and flat or folded. They are sometimes white in color and waxy in texture. The inflorescence is a loose panicle of branches bearing small spikelets 2 to 3 millimeters (0.079 to 0.118 in) long.

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 southern 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.

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Wikipedia