Panicum repens, commonly known as torpedo grass, is a fast-growing perennial grass that spreads by rhizomes. It grows on the shores of lakes, ponds, and open, moist sandy beaches.
It not only flourishes on wet organic soil but can also grow on high land in a drought environment.
Scientific Classification
- Domain: Eukaryota
- Kingdom: Plantae
- Phylum: Spermatophyta
- Subphylum: Angiospermae
- Class: Monocotyledonae
- Order: Cyperales
- Family: Poaceae
- Genus: Panicum
- Species: Panicum repens
- Common Names: bullet grass, creeping panic, couch panicum, dogtooth grass, torpedo grass, quack grass, wainaku grass, Victoria grass.
Nativity and Distribution
It is thought to be native to the tropical and subtropical regions of Africa, Asia, and Europe.
It is also native to Eurasia and has spread throughout the tropics and subtropics of both hemispheres. It is now widely distributed throughout the world.
Physical Appearance
- Leaves: Leaf sheaths are hairy, and leaf blades are rigid, line-like, flat, or folded, often with a whitish or waxy surface.
- Flowers: It has panicle-type inflorescence, which is 3-9 inches long.
- Fruits: They are lanceolate, straw-coloured caryopses.
- Seeds: They are white and smooth.
- Roots: Fibrous root system.
The flowering stems are erect and are up to 0.8m tall. Consisting of only sheaths, the lower stems may lack leaf blades. The leaves of the upper stem consist of sheaths and blades. These blades are relatively short, folded, and from 2 to 5mm wide.
Inflorescences are open, loose terminal panicles with bristling or ascending branches. Spikelets are about 2.55mm long.
Life Cycle/Reproduction/Dispersal
- Life Cycle: Perennial.
- Seed: Seed/spore propagated, vegetatively propagated.
- Climate: Thrives in moist habitats.
- Dispersal: Seed may be dispersed by human activity or water.
It produces seeds with little to no viability. Primarily it spreads vegetatively through rhizomes and stem fragments, which can form new plants.
New buds tend to be produced along the entire length of the rhizome, which then form into aerial stems.
Impact on Farms and Environment
Torpedo grass invasion tends to be problematic in agricultural systems, which include tea, sugarcane, cotton, rubber, cacao, coconut, citrus, and rice plantations. It also tends to be problematic along canal banks, roadsides, and pastures.
When this invasion occurs around water bodies, it may interfere with flood control, navigation, irrigation, and recreation. Invasive torpedo grass populations are also suggested to displace native vegetation.
It may also affect ecosystem processes in water channels.
Control
It can be difficult and expensive to control. Plants do possess many dormant buds connected with immense rhizomes and can sprout from deep in the soil.
Plants sprout following rhizome disjunct or destruction of vegetation that is above ground. Treatment for several years is needed to control torpedo grass.
Prevention should be part of the plan. The spread of rhizomes can be controlled by limiting populations near waterways, proper cleaning of machinery such as lawnmowers, and only accepting materials like hay, mulch, and soil from certified sources.
Cultural Control
The presence of other vegetation may limit the establishment of torpedo grass.
Physical or Mechanical Control
Not all mechanical methods may be applicable in the control of torpedo grass. Tillage, for instance, has the potential to fragment rhizomes and stimulate sprouting.
Though continuous tillage could provide control, but is impractical in natural areas.
Cross ploughing and deeply burying rhizomes is suggested and it may reduce sprouting after treatment.
One effective method of controlling small patches of torpedo grass is digging though it is difficult to remove all rhizomes. It may result in the scattering of rhizome fragments, which is inefficient and expensive.
Mowing, when done repeatedly, is also another effective method as it limits the development of new rhizomes, though it doesn’t ultimately prevent regeneration.
Flooding or maintaining deep water could limit torpedo grass growth and establishment, but frequent flooding could affect other plants.
Chemical Control
No herbicide can selectively control torpedo glass. Two herbicides that can be used are glyphosate and imazapyr.
Glyphosate kills lawn grass and other plants. Imazapyr is also effective, but it kills other plants and has a residual effect in the soil that can harm trees and shrubs.
Lead Editor for Insight Weeds.