Elephant Grass, scientifically known as Cenchrus purpureus (formerly Pennisetum purpureum), is a rapidly growing perennial grass native to the tropical savannas of Africa. This species is renowned globally for its immense biomass production. This gives it a dual identity: a valuable economic resource when cultivated, and a problematic invasive weed when it escapes managed areas. Understanding this grass requires looking at its physical characteristics, economic importance, mechanisms of spread, and necessary management steps.
Identifying Elephant Grass and Its Agricultural Value
Elephant Grass is a robust, large-statured plant that often grows in dense, bamboo-like clumps or tussocks, reaching heights of 10 to 15 feet. The stems are erect and stout, supporting broad, strap-like leaves that can be several feet long. A defining feature is the terminal flower head, which forms a dense, cylindrical spike, often appearing greenish-tan or purple-tinged, and covered in distinctive long bristles.
This grass, often called Napier Grass, was introduced to many tropical and subtropical regions for specific economic benefits, primarily as an exceptionally productive forage crop for livestock. It is highly valued in cut-and-carry systems for feeding cattle and buffalo due to its high yield and nutrient content. Beyond animal feed, its dense growth makes it effective for erosion control, improving soil fertility, and serving as a windbreak. Its rapid growth and high biomass also position it as a promising crop for biofuel production.
Characteristics That Define Its Invasive Nature
The very traits that make Elephant Grass agriculturally useful are the ones that define its invasive potential when it is not managed. As a perennial, it establishes a deep, persistent presence and has multiple, highly effective methods of reproduction. It spreads aggressively through vegetative means, primarily via short, creeping rhizomes and root crown divisions. Even small fragments left in the soil can quickly resprout into new plants.
This vegetative spread allows the grass to form dense, impenetrable stands that exclude almost all other plant life. Viable seeds are also produced and can be dispersed by wind, water, and by attaching to clothing or vehicles. Once established, its sheer size and rapid growth rate allow it to outcompete native vegetation by monopolizing sunlight and soil resources.
The resulting dense, monocultural growth fundamentally alters the local ecosystem. It prevents the regeneration of native species and can create significant problems in infrastructure, such as blocking flood control systems and reducing water flow in waterways. Furthermore, Elephant Grass recovers exceptionally well after fire, which allows it to quickly re-establish and dominate fire-adapted savanna communities. Because of these characteristics, it is often classified as a high-risk invasive species in warm, frost-free regions across the globe.
Practical Methods for Control and Eradication
Controlling Elephant Grass is challenging because of its extensive root system and ability to regenerate from small fragments, requiring a persistent and integrated approach.
Mechanical Control
For small infestations, mechanical control involves the complete removal of the plant, focusing specifically on digging out all rhizomes and root crowns. Incomplete removal of the underground structures will result in rapid and vigorous regrowth. A more common mechanical strategy is repeated cutting or mowing, which must be done frequently to deplete the plant’s stored root energy reserves over time. For larger areas, heavy machinery may be required to doze out the entire infestation, though this still necessitates careful removal of all plant material from the site.
Cultural Control
Cultural control methods can be employed to manage the spread, such as the use of competitive cover crops or solarization in small, contained areas. Solarization involves covering the area with a heavy, opaque tarp for an extended period. This deprives the plant of light, slowly killing the root system and turning the dead biomass into mulch. This method requires vigilance to manage any new seedlings that emerge once the cover is removed.
Chemical Control
Chemical control is often necessary for established, large infestations, typically involving a foliar application of a broad-spectrum herbicide like glyphosate. Herbicides are most effective when applied to actively growing foliage. Many experts recommend cutting the grass first, allowing it to sprout new growth of 8 to 12 inches, and then spraying the fresh foliage. Due to the robust nature of the root system, multiple applications of the herbicide will be required over several months or even years to achieve complete eradication.