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Switch grass, or old switch panic grass, (Panicum virgatum) is a bunchgrass native to North America. It occurs from Mexico to southern Canada. This grass grows up to 2.7 m (8 feet) tall in thick stands. Switch grass is perennial, meaning it lives for more than one year, and self-seeding, meaning it can propagate itself by seed. These characters allow a stand to exist a long time - up to 10 years - even if the blades are eaten or harvested.
Switch grass grows with several other native grass species. These include big bluestem, indiangrass, little bluestem, sideoats grama, and eastern gamagrass. Historically, these grasses covered millions of acres of North American climax tallgrass prairie land east of the Rocky Mountains. Now, introduced crops such as wheat, oats, corn and non-native grasses occupy much of this range.
Because it is happiest in mesic (moist) soils, switch grass is usually found in wetter, lowland habitats, but it is highly adaptable to many soil types and conditions. It can withstand flooding. It has a deep root system helpful for tapping needed water sources. The expansive roots stabilize soils and prevent soil erosion caused by flooding or runoff. Also, the roots increase the permeability and fertility of the soil. For these reasons, projects to restore roadsides, old mine sites, dams and other damaged areas commonly include switch grass in plantings.
A "warm-season" grass, switch grass is dormant until late in the spring, when its growth season starts. Stands of switch grass spread outwards from short underground runners, called rhizomes. In the upper limits of its range it is productive through early fall. In the warm, humid gulf coast area its growing season can last eight months.
Switch grass stands attract an abundance of wildlife. The plant's tall cover and plentiful small seeds are important resources for songbirds and game birds (pheasants, quail, grouse, prairie chicken). When it occurs in marshes or on the edges of water bodies, switch grass provides excellent nesting sites for ducks and other waterfowl.
Farmers grow fields of switch grass for grazing and to harvest for high-quality hay. Before the seeds mature, the leaf blades are nutritious and palatable, especially for cattle. Afterwards, the grass gets tough and nutrient levels decline. Wild ungulates rarely eat switch grass although deer occasionally dig up and eat the rhizomes when other food sources are scarce. Grasshoppers and leafhoppers can be a pest, killing the plants by foraging on the young shoots.
Switch grass is processed into burnable pellets that can be used for household heat. These can also be used to fuel industrial boilers. Since the early 2000s, switch grass has been targeted as a possible renewable bio-fuel. It is cheaper to grow and more efficient than corn for this purpose. Scientists recently bio-engineered a bacteria species that can convert switch grass to ethanol. This is promising for the development of this technology.
(Jimmy Carter Plant Materials Center. 2011; Chung et al. 2014; Jimmy Carter plant Materials Center 2011; McLaughlin et al. 2005; Schmer et al. 2008; Uchytl 1993; Wikipedia 2015)