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Panicum virgatum, commonly known as switchgrass, is a warm season native to North America, where it occurs naturally from 55°N latitude in Canada southwards into the United States and Mexico. Switchgrass is one of the dominant of the central North American tallgrass prairie and can be found in remnant prairies, in native grass , and naturalized along roadsides. It is used primarily for soil conservation, production, game cover, as an , in projects, fiber, electricity, heat production, for of atmospheric , and more recently as a crop for the production of and .

Other common names for switchgrass include tall panic grass, Wobsqua grass, blackbent, tall prairiegrass, wild , thatchgrass, and Virginia switchgrass.


Description
Switchgrass is a hardy, deep-rooted, grass that begins growth in late spring. It can grow up to high, but is typically shorter than grass or . The are long, with a prominent midrib. Switchgrass uses C4 carbon fixation, giving it an advantage in conditions of and high temperature. Its have a well-developed , often up to long, and it bears a good crop of . The seeds are long and up to wide, and are developed from a single-flowered . Both are present and well developed. When ripe, the seeds sometimes take on a pink or dull-purple tinge, and turn golden brown with the foliage of the plant in the fall. Switchgrass is both a perennial and self-seeding crop, which means farmers do not have to plant and reseed after annual harvesting. Once established, a switchgrass stand can survive for ten years or longer. Unlike , switchgrass can grow on marginal lands and requires relatively modest levels of chemical fertilizers. Overall, it is considered a resource-efficient, low-input crop for producing bioenergy from farmland. Switchgrass roots.jpg|upright=2.27|Root system of switchgrass grown at the Panicum virgatum fruit.jpg|Seeds, Kirt Prairie


Habitat
Much of North America, especially the prairies of the Midwestern United States, was once prime habitat to vast swaths of native grasses, including switchgrass, ( Sorghastrum nutans), eastern gamagrass ( Tripsacum dactyloides), ( Andropogon gerardi), ( Schizachyrium scoparium) and others. As European settlers began spreading west across the continent, the native grasses were plowed under and the land converted to crops such as , , and . Introduced grasses such as , , and also replaced the native grasses for use as hay and pasture for cattle.


Distribution
Switchgrass is a versatile and adaptable plant. It can grow and even thrive in many weather conditions, lengths of growing seasons, soil types, and land conditions. Its distribution spans south of latitude 55°N from to , south over most of the east of the , and further south into . As a warm-season grass, most of its growth occurs from late spring through early fall; it becomes dormant and unproductive during colder months. Thus, the productive season in its northern habitat can be as short as three months, but in the southern reaches of its habitat the growing season may be as long as eight months, around the area.
(2025). 9780962959837, International Plant Nutrition Institute. .

Switchgrass is a diverse species, with striking differences between plants. This diversity, which presumably reflects evolution and adaptation to new environments as the species spread across the continent, provides a range of valuable traits for breeding programs. Switchgrass has two distinct forms, or "cytotypes": the lowland , which tend to produce more biomass, and the upland cultivars, which are generally of more northern origin, more cold-tolerant, and therefore usually preferred in northern areas. Upland switchgrass types are generally shorter, at ≤ tall, and less coarse than lowland types. Lowland cultivars may grow to ≥ in favorable environments. Both upland and lowland cultivars are deeply rooted, > in favorable soils, and have short . The upland types tend to have more vigorous rhizomes, so the lowland cultivars may appear to have a habit, while the upland types tend to be more sod-forming. Lowland cultivars appear more plastic in their morphology, produce larger plants if stands become thin or when planted in wide rows, and they seem to be more sensitive to moisture stress than upland cultivars.Establishing and Managing Switchgrass as an Energy Crop, Forage and Grazinglands, 2008.

In native prairies, switchgrass is historically found in association with several other important native tallgrass prairie plants, such as big bluestem, indiangrass, little bluestem, , eastern gamagrass, and various (, , , and prairie coneflower). These widely adapted tallgrass species once occupied millions of hectares.Switchgrass as a Bioenergy Crop, ATTRA - National Sustainable Agricultural Information Service, 2006.

Switchgrass’ suitability for cultivation in the is being studied by Argentina's Instituto Nacional de Tecnología Agropecuaria (INTA).


Establishment and management
Switchgrass can be grown on land considered unsuitable for production, including land that is too for production, as well as and soils in regions that typically produce low of other crops. No single method of establishing switchgrass can be suggested for all situations. The crop can be established both by and conventional . When seeded as part of a diverse mixture, planting guidelines for warm-season grass mixtures for conservation plantings should be followed. Regional guidelines for growing and managing switchgrass for bioenergy or conservation plantings are available. Several key factors can increase the likelihood of success for establishing switchgrass. These include:http://reap-canada.com/online_library/feedstock_biomass/5-Establishing%20and%20Managing%20Switchgrass%20as%20an%20Energy%20Crop%20_Parrish%20et%20al.,%202008.pdf David J. Parrish, John H. Fike, David I. Bransby, Roger Samson. Establishing and Managing Switchgrass as an Energy Crop. Forage and Grazinglands. 2008
  • Planting switchgrass after the soil is well warmed during the spring.
  • Using seeds that are highly and planting 0.6 - 1.2 cm deep, or up to 2 cm deep in sandy soils.
  • Packing or firming the soil both before and after seeding.
  • Providing no at planting to minimize competition.
  • Controlling with chemical and/or cultural control methods.
and properly labeled are recommended for . Chemical weed control can be used in the fall prior to establishment, or before or after planting. Weeds should be mowed just above the height of the growing switchgrass. herbicides, such as 2,4-D, should be avoided as they are known to reduce development of switchgrass when applied early in the establishing year. Plantings that appear to have failed due to weed infestations are often wrongly assessed, as the failure is often more apparent than real. Switchgrass stands that are initially weedy commonly become well established with appropriate management in subsequent years. Once established, switchgrass can take up to three years to reach its full production potential. Depending on the region, it can typically produce 1/4 to 1/3 of its yield potential in its first year and 2/3 of its potential in the year after seeding.

After establishment, switchgrass management will depend on the goal of the seeding. Historically, most switchgrass seedings have been managed for the Conservation Reserve Program in the US. Disturbance such as periodic mowing, burning, or disking is required to optimize the stand's utility for encouraging . Increased attention is being placed on switchgrass management as an . Generally, the crop requires modest application of nitrogen fertilizer, as it is not a heavy feeder. Typical nitrogen (N) content of material in the fall is 0.5% N. Fertilizer nitrogen applications of about 5 kg N/ applied for each of removed is a general guideline. More specific recommendations for fertilization are available regionally in . Herbicides are not often used on switchgrass after the seeding year, as the crop is generally quite competitive with weeds. Most bioenergy conversion processes for switchgrass, including those for cellulosic ethanol and pellet fuel production, can generally accept some alternative in the . Stands of switchgrass should be harvested no more than twice per year, and one cutting often provides as much biomass as two. Switchgrass can be harvested with the same used for production, and it is well-suited to or bulk field harvesting. If its is properly taken into consideration, switchgrass can offer great potential as an energy crop.http://www.reap-canada.com/online_library/feedstock_biomass/Optimization%20of%20switchgrass%20management%20for%20commercial%20fuel%20pellet%20production%20(Samson%20et%20al.,%202007).pdf Samson, R., Bailey-Stamler, S., & Ho Lem, C. Optimization of Switchgrass Management for Commercial Fuel Pellet Production (Final report prepared by REAP-Canada for the Ontario Ministry of Food, Agriculture and Rural Affairs (OMAFRA) under the Alternative Renewable Fuels Fund). 2008


Uses
Switchgrass can be used as a for energy production, as for soil conservation, and to control , for and , as game cover, and as feedstock for biodegradable plastics. It can be used by cattle farmers for and and as a substitute for wheat in many applications, including bedding, straw bale housing, and as a substrate for growing mushrooms. Additionally, switchgrass is grown as a drought-resistant in average to wet soils and in full sun to part shade.


Moth host plant
It is the preferred larval host plant of Dargida rubripennis. It is also a larval host for the and the .The Xerces Society (2016), Gardening for Butterflies: How You Can Attract and Protect Beautiful, Beneficial Insects, Timber Press.


Bioenergy
Switchgrass has been studied as a potential renewable crop since the mid-1980s, because it is a native warm season grass with the ability to produce moderate to high on marginal farmlands. It is now being considered for use in several bioenergy conversion processes, including cellulosic ethanol production, , and direct combustion for applications. The main advantages of switchgrass as a bioenergy crop are its stand longevity, drought and flooding tolerance, relatively low and input requirements, ease of management, hardiness in poor soil and climate conditions, and widespread adaptability in climates. In some warm humid southern zones, such as , it has the ability to produce up to 25 oven-dry tonnes per hectare (ODT/ha). A summary of switchgrass yields across 13 research trial sites in the found the top two cultivars in each trial to yield 9.4 to 22.9 t/ha, with an average yield of 14.6 ODT/ha. However, these yields were recorded on small plot trials, and commercial field sites could be expected to yield at least 20% less. In the United States, switchgrass yields appear to be highest in warm humid regions with long growing seasons such as the US Southeast and lowest in the dry short season areas of the Northern . The energy inputs required to grow switchgrass are favorable when compared with such as , , or , which can require relatively high energy inputs for field operations, crop drying, and fertilization. Whole plant perennial C4 grass feedstocks are desirable biomass energy feedstocks, as they require fewer fossil energy inputs to grow and effectively capture solar energy because of their C4 system and perennial nature. One study concluded that it takes from 0.97 to 1.34 GJ to produce 1 tonne of switchgrass, compared with 1.99 to 2.66 GJ to produce 1 tonne of corn. Another study found that switchgrass uses 0.8 GJ/ODT of compared to grain corn's 2.9 GJ/ODT. As switchgrass contains approximately 18.8 GJ/ODT of biomass, the energy output-to-input ratio for the crop can be up to 20:1.
(2025). 9781402086533, Springer.
This highly favorable ratio is attributable to its relatively high energy output per hectare and low energy inputs for production.

Considerable effort is being expended to develop switchgrass as a cellulosic ethanol crop in the USA. In George W. Bush's 2006 State of the Union Address, he proposed using switchgrass for ethanol; since then, over US$100 million has been invested into researching switchgrass as a potential biofuel source."Since that mention in the 2006, investment in switch grass has exploded, thanks in large part, experts say, to the President's speech. Venture capitalists have poured over $100 million into private companies that are exploring the technology necessary to convert switchgrass into fuel, and large publicly owned companies are also directing their research dollars into biofuels." Switchgrass has the potential to produce up to 380 liters of per tonne harvested; however, current technology for herbaceous biomass conversion to ethanol is about 340 liters per tonne. Iogen Corporation Iogen Corporation, 2009. By contrast, corn ethanol yields about 400 liters per tonne.Farrell, A.E. Ethanol Can Contribute to Energy and Environmental Goals. Science. Volume 311. 2006. 506-508.

The main advantage of switchgrass over corn as an ethanol feedstock is that switchgrass's cost of production is generally about 1/2 that of grain corn, and more biomass energy per hectare can be captured in the field. hus, switchgrass cellulosic ethanol should give a higher of ethanol per hectare at lower cost. However, this will depend on whether the cost of constructing and operating cellulosic ethanol plants can be reduced considerably. The switchgrass ethanol industry energy balance is also considered to be substantially better than that of . During the process, the fraction of switchgrass can be burned to provide sufficient and to operate the . Studies have found that for every unit of energy input needed to create a biofuel from switchgrass, four units of energy are yielded. In contrast, corn ethanol yields about 1.28 units of energy per unit of energy input.Wang, M., Wu, M., & Huo, H. Life-cycle energy and greenhouse gas emission impacts of different corn ethanol plant types. Environmental Research Letters. Volume 2. 2007. 1-13. A 2008 study from the Great Plains indicated that for ethanol production from switchgrass, this figure is 6.4, or alternatively, that 540% more energy was contained in the ethanol produced than was used in growing the switchgrass and converting it to . However, there remain commercialization barriers to the development of cellulosic ethanol technology. Projections in the early 1990s for commercialization of cellulosic ethanol by the year 2000 have not been met. The commercialization of cellulosic ethanol is thus proving to be a significant challenge, despite considerable research efforts.

Thermal energy applications for switchgrass appear to be closer to near-term scale-up than cellulosic ethanol for industrial or small-scale applications. For example, switchgrass can be that are subsequently burned in used to heat homes (which typically burn corn or ). Switchgrass has been widely tested as a substitute for in . The most widely studied project to date has been the Chariton Valley Project in . The Show-Me-Energy Cooperative (SMEC) in Show Me Energy Cooperative is using switchgrass and other warm-season grasses, along with residues, as feedstocks for pellets used for the firing of a coal-fired power plant. In , switchgrass is being used on a pilot scale as a feedstock for commercial heating applications. studies have been undertaken and it appears to be well-suited as a commercial boiler fuel. Research is also being undertaken to develop switchgrass as a pellet fuel because of lack of surplus wood residues in eastern Canada,Bailey Stamler, S., R. Samson and C. Ho Lem. Biomass resources options: Creating a BIOHEAT supply for the Canadian greenhouse industry. Final report to Natural Resources Canada, Ottawa. 2006. 38 pages as a slowdown in the forest products industry in 2009 is now resulting in shortages throughout Eastern North America. Generally speaking, the direct firing of switchgrass for thermal applications can provide the highest net energy gain and energy output-to-input ratio of all switchgrass bioconversion processes. Research has found switchgrass, when pelletized and used as a solid biofuel, is a good candidate for displacing fossil fuels. Switchgrass pellets were identified to have a 14.6:1 energy output-to-input ratio, which is substantially better than that for liquid biofuel options from farmland. As a greenhouse gas mitigation strategy, switchgrass pellets were found to be an effective means to use farmland to mitigate greenhouse gases on the order of 7.6–13 tonnes of CO2 per hectare. In contrast, switchgrass cellulosic ethanol and corn ethanol were found to mitigate 5.2 and 1.5 tonnes of CO2 per hectare, respectively.

Historically, the major constraint to the development of grasses for thermal energy applications has been the difficulty associated with burning grasses in conventional , as biomass quality problems can be of particular concern in combustion applications. These technical problems now appear to have been largely resolved through crop management practices such as fall and spring that allow for leaching to occur, which leads to fewer -forming compounds (such as K and Cl) and N in the grass. This reduces clinker formation and , and enables switchgrass to be a clean combustion fuel source for use in smaller combustion appliances. Fall harvested grasses likely have more application for larger commercial and industrial boilers."Samson et al. 2007": http://www.reap-canada.com/online_library/feedstock_biomass/The%20Emerging%20Agro-Pellet%20Industry%20in%20Canada%20(Samson%20et%20al.,%202007).pdf R. Samson, S. Bailey and C. Ho Lem. The Emerging Agro-Pellet Industry in Canada. 2007"Samson et al., 2008": In regions where the and contents of switchgrass cannot be successfully leached out for thermal applications, it may be that applications for switchgrass will prove more promising. Switchgrass has demonstrated some promise in biogas research as an alternative feedstock to whole plant corn for biogas digesters."Frigon et al. 2008 http://www.gtmconference.ca/site/downloads/2008presentations/5B3%20-Frigon.pdf J.C. Frigon, P. Mehta, S.R. Guiot. The bioenergy potential from the anaerobic digestion of switchgrass and other energy crops. National Research Council Canada. Growing the Margins Conference: Energy, Bioproducts and Byproducts from farms and food sectors. April 2–5, 2008, London, Ontario Switchgrass is also used to heat small industrial and farm buildings in and through a process used to make a low quality substitute."plentiful_switchgrass"

Bai et al. (2010) conducted a study to analyze the environmental sustainability of using switchgrass plant material as a feedstock for production. Life cycle analysis was used to make this assessment. They compared efficiency of E10, E85, and ethanol with . They took into account air and water emissions associated with growing, managing, processing and storing the switchgrass crop. They also factored in the transportation of the stored switchgrass to the ethanol plant where they assumed the distance was 20 km. The reductions in global warming potential by using E10 and E85 were 5 and 65%, respectively. Their models also suggested that the “human toxicity potential” and “eco-toxicity potential” were substantially greater for the high ethanol fuels (i.e., E85 and ethanol) than for gasoline and E10.

In 2014, a genetically altered form of the bacterium Caldicellulosiruptor bescii was created which can cheaply and efficiently turn switchgrass into ethanol.


Biodegradable plastics production
In a novel application, US scientists have genetically modified switchgrass to enable it to produce polyhydroxybutyrate, which accumulates in beadlike granules within the plant's cells. Biomass Combo, Chemical & Engineering News, 86, 33, 18 Aug. 2008, p. 13 In preliminary tests, the dry weight of a plants leaves were shown to comprise up to 3.7% of the polymer. Plant Biotechnology Journal, 2008, 6, 663 Such low accumulation rates do not, as of 2009, allow for commercial use of switchgrass as a biosource.


Soil conservation
Switchgrass is useful for soil conservation and , particularly in the United States and Canada, where switchgrass is endemic. Switchgrass has a deep fibrous root system – nearly as deep as the plant is tall. Since it, along with other native grasses and , once covered the plains of the United States that are now the , the effects of the past switchgrass habitat have been beneficial, lending to the fertile farmland that exists today. The deep fibrous root systems of switchgrass left a deep rich layer of in the soils of the Midwest, making those soils some of the most productive in the world. By returning switchgrass and other perennial prairie grasses as an agricultural crop, many marginal soils may benefit from increased levels of organic material, permeability, and fertility, due to the grass's deep root system.

Soil , both from wind and water, is of great concern in regions where switchgrass grows. Due to its height, switchgrass can form an effective wind erosion barrier. Its root system, also, is excellent for holding soil in place, which helps prevent erosion from flooding and runoff. Some highway departments (for example, KDOT) have used switchgrass in their seed mixes when re-establishing growth along roadways. It can also be used on sites, dikes, and pond dams. Conservation districts in many parts of the United States use it to control erosion in grass waterways because of its ability to anchor soils while providing habitat for wildlife.


Forages and grazing
Switchgrass is an excellent for cattle; however, it has shown toxicity in horses, sheep, and goats
(2025). 9781845932732, CABI Pub.. .
through chemical compounds known as , which cause and liver damage in these animals. Researchers are continuing to learn more about the specific conditions under which switchgrass causes harm to these species, but until more is discovered, it is recommended that switchgrass not be fed to them. For cattle, however, it can be fed as hay, or grazed.

Grazing switchgrass calls for watchful management practices to ensure survival of the stand. It is recommended that grazing begin when the plants are about 50 cm tall, that grazing be discontinued when the plants have been eaten down to about 25 cm, and that the pasture be rested for 30–45 days between grazing periods. Switchgrass becomes stemmy and unpalatable as it matures, but during the target grazing period, it is a favorable forage with a relative feed value (RFV) of 90–104. The grass's upright growth pattern places its growing point off the soil surface onto its stem, so leaving 25 cm of stubble is important for regrowth. When harvesting switchgrass for hay, the first cutting occurs at the late boot stage – around mid-June. This should allow for a second cutting in mid-August, leaving enough regrowth to survive the winter.


Game cover
Switchgrass is well known among wildlife conservationists as good forage and habitat for upland species, such as , , , and , and , with its plentiful small seeds and tall cover. A study published in 2015 has shown that switchgrass, when grown in a traditional monoculture, has an adverse impact on some wildlife. Depending on how thickly switchgrass is planted, and what it is partnered with, it also offers excellent forage and cover for other wildlife across the country. For those producers who have switchgrass stands on their farm, it is considered an environmental and aesthetic benefit due to the abundance of wildlife attracted by the switchgrass stands. Some members of Prairie Lands Bio-Products, Inc. in Iowa have even turned this benefit into a profitable business by leasing their switchgrass land for hunting during the proper seasons. The benefits to wildlife can be extended even in large-scale agriculture through the process of strip harvesting, as recommended by The Wildlife Society, which suggests that rather than harvesting an entire field at once, strip harvesting could be practiced so that the entire habitat is not removed, thereby protecting the wildlife inhabiting the switchgrass.


Ornamental cultivars
Panicum virgatum are used as ornamental plants in gardens and landscaping. The following have gained the Royal Horticultural Society's Award of Garden Merit:-
  • 'Dallas Blues'
  • "Heavy Metal'
  • 'Hänse Harms'
  • 'Northwind'
  • 'Shenandoah'


Forage and Bioenergy Cultivars
Panicum virgatum has also been extensively cultivated for forage and bioenergy purposes. Unlike ornamental types, these cultivars are bred for traits such as high biomass production, rapid growth, deep rooting, and resilience to environmental stresses. Forage types are commonly used in grazing systems due to their high digestibility and adaptability across diverse soil conditions. Bioenergy-specific cultivars are developed to maximize lignocellulosic biomass for renewable fuel production and are particularly valuable in sustainable energy systems. In addition to environmental benefits, these cultivars contribute to increased farm profitability, especially when grown on marginal lands that are less suitable for conventional food crops.
+Forage/Conservation varieties !Cultivar !Release Year !Ecotype !USDA Zones !Plant Introduction Number
Blackwell1944Upland5-7 PI421520
Caddo1955Upland6-7 PI 476297
Sunburst1998Upland3-5 PI 598136
+Bioenergy varieties !Cultivar !Release

Year !Ecotype !USDA

Zones !Plant Introduction number

BoMaster2008Lowland6-8PI 645256
(2025). 9781447129028, Springer London. .
Liberty2014Lowland4-6PI 669371
Independence2021Lowland5b-7b PI 704577


See also


External links

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