Switchgrass (Panicum virgatum) is a vigorous, warm-season perennial grass planted for many purposes including livestock grazing, wildlife cover and as a biofuel crop.
Switchgrass begins growth in late spring and continues through the summer if moisture is available. It grows 3 to 6 feet in small to large sodded clumps that spread slowly from numerous scaly, creeping rhizomes. The leaves have a bluish cast and can attain a length of 2 feet.
At the junction of the leaf blade and leaf sheath, the ligule is a dense ring or cup of hairs on the upper leaf surface.
The panicles are pyramid-shaped with many purplish spikelets. Under native conditions it is usually found along creeks, streams and protected areas, but establishment and productivity has been best in fields with loam to sandy loam soils.
Varieties and ecotypes
Switchgrass varieties and ecotypes vary widely in their adaptation to environmental conditions. Cold winters, hot summers and day length are the most important of these environmental factors, all of which vary according to latitude.
Because of this, switchgrass varieties or ecotypes should be moved no more than one hardiness zone from their origin.
Establishment
Switchgrass has relatively small seed, averaging approximately 370,000 seeds per pound. The suggested seeding rate is 6 to 7 pounds of pure live seed when close-drilled (8 inches or less between rows) or broadcasted.
Switchgrass should be planted in the spring after soil temperature is above 60ºF. Planting is recommended on a firm, well-prepared seedbed at a depth of 1/2- to 3/4-inch.
Cultipacking after planting helps establish good contact with soil and speeds germination.
No-till planting of switchgrass has also been successful. If possible, plant after no-till soybeans, as no-till corn fields have rougher terrain that can make harvesting of biomass difficult.
Switchgrass is slow to establish and many of the resources collected in the establishment years are used to develop an extensive root system.
Due to this, switchgrass should not be grazed or cut during the seeding year unless weed density is high or growth is exceptional.
Weed management
Several management methods can be utilized for managing weeds while establishing switchgrass. Selection of the most appropriate method is based on the weed species present and the appropriate density.
In general, sites with extensive perennial grass infestations (e.g. quackgrass) should be avoided as they are difficult to manage while establishing switchgrass.
If possible, reduce weed populations as much as possible before planting. This can be done with repeated cultivations or burndown herbicide applications before planting switchgrass.
Growing Roundup Ready corn or soybeans years prior to establishment of switchgrass is also effective in reducing weed populations, especially perennial weeds.
Annual broadleaf weeds are common in the establishment year and if populations are dense, establishment can be reduced.
These weeds can be controlled with timely mowing or the use of a labeled broadleaf herbicide. If mowing, leave at least 6 inches of stubble.
If a broadleaf herbicide is used, wait until switchgrass plants have at least 3 to 4 leaves (or are 3 to 4 inches tall) before application to avoid injury.
Weedy grasses can also be troublesome, as they are much more difficult to control without injuring switchgrass seedlings.
Switchgrass uses
• Biofuel
Switchgrass is being promoted for several uses as a biofuel. Uses include burning for electricity, production of cellulosic ethanol and heating of homes and businesses.
For biofuel production, fields are recommended to be harvested once per year in the late summer to winter.
Harvesting two to three weeks after the first frost will allow the plant to recycle nutrients and likely reduce future fertilization as well as drying costs.
• Grazing
Switchgrass is an excellent food source for livestock and is especially palatable before plants flower, but its quality and palatability decline rapidly as it approaches heading.
Fields can begin being grazed when plants are 10 to 12 inches tall, and should be grazed down to 4 inches within two weeks. Then livestock should be removed and the pasture allowed to recover.
Graze regrowth to no shorter than 8 inches. If haying, cut at the boot stage leaving 3 to 4 inches of stubble.
While switchgrass is a good forage for livestock, its persistence decreases with overgrazing, similar to other warm-season pasture grasses; therefore fields must be managed carefully.
• Wildlife/conservation
Switchgrass provides excellent habitat for wildlife when used exclusively or in combination with other plant species.
The vertical growth habit of switchgrass provides beneficial cover for many upland birds, which allows for quality nesting sites and protection from predators.
Switchgrass is used extensively as grass filter strips for erosion control, flood management and reduction of nutrient loading of waterways. And growing switchgrass can also help restore the original tallgrass prairie, one of our more endangered ecosystems. FG
—Excerpts from University of Wisconsin Extension website
