Establishing and Managing Switchgrass

Mark Renz, Extension Weed Scientist

Dan Undersander, Forage Agronomist

Switchgrass (Panicum virgatum) is a vigorous warm season, native perennial.  Switchgrass is adapted to Wisconsin, makes good grazing for livestock and excellent cover for wildlife.  It does best on loams and sandy loams.  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. 

Switchgrass has relatively small seed averaging about 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 broadcast.  Switchgrass should be planted in the spring with no cover crop after soil temperature is above 60^o F.

Weed management can be very difficult while establishing switchgrass.  Several management tools are available, but their effectiveness is based on the weed species present. In general, sites with extensive perennial weed infestations should be avoided as they are difficult to manage while establishing switchgrass.  If possible, reduce the weedy grass populations as much as possible before planting.  This can be done with repeated cultivations and/or burndown herbicide applications before planting switchgrass. 

Annual broadleaf weeds emerging after planting can be controlled with mowing and/or the use of a labeled broadleaf selective herbicide (examples: Banvel, Clarity, Escort, 2,4-D, Weedmaster).  If mowing new seedings, leave at least 6 inches of stubble.  If a broadleaf herbicide is used, wait until switchgrass plants have at least 3-4 leaves (or are 3-4 inches tall) before application to avoid injury. 

Weedy grasses are much more difficult to control as few tools can control grass weeds without injuring switchgrass seedlings.  Some herbicides have activity on weedy grasses while providing minimal injury to switchgrass seedlings (Pursuit, Certainty, Drive). While these herbicides are registered for use in Wisconsin, they have not been evaluated for efficacy and safety in switchgrass establishment under Wisconsin’s growing conditions, so caution should be used.  Please note that atrazine is not registered for use in switchgrass in Wisconsin.

Plant 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.  Warm season grasses are slow to establish.  Development of a root system is important so warm season grasses should not be grazed or cut during the seeding year unless growth is exceptional.

Sunburst is an improved variety of switchgrass developed by the South Dakota Agricultural Experiment Station.  It reaches anthesis about two weeks earlier than Blackwell and has similar yields.  It has better seedling vigor than most other varieties.  Other varieties exist that grow well in Wisconsin.

Grazing can begin when switchgrass is 10 to 12 inches tall.  This grass decreases with heavy use but can be managed successfully similar to other warm season pasture grasses.  Its rapid early growth is especially palatable to livestock.  It also makes good hay if cut when seed heads begin to form.  Switchgrass becomes rapidly unpalatable and low in quality as it approaches heading.

Pastures should be stocked with enough cattle to graze the switchgrass down to 4 inches within two weeks.  Then cattle should be removed and the pasture allowed a month to recover.  Graze regrowth to no shorter than 8 inches of stubble and leave for winter.  The final grazing should be on or before Sept. 1.

If haying, cut at the boot stage leaving a 3- to 4-inch stubble.  Then graze until late August leaving an 8-inch stubble.

Information summarized by Mark Renz and Dan Undersander, 3/15/07