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Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

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Saturday - June 12, 2010

From: Fredericksburg, TX
Region: Southwest
Topic: Invasive Plants, Grasses or Grass-like
Title: Controlling switchgrass in Fredericksburg TX
Answered by: Barbara Medford

QUESTION:

How do you kill switch grass..too much has grown on our property. Originally planted to stop erosion due to oak wilted trees lost on hill behind house, which worked,but now it is everywhere.

ANSWER:

Any plant can get out of hand if it is in good conditions for that plant. Panicum virgatum (switchgrass) is native to your area and well-chosen for the purpose. We understand that too much of a good thing is still roo much, so we will see if we can locate some help in controlling it. Just to help you remember why it is such an effective plant for preventing erosion, see this picture of its roots from Wikipedia Panicum virgatum

This article from Virginia Cooperative Extension Planting and Managing Switchgrass for Forage, Wildlife and Conservation treats Panicum virgatum (switchgrass) as a grass for livestock forage, and laments the fact that overgrazing can sometimes nearly wipe out a stand of the grass before it has a chance to seed. 

In this Floridata article on Panicum virgatum, see this warning:

"Though young plants need protection from weeds, switchgrass becomes a very aggressive competitor as it gets older. Do not plant it in meek company! Early hunters avoided patches of this grass when cutting buffalo meat because the tiny spikes would get embedded in the meat. These sharp spikelets also have an annoying inclination to creep inside one's pants legs."

One of the methods suggested in our research to control this plant was burning. In Central Texas, that is unlikely to be practical, or even allowed, and because of the rhizomatous roots, the plant could still survive and come back. Another suggestion, this one coming to our minds because of the dangers of overgrazing, is to mow the grasses low in the Spring, before they have a chance to spread and set seed. As a last resort, you can try a herbicide for monocots, or grasses. On a large area like this, you would almost have to spray, and in the winds of Central Texas, you could easily kill some things you didn't want to. The Virginia article recommended spraying in late May, so it may already be too hot and/or too late this season to do that. For the time being, we would suggest going the mowing route, especially in areas where you don't want the switchgrass, mowing it down very low and repeatedly, until the roots run out of food. Also, try to avoid doing any irrigation on the areas you don't want, as this grass likes a moist soil.

Here is the product page on switchgrass from Native American seed. 

From our Native Plant Image Gallery:


Panicum virgatum

Panicum virgatum

Panicum virgatum

Panicum virgatum

 

 

 

 

 

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