Cogongrass

Prepared by Joey Williamson, Ph.D., HGIC Horticulture Extension Agent, Clemson University. (New 11/08. Images added 3/09.)

HGIC 2318

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Cogongrass (Imperata cylindrica) is one of the world’s ten worst weeds and has already invaded 153 billion acres worldwide. Cogongrass is becoming established in Florida, Georgia, Alabama, Mississippi and Louisiana, and has now been found in South Carolina. In Florida alone, it has infested one million acres, where it has displaced many native species of plants. Cogongrass will invade pastures, where it reduces the forage quality because its leaves are unpalatable to livestock. It can quickly displace other vegetation in forests and fields, including native plants that birds and small animals need for shelter and forage.

Cogongrass in bloom
Cogongrass in bloom
Fred Singleton, Department of Plant Industry, Clemson University

The Means of Spread

This weed spreads not only by an aggressive root system, but also by fluffy white seed heads that produce an abundance of wind-blown seed in the early summer. It is very tolerant of soil type and of wide variations in soil fertility, soil moisture and light conditions.

Cogongrass seedhead
Cogongrass seedhead
Steve Compton, Department of Plant Industry, Clemson University

Identification

Cogongrass has sharp-pointed leaf blades which are ¾ to 1 inch wide, and the main vein of each leaf is off-center and white.

Off-center, white, main vein in cogongrass
Off-center, white, main vein in cogongrass leaf
Mark Atwater, Weed Control Unlimited, Inc., US

For more information on cogongrass identification, please see: www.cogongrass.org/cogongrassid.pdf

Japanese Bloodgrass

Japanese bloodgrass (Imperata cylindrica ‘Red Baron’) is a 2-foot tall perennial grass with red and lime-green leaves. The problem is that Japanese bloodgrass (‘Red Baron’ bloodgrass) is a variety of cogongrass, and this red-leafed ornamental grass can revert back to the extremely aggressive, 4 to 5 foot-tall, green form. Sales of this popular ornamental grass have been halted in South Carolina, but plants have been brought in from other states. Although this grass might make a nice colorful addition to the perennial garden, it’s highly aggressive nature warrants us to think twice about planting it.

Japanese bloodgrass
Japanese bloodgrass
Karen Russ, ©2009 HGIC, Clemson Extension

Non-invasive Alternatives

For gardeners who would like to have a red-leafed ornamental grass in their perennial beds, there are other choices. There are three cultivars of our native switchgrass (Panicum virgatum) that have red foliage, which is especially prominent in the fall.

‘Shenandoah’, ‘Squaw’ and ‘Rotstrahlbusch’ are non-invasive red switchgrasses for sunny gardens, and all three will adapt to a wide range of soil conditions. ‘Shenandoah’ looks the most like Japanese bloodgrass, as its foliage starts out green with the tips turning red in early summer.

Panicum virgatum 'Shenandoah'
Panicum virgatum ‘Shenandoah’
Karen Russ, ©2009 HGIC, Clemson Extension

Report Any Sightings

Clemson University’s Department of Plant Industry is a member of a task force, which includes the SC Forestry Commission and the US Forest Service, with the goal of preventing the spread of cogongrass within South Carolina. If you have Japanese bloodgrass or have seen cogongrass in your area, contact the Clemson Department of Plant Industry at 864-646-2140. Any sighting will be investigated.

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