King Ranch Bluestem

Green Side Up

Any trip around rural Stephens County or surrounding areas will expose the traveler to great waves of 18 to 48 inch tall grass bearing loose terminal seed heads on stems that are naked below the red to purplish tinged seed heads. This non-native grass also appears in vacant lots in urban areas and in areas on your property that do not receive as much attention as you would like. This prolific pest is King Ranch Bluestem.

King Ranch Bluestem (KR Bluestem) was introduced into this country in the late 1890s or early 1900s. It was not noticed on the King Ranch until about 1937 and being associated with that organization by name. Since then it has become established throughout much of the southern and central parts of the state and has extended up into Oklahoma.

KR Bluestem is a bunchgrass that grows in tufts with upright or spreading stems. It is a perennial that blooms in early spring and the seed heads mature in the fall. It was originally introduced to be a forage grass for livestock. It grows well and establishes easily, is very tough, and is drought tolerant. When KR Bluestem is used as a permanent pasture it can produce fair grazing for cattle and sheep and can be grazed throughout the winter. It also produces good hay. KR Bluestem has been planted by the Texas Department of Transportation along roadways as an erosion control. A Master Naturalist friend derisively refers to it as TxDOT Bluestem.

Unfortunately, like many bothersome plants that have been introduced, it tends to not stay where it is planted leading to its being classified as invasive. It has adapted to well-drained shallow sandy, loam and clay soils. It does not appear to do well in acidic soils. KR Bluestem is known to have displaced native grasses in large areas of central and south Texas. It has been accused of being the cause of reduced displays of spring wild flowers. It has also been shown to contribute to a decline in bird and insect diversity.

Controlling KR Bluestem is not an easy task. To my knowledge there is no herbicide specifically labeled for KR Bluestem. Glyphosate herbicides will kill it, but I do not recommend them. Glyphosate herbicides are non-specific and will kill surrounding plants as well. These herbicides have gotten a lot of negative press lately and should be approached with extreme caution. If KR Bluestem appears in a lawn the best solution is to dig it out. Intensive mowing during the growing season, but before seed production and burning are options that can be used instead of herbicides.

Speaking of invasive grasses what about Johnson grass? It has been reported that Texas taxpayers spent over $50 million 20 years ago for chemical control of Johnson grass along Texas roadsides alone. I shudder to think what the current figure is. No wonder it has earned the reputation of being one of the ten worst weeds in the world.

Johnson grass is well adapted to compete with crop plants and to spread widely. It not only reproduces by seeds but it also by thick rhizomes. A single plant may produce more than 80,000 seeds and 275 feet of rhizomes in a single growing season. The seeds can remain viable in the soil for up to ten years and the rhizomes can be found several feet deep in the soil.

Controlling Johnson grass in the home environment involves intensive close mowing for a couple of years to weaken the plant and concentrate the rhizomes near the surface.

Once thought to be good forage for livestock, Johnson grass has properties that can cause cyanide poisoning in horses and cattle if it is eaten in quantity.