Johnson Grass

Sorghum halepense

 

Johnson grass is a very aggressive, perennial grass. It occurs in dense clumps that spread by seed and rhizomes to form nearly pure stands. The thick rhizomes live over winter and in the spring send out new, white, spur-like shoots. In clay soils 80% of the rhizomes are in the top four inches of soil. In sandy loam soil, 80% occur in the top six inches. However, rhizomes may grow downward through cracks to a depth of 10 to 20 inches. The grass leaves emerge late in spring and the plant forms seed by July 1. A single plant may produce over 80,000 seeds per year. Stems and leaves die back after the first frost, but the dead litter often covers the ground all winter. Rhizome cuttings commonly form new plants, making it very difficult to eradicate. In the home landscape, digging up and bagging the grass clumps can be an option but any broken off tillers (roots) can form new plants.

The most effective way of eliminating it is to dig it up. If you have a small population, this is a possibility. To make it easier to remove, you should thoroughly soak the ground with water around the base of the plants. You must get all of the roots out of the ground or you will have new plants sprouting from them. You will have to be watchful and persistent about removing new shoots along with their roots when they appear.