High seed production is found in plants with high tiller production. Southeastern Europe, now widespread. It is present in many countries of the world. Supposedly introduced to Guam from Samoa. A problem species in Hawaii.
Old plants contain hydrocyanic acid and are dangerous to livestock.
There is some question as to whether or not the species in Western Polynesia is S. halepense or not. The Nature Conservancy's Stewardship Abstract contain information on control methods. Mechanical control of Johnson grass aims to prevent new rhizome production and must be implemented within the first month after shoot emergence. This helps prevent plants from forming rhizomes or seeds. Desiccation of rhizomes can be accelerated by cutting them into fragments less than 5 cm length.