Sorghum halepense is known more colloquially as Johnsongrass and is considered one of the ten most invasive weeds in the world. Johnsongrass is prevalent on every continent except Antarctica. While it was originally native to the Mediterranean and the Middle East, it was introduced to the United States by Colonel William Johnson in 1840, and since then it has been challenging to manage and contain.
Johnsongrass is a perennial weedy grass that grows upwards of 6 feet tall. Leaves are around 2 feet long and alternately arranged around a course stem, and presents with purple flowers on loose 6-inch long panicles containing the seeds. Seeds are typically arranged in sets of 3, each containing single awns. Flowers bloom from May through October. Johnsongrass grows in clumpy areas, with roots matting together in large colonies.
It grows in just about every region of the world. The ability for Johnsongrass to reproduce both through the root system and by seeds makes it easy to spread and difficult to eradicate. It is found almost anywhere there is disturbed soil or earth. It is commonly found in newly seeded turf as well as in roadsides, agricultural fields, ditches, open grasslands, pastures, or anywhere there is soil for the roots to grab onto.
Why Johnsongrass is a Problem
Initially, Johnsongrass was used for preventing soil erosion due to the matting roots as well as for pasture for livestock to graze. The weed is so incredibly pervasive, however, and it quickly overruns areas and competes for nutrients, water, and sun. The weed also can become cyanotic in certain conditions, which can be fatal to livestock when eaten in large quantities.
Johnsongrass is extremely difficult to eradicate because of the ability for plants to regenerate from the roots as well as through seeds. For home lawns and turf, regular applications of weed control along with consistent monitoring, have helped eliminate some instances of the invasive weed and is moderately successful. If your invasion of Johnsongrass is bad, then call a lawn service.