Johnsongrass is a perennial that reproduces from horizontal root as well as seed. Idaho's cold winters are usually no match for this noxious weed, causing it to exhibit growth characteristics of an annual plant. Leaves are grasslike, up to one inch wide with a prominent whitish midvein. The plant may grow from 2 to 8 feet tall. This noxious weed can be found growing in almost any situation. It was originally introduced as a forage crop; however, toxic levels of cyanide are produced when the weed is damaged by wilt, trampling, or frost.

Control

Preventing Johnsongrass from becoming established in new areas is the best available control method. To reduce an infestation with herbicide, it is necessary to use an integrated approach consisting of soil-applied herbicides, post-emergence herbicides, crop rotation, and/or tillage. Planting desirable vegetation should also be considered.

Johnsongrass control programs should prevent spread of rhizomes and seed from infested to uninfested areas. Kill or weaken established plants and their underground rhizome system. Control seedlings originating from shattered seed. Use fall tillage to bring rhizomes to soil surface, where they may be killed by winter conditions.

When choosing any kind of control method, assure that your choice is suited for your particular situation. Always read and follow the product label before applying any herbicide.