Glyphosate and other non-selective herbicides can kill orchard grass, but they will also kill the surrounding plants. Also, not all areas allow the use of glyphosate due to its environmental impact—which the EPA describes as a "potential risk to terrestrial and aquatic plants and birds, and low toxicity to honeybees." Consider mechanical removal to target the plants specifically.

The fastest ways to kill weeds and unwanted grass include burning them, pouring boiling water on them, or pulling them out by hand, as these methods work almost instantaneously. For a quick-acting solution that works within a few hours, you can use a commercial-grade herbicide like glyphosate or a DIY vinegar, salt, and dish soap mixture. While effective, be aware that commercial herbicides introduce chemicals into your lawn. The slowest method for killing weeds is to starve them of sunlight and nutrients using mulch or fabric covers.

There are organic herbicide options that will kill grass but not flowers, including white vinegar or a dish soap solution. Commercial selective herbicides can also target grass over other plants, but read the instructions carefully to avoid damaging your garden. Herbicides that kill grass but not flowers usually include ingredients like clethodim and sethoxydim. Otherwise, your best bet will be to weed by hand.

Mowing your grass regularly, especially if you’re mowing close to the ground, can help kill Johnsongrass. Frequent mowing helps limit the spread of Johnsongrass and can even deplete carbohydrate reserves in rhizomes over time. The more time you leave in between mowing, the more likely Johnsongrass is to regrow and take over your lawn.