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.

Yellow leaves and stems on your sprouts indicate they’re not getting enough light. Keep them near the appropriate light source and give them as much as they need (they require longer exposure to fluorescence than they do to natural light sources).

Vinegar is known to be a contact herbicide, which means it kills the foliage it comes in contact with. Because of the high acetic acid concentration, horticultural vinegar kills weeds and grass more effectively. However, keep in mind that high amounts and multiple applications can affect the soil by lowering the pH levels.

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.