Grass is not always welcome in a garden. If you have landscaped areas, vegetables, flower beds or paths, you do not generally want grass popping up. It takes nutrients away from other plants, and may be unsightly. There are several ways to kill grass in your garden, depending on where it is located and what is planted nearby.
Spread large areas of grass with black garbage bags and put rocks over the bags to hold them down. This will kill the grass by blocking out light. Leave the bags in place for at least a week to make sure all of the grass dies.
Pull small clumps of grass out by the roots to prevent spread. Do this especially around vegetable gardens, so you don't have to spray chemicals near your produce.
Spray paths that aren't near plants with an herbicide or vinegar. Large quantities of vinegar will kill weeds and grass, and general herbicides kill grasses as well. Use a selective herbicide if you are working around flowers and plants.