Creating a new garden bed involves removing everything from the garden plot. Killing existing grass presents a challenge because grass throws deep roots into the topsoil. These tenacious roots make removal of grass as difficult as removing stubborn weeds. Plenty of options exist to kill grass to make a garden. These include the use of herbicides, digging up the grass and killing the grass by solarization. Choosing a method depends on the amount of time available before planting.
Mark the outline of your garden area with a hose. Designating this area clearly will help prevent killing nearby grassy areas that you'd like to preserve.
Spray a herbicide such as Roundup that contains glyphosate to kill grass during active growth only. The grass will discolor and eventually die over the next few weeks.
Use the spade to dig down at least 6 inches to remove all dead grass clumps as well as weeds from the garden area. Grass can be exceptionally stubborn to remove since the root system can travel more than 6 inches beneath the soil surface.
Monitor the garden area for a few weeks and apply additional herbicide in trouble spots.
Start at the front of your proposed garden bed and drive the spade shovel deeply into the soil to a depth of at least 6 inches.
Lift up the entire clump of grass and shake off excess dirt. Place the clump into a wheelbarrow for transplanting elsewhere or discard the grass in the compost pile.
Continue digging up the entire garden to remove all traces of grass.
Schedule your attempt to kill the grass for early summer. Water the grassy area before applying any plastic sheeting to the ground. Grass and soil should be damp to the touch.
Lay a single layer of thick clear plastic on top of the grass. The clear plastic attracts considerable heat to kill the grass.
Secure the corners of the plastic sheeting by driving plant stakes into the corner to hold the plastic sheeting. Use rocks to secure and loose areas of the plastic. Remember that you don't want the plastic to be disturbed by wind, weather, humans or animals.
Allow the plastic sheeting to sit in place for eight to 10 weeks to kill the grass. Temperatures under the plastic will be hot enough to burn the grass and roots.