Answer: There are several ways to start a garden in a lawn area. You do have to remove the existing grass. You can remove it using a sod cutter machine to strip it off (rent one for a day), dig it out by hand (doable if it is a small area), kill it with an herbicide containing glyphosate (read and follow label directions), or smother it under a layer of damp newspaper topped with mulch (if you do this, wait until the grass is dead and then till it under, paper, mulch and all.)
Be sure to compost the sod if you remove it -- you do not want to lose the topsoil held by its roots. Tilling can be done to loosen the soil after the sod is removed. Some gardeners will begin a new garden by simply tilling the sod under. This works but can result in tufts of sod at the soil surface that will continue to grow. If you do this, plan on tilling again in a few weeks to disturb these. All of these methods will work and can be done now.
You would also want to run some basic soil tests to check fertility and pH. Follow the test results as to adding limestone to adjust the pH as needed. Fall is a good time to add it so it has time to leach naturally down into the soil, or add it when you turn the soil so it is mixed through the root zone. Wait to add fertilizer until you are getting ready to plant.
When you prepare the garden area, loosen the soil down about ten inches and work in several inches of organic matter such as compost or chopped autumn leaves or whatever you have available. Level the area and rake the surface smooth prior to planting.
If you prepare the garden in the fall, mulch it over the winter to prevent erosion of the bare soil. Use an organic mulch and plan on digging it under in the spring as an additional source of organic material. In spring, you would need only to spade it lightly to prepare for planting.
Good luck with your project!
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