The best way to convert a lawn into a garden does not employ a shovel or a sod cutter and will save wear and tear on back muscles. Sheet mulching—a simple technique that involves layering cardboard, compost, and other organic material right over the turf—kills the grass and leaves behind beds with rich soil. A considerable amount of organic debris goes into the bed construction, so stockpile plenty of autumn leaves, composted manure, and garden waste before beginning. Beds that are sheet-mulched in the fall will be ready to plant the following spring.
Use spray paint or powdered lime to mark the perimeter of the new bed. Scalp the grass within the outline with a lawn mower.
Spread a 2-inch layer of compost or composted manure over the bed. This helps encourage microbial activity in the soil and speeds decomposition. Moisten the compost well.
Cover the compost with overlapping pieces of cardboard to smother the underlying vegetation and prevent light from reaching any weed seeds. Soak the cardboard with water.
Spread a 2-inch layer of compost over the cardboard and top it with up to 18 inches of mixed organic material (grass clippings, leaves, straw, seaweed, garden debris, farmyard manure).
Include vegetable and fruit scraps and coffee grounds from the kitchen in the layers of organic matter. Moisten these layers.
For vegetable beds, finish with 2 to 3 inches of straw or compost. Top ornamental beds with 4 inches of wood chips. In arid climates, water the bed occasionally. Soil microbes and earthworms will toil through the winter to decompose the organic material, cardboard, and sod.