Add black plastic mulch to your spring soil preparation schedule. Dig into and amend the soil first, since you won't have access after you put the plastic down. Dig up the top 6 to 10 inches of soil to break the soil and aerate it.
Lay 3 to 5 inches of sod compost or general organic compost on top of the site. Use a garden fork to turn the compost into your tilled soil to give the garden a rich, fertile and moist growing foundation. Add 1 lb. of 13-13-13 fertilizer per 100 square feet, and turn the fertilizer into the top 4 inches of soil. Water the site for half an hour to help the soil and fertilizer settle, and to prepare the soil for planting.
Roll your black plastic strips out over the site and cut them to fit. Use rocks, bricks or landscape staples to secure the strips of plastic at their edges and ends.
Cut the plastic mulch with a knife or scissors for planting. Create 3- to 5-inch strips for the plants. Use plant-specific guidelines for spacing.