HOW TO PLANT ASPARAGUS First, make a trench about 8 inches deep in soil with good drainage and plenty of sun. Add organic matter and a high-phosphorus fertilizer into the bottom of the trench. Asparagus plants are heavy feeders and will stay in the same soil for many years. Space plants about 18 inches apart in the row. Cover the crowns with soil and water moderately to settle the soil and eliminate air pockets. Gradually fill in the trench as the young plants grow. Do not harvest any spears the first year after planting.