An asparagus bed can remain productive for many years after it is established. Since asparagus spears grow into tall plants with fern-like growth, they can shade out other plants, so correct location of a permanent asparagus bed is important. Male asparagus plants produce the most numerous high quality spears in early spring and all-male crowns are now available. The male varieties available for home gardens are Jersey Knight, Jersey Giant and Jersey Prince. Asparagus grows best in well-drained soil with a pH between 6.5 and 7.5.
Locate an area in the garden that receives at least six hours of sun per day and is appropriate for a permanent asparagus bed. Asparagus beds can remain productive for 15 to 20 years or longer. If possible, find a location that is away from grassy areas where weeds can spread to the bed. Weeds and grasses consume nutrients and moisture the asparagus plants need to remain healthy throughout the season. Tall and healthy asparagus plants produce the best spears in the spring.
Prepare the planting area by loosening the soil with a shovel to a depth of 16 inches. Spread a 1-inch layer of well-rotted compost over the bed and gently work into the top 3 inches of soil with a hoe. The best time to do this is in the fall if you are planting asparagus crowns in the southern U.S. In northern areas, where the ground freezes, prepare the bed in the spring as soon as the ground can be worked. The crowns are spaced 18 inches apart, so make the bed large enough to accommodate the number of crowns you have available.
Dig a trench 6 inches deep that is long enough to accommodate the number of crowns. Add a 1-inch layer of well-rotted compost to the bottom of the trench.
Set the crowns into the trench at 18 inches apart. However, the bottom center of the crowns should be elevated with the pencil-sized roots pointing downward. To position the crown correctly, make a lump of soil 2 inches high under each crown with one hand and set the crown on top of the lump of soil with the other. Gently push the crown into the lump of soil so the bottom of the crown and the roots have contact with the soil.
Cover the crowns with 2 inches of soil. Completely fill the trench by adding soil around the ferns while they are actively growing during the summer. When the first spears appear in the spring, do not harvest. You will not harvest until the second year to allow the plants to get established. Cut the ferns to the ground when they die in late fall or winter and add a 1-inch layer of compost over the dormant crowns before spring.