When & How Do You Plant Asparagus in Western Washington?

Western Washington Growing Zones

• Western Washington State extends from the Cascade Mountains to the Pacific Coast and includes the Seattle metro area and the Olympic Peninsula. Growing zones extend from USDA zones 6a in the mountain regions, to zones 9a around the coastal areas. Plant asparagus in spring, when the soil warms to 50 degrees Fahrenheit and is easy to work. In the mild areas around the coast, you can start asparagus in early spring. Measure the soil temperature by inserting a soil thermometer into the top 4 inches of the planting area to get a correct temperature reading.

Growing Conditions and Soil Preparation

• Damp soil conditions in Western Washington create a challenge for growing asparagus. Plant asparagus in an area that drains well in part to full sun, or four to six hours of sun per day. Avoid low spots or any area where water pools during the wet season. Using a raised bed will help improve drainage in damp areas. Prepare the soil by adding a 4-inch-deep layer of compost or manure to the bed and then dig it into the top 12 inches of the soil.

Planting Asparagus

• Plant asparagus from 1-year-old crowns, or root sections. While you can grow asparagus from seed, you will be waiting three years to harvest. By planting crowns you can start harvesting in the second year. Plant asparagus crowns 4 inches deep in 10-inch-wide furrows and space each crown 10 to 12 inches apart along the row. This shallow planting depth will help prevent the roots from getting waterlogged in the damp soil commonly present in Western Washington. In drier areas, asparagus is typically planted as deep as 12 inches. After setting the crowns in the soil, push 2 inches of soil over the roots.

After Planting Care

• Keep the asparagus bed moist but not wet. Water when the top 1 inch of soil feels dry. As the asparagus stalks grow and develop height through the first growing season, add lightweight soil gradually to the base of the plants until you have a mound 3 to 4 inches tall. Two pests to watch out for are asparagus beetles and pear psylla. Check plants regularly and pick off and destroy any insects you find.