The Burpee company sells asparagus seeds and provides guidance on their successful germination and cultivation into mature, bearing plants. Asparagus seeds germinate and mature into harvest-ready plants in three years' time, according to Burpee. While growing asparagus from established crowns is a quicker route by roughly a year, starting by seed is preferred for larger crops and as a cost-saving measure.
Start your Burpee asparagus seeds indoors in a seed tray or in small pots 12 to 14 weeks before planting in the garden soil in spring after the last frost has passed. Bury the seeds 1/4-inch deep in sterile potting mix, and water the seeds until the soil is drenched. Keep the soil moist at all times. Place in a sunny location for three weeks until the seeds germinate. Harden off the seedlings for a week in an unheated cold frame or greenhouse before placing into the garden soil.
Plan to plant your asparagus seedlings outdoors in a location with a minimum of six to eight hours of full sun exposure daily. Asparagus can tolerate partial daily shade, but this may reduce the crop size slightly. Choose a portion of the garden where no vegetables or flowers have previously been grown to prevent related soil diseases from attacking the crop.
Provide a sandy, loamy soil with excellent drainage but enough water-holding organic material to keep the soil moist at all times. Ensure that the planting soil is barely acidic to neutral ranging between 6.5 and 7.0 pH. If in doubt, conduct a soil test and amend the soil as necessary with lime or sulfur to bring it into the desirable range.
Mix a dose of 5-10-10 fertilizer into the planting soil before setting out the seedlings in the spring. Use 1 to 2 lbs. of fertilizer for every 100 square feet of asparagus plantings. Till the fertilizer into the soil well to distribute evenly in the top few inches of soil.
Dig a small hole for the seedling plant root mass and surrounding soil. Plant at the same depth as in the previous container. Space the plants at intervals of 10 to 12 inches. Tamp soil around the roots lightly and water until the surrounding soil is drenched.
Mulch around the base of seedlings and between plants with 4 to 6 inches of lightweight chipped leaves or straw to insulate the seedlings from temperature fluctuations, hold moisture in and keep weeds down.