Conduct a soil test of the area where the asparagus will be grown. Test six months before the late winter planting to ensure ample time to amend soils or correct problems. Soil test analysis takes about two to three weeks, and a county cooperative extension office has information and resources to conduct the test.
Build up organic matter at the planting site. Add 8 to 12 inches of compost, leaf mold or well-rotted manure. Dig it into the garden soil with a shovel, pulverizing any soil clumps to create a soft, loose-textured soil. Add the organic matter starting in fall and across winter as long as the soil isn't frozen. Continually mix it into the planting area.
Plant the asparagus crowns in late winter to very early spring in rows spaced 5 feet apart. Plant the crowns 10 to 12 inches apart in the row. The tops of the crowns, from where the growth buds appear, should be covered in 2 inches of soil. Spread the roots out evenly and widely in the furrow. Take care not to break the roots.
Water the asparagus plants as needed to keep the soil evenly moist, but never dry or soggy. Supplement natural rainfall across the growing season.
Weed around the asparagus plants, pulling them out by hand before they get too large. Avoid using a hoe to severe the rather shallow matrix of asparagus roots. Consider laying a 3-inch layer of organic mulch in the bed to discourage weeds, but keep the mulch pulled back from the asparagus by 4 to 5 inches.
Fertilize the asparagus in subsequent springs. Scatter 2 to 5 lbs. of a 5-10-10 granular fertilizer on 100 square feet of bed. The first applications must occur in early spring before any spears break the soil surface. Do a similar second application after harvesting spears ends in late spring. Top-dressing the planting bed with compost or fresh organic mulch can be done anytime of year to keep the soil fertile.
Cut away the frost-killed stems in early winter once they are fully brown and dried. Make the pruning cuts 3 inches above the soil line. The stumps will decay over the winter.