Asparagus is a long-lived perennial vegetable, producing at least 15 years in a garden. Although it can be grown from seed, it's tedious, and gardeners often purchase 1-year-old crowns of plants from plant nurseries. Plant the crowns when they're dormant and no growth has started. Gardeners in the western mountains and Piedmont plant asparagus in very late winter when hard freezes no longer occur. In eastern counties, plant in mid-February. Asparagus needs a full-sun exposure in a well-drained soil rich in organic matter for best growth.
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.
Things You Will Need
- For ample crops and subsequent meal portions, plant 10 crowns for every family member of the household.
- Heavy soils, such as the clay of the Piedmont region, must be deeply dug and amended with lots of organic matter to improve drainage and make the soil softer and easier for the asparagus spears to grow through.
- Asparagus grows poorly in acidic soils. Amend the garden soil with lime or create a raised berm of neutral-pH topsoil. The ideal pH range is 6.0 to 6.7.
- The best varieties of asparagus plants to grow in North Carolina are Martha Washington, Jersey Giant, Jersey Supreme and Jersey King.
- For the first two years after planting the asparagus crowns, do not harvest any spears in spring. This allows the plants and roots to establish well and become vigorous so by the third spring after planting they can withstand spear harvesting for six to eight weeks in spring for many years.
- Harvest spears until Memorial Day. Thereafter, allow the plants to grow with leaves so the roots can rejuvenate and grow to be healthy for next spring's crops. Over-harvesting weakens plants.