Asparagus: Plant once, harvest for 20 years or more
The tasty spears of this perennial are an excellent source of folate (needed for strong immunity) and a good source of vitamin C. A 1/2-cup serving contains just 22 calories.
Plant 12-18 inches apart in spring or fall. Prepare an 18-inch trench filled with 6 inches of compost followed by 6 inches of rich topsoil. Spread the crowns over the soil and cover them with 2 inches of soil. Gradually fill the trench with soil as the plants grow. If planting in fall, fill the trench completely. Each spring, apply 3-5 pounds of fertilizer per 100 square feet. Work into the soil before growth starts. Repeat application after the harvest is complete.
Cut the tops back and mulch in late fall to help prevent deep freezing and sudden changes in soil temperature. Limit the first harvest to one or two cuttings by mid-June of the second year. A full crop can be harvested the third year after planting, when the spears are 6-10 inches tall. (If planting 2-year crowns, you should harvest a good supply the second year.) Harvest for 6-8 weeks only, or until about the first of July in the North. When harvesting, snap off or cut spears at ground level to avoid injuring new growth.