Asparagus is a long-lived perennial vegetable grown for its tender spring spears. A well-tended bed produces for 15 to 20 years, so it is worth siting permanently in full sun, in deeply worked soil that drains, where it will not be disturbed by annual tilling.
Plant one-year-old crowns in early spring, in a trench 6 to 8 inches deep with the roots spread over a mound, 12 to 18 inches apart, and fill the trench in gradually as the spears grow. Do not harvest the first year and take only a few spears the second, so the root system builds. From the third year cut every spear over pencil thickness for six to eight weeks, then stop and let the fern grow all season to feed the crowns; cut it down only after it yellows in fall. All-male hybrids outproduce the old open-pollinated types because they put nothing into seed.
The fern reaches 4 to 5 feet and is a fine backdrop. Asparagus beetles chew the spears and fern from late spring; pick them off, and clear the old fern in fall where they overwinter. Keep the bed weeded and mulched, and top-dress with compost each spring. Deer leave it alone.
Rust
Orange to brown raised pustules on the undersides of leaves, with yellow spotting on the upper surface. Heavy infections cause leaves to yellow and drop.
Remove and destroy infected leaves. Avoid overhead watering and improve air circulation. Apply a sulfur or copper-based fungicide if it spreads. Clear plant debris in fall.
Fusarium wilt
Sudden wilting, brown streaks in stems, yellowing leaves. Affects sweet basil varieties most.
No cure. Remove and destroy plants. Do not replant in the same spot for 3+ years. Choose resistant varieties.
Asparagus Beetle
Crioceris asparagi →Blue-black or spotted beetles feed on spears, leaving brown scarring and bent tips. Dark eggs stand upright on spears and ferns; larvae defoliate the fronds.
Handpick adults and larvae and crush eggs. Keep the bed clean of debris where beetles overwinter. Harvest spears promptly and use spinosad or neem if populations are heavy.