What to do now
Mildest step first.
- Test the soil before planting and add lime if it is acidic; aim for a pH of about 6.5.
- Dig a trench 6 inches deep in heavy soil or 8 inches in sandy soil, and set the crowns 12–18 inches apart with roots spread and buds up.
- Cover with 2 inches of soil, then add more as the spears grow, keeping the tips uncovered, until the trench is level.
- Don't cut any spears the first year; let them grow into ferns.
Not sure this is it? Check other asparagus problems
When to plant
Plant crowns in early spring, as soon as the ground can be worked. Oregon State puts this at about 3 to 4 weeks before the . Plant soon after you buy them: Clemson warns that crowns kept too long start to sprout, which can damage the buds. An asparagus bed can produce for many years, so choose a sunny spot you won't need for anything else. All-male varieties such as 'Jersey Giant' and 'Jersey Knight' yield much more than older types like 'Martha Washington', which have many female plants. Clemson says the newer all-male outproduce the old cultivars 3 to 1.
Trench and spacing
Iowa State suggests planting crowns 6 to 8 inches deep in heavier soils and 8 to 10 inches deep in light, sandy soils. Illinois calls for a trench about 12 to 18 inches wide and a full 6 inches deep, and Clemson gives 6 to 8 inches. Spacing varies more: Illinois says 9 to 12 inches apart, Oregon State and Utah State 12 inches, Iowa State 12 to 18 inches, and Clemson 15 to 18 inches. Leave about 4 to 5 feet between rows. Spread the roots out in the trench with the buds facing up.
Filling the trench
Most sources say to cover the crowns with about 2 inches of soil at first. As the spears grow, keep pulling soil into the trench, leaving the tips uncovered, until it is level with the ground by the end of the first summer. Iowa State, however, says it is not necessary to fill the trench gradually and that it can be filled all at once at planting. Either way, do not bury ferns that are already growing.
Soil and pH
Asparagus does best in deep, well-drained soil, and it dislikes acid soil. Sources give somewhat different targets: Oregon State recommends about 6.5 to 7.5, and Clemson recommends 6.0 to 6.5. A pH around 6.5 suits both. Test the soil first, and if lime is needed, Clemson suggests adding it at least three months before planting, so the fall before is a good time.
When you can harvest
Don't harvest at all in the planting year. After that, sources differ. Oregon State allows a light harvest of 1 to 2 weeks in the second year, while Iowa State, Illinois and Utah State say to wait until the third year. Utah State suggests up to 4 weeks of harvest in the third year, 6 weeks in the fourth, and up to 8 weeks once the plants are five years old. Stop for the season when most new spears are thinner than a pencil, or by mid-June in most areas, and let the rest grow into ferns to feed the crowns for next year.
Growing it again? When to plant asparagus for your ZIP code
- When and how should I adjust my soil pH, and how long does it take to work?pH amendments work slowly — lime often takes a few months and elemental sulfur several months to a year to shift pH — so apply them in fall or as far ahead of planting as you can, not at planting time, and retest before adding more.
- When is the best time to add compost to the garden?Fall is a good time to add compost to garden beds — it has all winter to incorporate and break down further, and beds are ready to plant without delay in spring.
- What soil should I put in a raised bed?Fill a raised bed with topsoil and compost, about 2 parts topsoil to 1 part compost (or half and half). On pavement, use compost and a soilless mix 1:1. Bagged mixes work but cost more, and every fill settles.
- What soil temperature do I need to plant vegetables?It depends on the crop. Lettuce, spinach and onion seeds can sprout in soil as cold as 35°F. Peas, carrots, beets, radishes, cabbage and kale need about 40°F, potatoes 45°F, and corn and tomatoes 50°F. Beans, cucumbers, peppers, squash and melons need 60°F. Seeds come up faster and more evenly when the soil is well above these minimums.