Asparagus is one of the most popular vegetables in spring. If planted in a favorable site and given proper care, an asparagus planting should produce good crops for 15 to 20 years.
Since asparagus is a perennial crop, carefully consider possible planting sites. Asparagus performs best in well-drained soils in full sun. Planting sites should receive at least 6 hours of direct sun each day. Avoid shady sites near large trees and buildings. Raised beds are a good planting option for gardeners with poorly drained soils.
Asparagus is dioecious. Dioecious plants produce separate male and female plants. Male asparagus plants live longer and are more productive than female plants. Excellent all-male asparagus varieties (cultivars) for the home garden include 'Jersey Giant,' 'Jersey Knight,' 'Jersey King,' and 'Jersey Supreme.' 'Mary Washington' and 'Martha Washington' are good standard asparagus cultivars. (A planting of 'Mary Washington' or 'Martha Washington' will include both male and female plants.) 'Purple Passion' is a distinctive cultivar with purple spears.
Early spring (April) is the best time to plant asparagus in Iowa. Asparagus crowns should be planted in shallow trenches or furrows. The planting depth depends on the soil type. Asparagus crowns should be planted 6 to 8 inches deep in light, sandy soils, but only 4 to 6 inches deep in heavier soils. A small amount of well-rotted barnyard manure can be worked into the soil at the bottom of the trench before planting. Space crowns 12 to 18 inches apart in rows that are 4 to 5 feet apart. Spread the roots out in the trench with the buds pointing upward. After planting, completely fill in the trench with soil. (Though commonly done in the past, it's not necessary to gradually fill in the furrow as the plants grow.)
Asparagus plants should be allowed to become well established before any spears are harvested. No spears should be harvested during the first growing season. Asparagus can be harvested over a three to four week period during its second growing season. In following years, asparagus plantings can be harvested until early to mid-June. Harvest asparagus by cutting or snapping the spears when they reach a height of 6 to 8 inches.