Asparagus is a long-lived perennial vegetable, offering decades of spring harvests from a single planting. Establishing a successful patch requires specific attention to timing, especially in a cold climate like Wisconsin. The state’s harsh winters and shorter growing season necessitate precise planting to ensure the crowns establish a robust root system before the first hard freeze. This guidance focuses on planting one-year-old crowns, the standard method for home gardeners.
Determining the Ideal Planting Window in Wisconsin
Plant asparagus crowns in Wisconsin in early spring, immediately after the ground thaws but before summer heat arrives. This period is usually late March to early May, shifting based on whether you are in southern or northern regions. The goal is to place dormant crowns in moist, cool soil, allowing root growth to begin before the plant focuses energy on spear production.
A reliable indicator is soil temperature, which should reach approximately 50°F before crown installation. This temperature ensures crowns break dormancy and begin growth without risking damage from a late frost. Early planting maximizes first-year growth, dedicated entirely to developing the underground root mass that fuels future harvests.
Fall planting is discouraged in cold climates like Wisconsin due to the high risk of frost heave. Crowns planted in fall lack the established root system needed to anchor them securely, making them vulnerable to being pushed out by repeated freezing and thawing cycles. Spring planting avoids this risk, allowing crowns an entire mild season to set deep roots.
Selecting Cold-Hardy Varieties and Preparing the Planting Site
Selecting the right variety is important for a long-term, high-yielding asparagus bed in Wisconsin. Male hybrid varieties are recommended because they produce no seeds, dedicating all energy to spear production, resulting in higher yields. Cultivars such as ‘Jersey Knight,’ ‘Jersey Giant,’ and ‘Jersey Supreme’ are bred for cold hardiness and are excellent choices for the Upper Midwest.
Asparagus requires a permanent location that receives full sun, meaning at least six to eight hours of direct sunlight daily, to support crown development. The site must also have exceptional drainage, as the fleshy crowns are susceptible to rot if they sit in standing water during the winter thaw or wet spring periods. If the area has heavy clay soil, a raised bed or mounded rows may be necessary to ensure water quickly moves away.
Proper soil preparation should begin well before planting, as the bed will remain in place for decades. Asparagus thrives in a soil pH between 6.5 and 7.5; a soil test determines if lime or sulfur amendments are needed. Before digging the trench, incorporate generous amounts of aged organic material, such as compost or manure, to a depth of at least 12 inches to improve structure and fertility.
Step-by-Step Planting Process for Asparagus Crowns
The planting process involves creating a trench that facilitates deep root growth and allows for gradual soil coverage. Begin by digging a trench 6 to 8 inches deep and 12 inches wide down the center of the prepared bed. This depth protects the crowns and encourages a deep root system.
Next, create a low, cone-shaped mound of soil at the bottom of the trench every 12 to 18 inches for each crown. Place a one-year-old crown on top of the mound, carefully spreading its long, fleshy roots uniformly along the trench bottom like spokes of a wheel. The central bud should rest slightly above the surrounding roots.
Cover the planted crown with only 2 inches of soil, leaving the trench mostly unfilled. As the first spears emerge and grow into fern-like foliage, gradually add more soil throughout the first growing season. This sequential backfilling ensures the crowns settle deep enough for long-term health while preventing the emerging spears from being smothered.
Essential Care and Harvesting Patience for the First Three Seasons
The first two years after planting are focused entirely on root establishment, and no harvesting is allowed. Throughout the first and second growing seasons, spears must be allowed to grow completely into mature, fern-like foliage. This fern growth is the plant’s photosynthetic engine, capturing sunlight to produce sugars stored in the crowns for the following spring’s harvest.
Weed control is important during these early years, as asparagus does not compete well for water and nutrients. Shallow cultivation or a thick layer of mulch helps suppress weeds without damaging developing roots. Consistent watering is necessary during dry spells to ensure uninterrupted root and fern growth for long-term productivity.
The first harvest begins in the third spring, but it must be limited to four to six weeks to avoid overstressing the mature crowns. Harvest spears when they are 8 to 10 inches tall by snapping them off at the soil line or cutting them just below the surface. Once the limited harvest period is over, all remaining spears must grow into ferns to replenish energy stores for the next year.