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Planting asparagus

Quick facts

  • Asparagus spears are the part of the plant that goes to harvest but the ferns, crowns and seeds are just as important.
  • Select the right variety of asparagus for Minnesota's climate.
  • Consider soil drainage, sunlight, soil texture, irrigation and soil pH when choosing a planting site.
  • Following the steps outlined in planting a new asparagus crop will help ensure that your investment pays off.
Asparagus spears

Asparagus is a high-value perennial crop and plants can live and produce for more than 15 years in Minnesota. Although commercial production in the United States is concentrated in California, Washington and Michigan, Minnesota's climate and soils provide an excellent environment for growing asparagus.  The demand for this crop is higher than the current in-state production.

Asparagus is the earliest crop to market, and growers can market it to restaurants, at farmers' markets, and through community-supported agriculture (CSAs) and roadside stands.

The cost to establish an asparagus field is substantial, so growers should have a robust management plan in place before planting. 

How asparagus grows

Asparagus spears emerge each spring from underground buds. After the harvest season ends in late June, additional spears are allowed to grow into ferns that photosynthesize and accumulate carbohydrates that the plant uses to keep growing the following year. The plants are dormant from December to April in Minnesota and many varieties are known to overwinter well in our climate.

Spears

The edible part of the asparagus plant is called the spear.

  • Spears are the newly emerged stems of the plant.
  • Spears continually emerge from the underground buds on the crown of the plant for several weeks in the spring and summer.

Ferns

Fully grown asparagus ferns in field.
Fully grown asparagus ferns

Spears that are not harvested will keep growing and turn into ferns. This happens at the end of each harvest season, and in newly planted asparagus stands that are not harvested.

  • Ferns are an important part of asparagus production.
  • They photosynthesize for several months following the spear harvest season, transporting energy to the crowns for storage over the winter.
  • Healthier ferns give way to healthier plants and higher yields in subsequent years. 

Crowns

The crown is the belowground part of the asparagus plant that includes roots, rhizomes and buds.

  • The spears grow off of the buds during the growing season.
  • During the dormant season (winter) the crowns store energy in the form of carbohydrates that allow the plant to keep growing from year to year.
  • New asparagus fields are typically planted from small crowns, rather than planting them from seed.

Seeds

  • Female plants produce small black seeds that can become weedy volunteer asparagus.
  • Open-pollinated varieties of asparagus contain both male and female plants.
  • Hybrid varieties are mostly all-male plants, so planting hybrids minimizes the issue of re-seeding.

Recommended asparagus varieties for Minnesota

Asparagus crown

Most asparagus growers plant hybrid varieties for their superior yields, uniform spear size, disease resistance and all-male plants. Open-pollinated varieties are also widely available at a lower cost per crown than the hybrid varieties. The yield of open-pollinated varieties is generally lower, and the size and quality of the spears is more variable.

Hybrid varieties for Minnesota

  • Millennium 
  • Jersey Knight
  • Jersey Giant
  • Jersey Supreme

Open-pollinated varieties for Minnesota

  • Mary Washington
  • Martha Washington
  • Purple Passion

Choosing a planting site for asparagus

Since asparagus is a long-lived perennial crop, proper site selection is important. While annual vegetable crops can be moved if the first planting site doesn’t work, asparagus cannot.

Site requirements for asparagus include:

  • Good soil drainage. Do not plant in heavy or wet soil where water pools.
  • Full sunlight.
  • Medium textured soils (silt loam, loam, sandy clay loam, sandy loam). Avoid planting in heavy clay or very sandy soil.
  • Access to irrigation, particularly in the planting year (especially important for sandy soils).
  • Soil pH ideally between 6.5-7.0. Soils with a pH slightly above or below are not ideal, but can still be suitable for asparagus with liming or other amendments.

In addition to soil quality, the slope of the land also impacts soil water drainage. We recommend planting asparagus on a slight slope is recommended especially when heavier soils are present. Avoid planting asparagus in heavy clay soil.

Planting a new asparagus field

Following correct planting methods for asparagus is important for this long-lived perennial crop. Planting mistakes are costly because they can impact yield and crop health for years to come.

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Annie Klodd, Vince Fritz, Cindy Tong and Natalie Hoidal, Extension horticulture educators

Reviewed in 2020

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