Growing premium asparagus in Minnesota is another successful collaborative effort between the Sustainable Farming Association of Minnesota and the U of MN Extension. SFA’s Asparagus Project has been introduced to farmers and curious gardeners across the state in eight presentations so far this year, led by Annie Klodd, of the U of M Fruit and Vegetable Production department. I had the pleasure of attending a classroom-style education session, hosted by the East Central SFA chapter, and now feel more confident about beginning my own plot of asparagus next spring.
Minnesota farmers and gardeners can benefit from adding an asparagus bed, both financially and nutritionally. This hardy perennial joins rhubarb in the spring as one of the first fresh crops to mature in our zone with minimal input from the grower after the first couple of years. Asparagus is a delicious addition to the menu and coveted springtime ingredient of local chefs. The plant gets better with age, as a well maintained plot will be more productive later on in its lifespan of fifteen years or more. We learned that the going rate is $5/pound in the Twin Cities market, and the demand is quite high in our state for local sources. Yields have been as high as 800-1,600 pounds/acre in organic systems with weed pressure in Minnesota, conventional growers harvesting 1000-6,000 pounds/acre.
Getting started with asparagus can be as intensive or minimalist as the grower prefers; establishing a minimum of 1/5-acre plot is a good baseline for those who plan to bring the crop to market. The plants don’t require regular tillage or specific soil type, and their main insect foe, the asparagus beetle, can be easily dealt with by removing the dead ferns in autumn. They can be grown from seed but will take over 3 years to reach production size. For this reason, most growers choose to purchase 2-year-old roots called “crowns,” which can be ordered in the winter and shipped to your property in mid April. It’s best not to get them shipped earlier, as they must be refrigerated until planting time.
Asparagus comes in open pollinated and hybrid, and each has its benefits. Open pollinated produce less uniform spears, and will produce seeds, lots of them. These seeds produce many smaller plants amid the mature asparagus, which compete for nutrients and increase the variety of spear sizes. These older varieties, including Mary Washington, Martha Washington, and Purple Passion, may be more disease resistant, hardy and are cheaper to purchase; however, they do take longer to reach market size with smaller yields overall. Hybrids will not reseed, make consistent spears, but are not as long lived as open pollinated. Growers have had good results with hybrid asparagus in Minnesota, and the varieties are similar in name (Jersey Giant, Jersey Knight, Jersey Supreme).
Preparing the plot this year can set one up for a productive planting next spring. Get a soil test sample from the site and send to either the U of M Soil Testing Lab or Midwest Labs. Feel free to reach out to the SFA Asparagus Project if you need help interpreting the results. Fertile, well-drained soil is the key to success along with removing any aggressive perennial weeds/grasses that could compete with nutrients (thistles and quack grass are two of the worst offenders). Tilling can be utilized to prep a field full of hardy weeds, and used billboard tarps can also be used to cover the plot a few months before planting, burning out competing plants. Smother crops of rye or buckwheat can also be used the season before along with tillage radish or other crops that nourish and break up soil.
Once the asparagus crowns are planted, have a plan for keeping weeds out of the rows; mulching can be effective. Cultivation or heavy mulch between the rows will reduce weed pressure, and many growers use this space to plant cover crops of all kinds. These can be mowed down regularly during harvest season to create footpaths, and small crops of lettuce or compact annuals can be planted between rows after June.
Part of the Minnesota Asparagus Project goals are to assess the production of different varieties along with noting interesting practices among Minnesota growers. If you decide to grow asparagus and plant pumpkins between the rows, for example, SFA would appreciate learning about your experience. You can also learn more at the next project event in Marine on St. Croix at Big River Farms. Register on the Sustainable Farming Association webpage for the asparagus project.