1. Asparagus (Asparagus officinalis) is a perennial vegetable that is easily grown on the prairies.
  2. As a perennial vegetable, asparagus needs a permanent spot in the vegetable garden.
  3. Do not harvest asparagus spears from new patches for the first three years to give the plants time to establish a robust, healthy root system.
  4. Although it takes several years to establish an asparagus patch, established patches can be productive for several decades to come. 
  5. The key to a successful asparagus patch is planting into light soil (sandy loam to loam) with good fertility and choosing the right cultivar. 

Asparagus is high in vitamins A,C,E, K, folate, riboflavin, thiamine and fibre. Check here for detailed information from the USDA National Nutrient Database for Standard Reference.

The Canadian Food Guide recommends that roughly half of the food on your plate should be fruits and vegetables.

Canada Food Guide: What's On Your Plate?

Growing outdoors

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Asparagus needs full to partial sun for best growth. Asparagus is not suitable for partial shade or shady areas. Since asparagus is a long-lived perennial vegetable, choose a site that won't become shaded by nearby trees in years to come.

Asparagus grows best in sandy, sandy loam or loam soil that is well draining. Avoid growing asparagus in heavy or clay soil, or in low-lying spots where water does not drain freely, which encourages disease such as fusarium crown rot.

Asparagus is best grown outdoors in the ground, unraised/ground level gardens if the soil is suitable. Since asparagus is a perennial, raised beds higher than 15 cm may not provide enough winter protection for the root system.

Asparagus is not suited to outdoor or indoor containers, hydroponic, straw bale, or other alternative growing methods.


Asparagus transplants and crowns should be planted out in spring or early summer, as soon as the ground has thawed and soil can be easily worked.

If growing asparagus from seed, start seeds in February for planting out as transplants in spring.

The timing of planting should coincide with your frost-free dates. We've given suggested dates below, but you can adjust these to your local conditions. 

  • Knowing the last expected spring frost date for your location will help you plan when to sow seeds. The date is based on averages and varies according to where you live – it is as early as mid-May for Saskatoon, Estevan and Swift Current, SK, while Yellowknife is May 30 and the Moosonee region in Manitoba is June 10. Find the date of the last spring frost at this link: https://climateatlas.ca/map/canada/lastspring_baseline# Click on where you live on the map.

Although seeds can be directly planted out in spring, they need at least one more year of growing compared with transplants to become a productive patch.  It is best to start seedlings indoors in February for planting out in spring.  

Plant seeds 0.5 cm deep in a soil-less mix made of peat or coir, mixed with a small percentage of vermiculite and/or perlite. Choose a 4" pot (or larger) with a hole at the bottom to accommodate and encourage a large root system. 

Asparagus seed is slow to germinate: it can take up to two weeks at room temperature. Asparagus seeds benefit from warmth. Use a heat mat if you have one, or place containers in a warm place like the top of the fridge until they germinate.  Place a clear dome or plastic over the seeded containers to keep moist until germination.

Once seedlings have emerged, place them under grow lights or set them in front of a south-facing window.

Asparagus plants are very tender and fragile when they emerge. To avoid seed rot, do not overwater. Allow the soil to dry out very slightly in between watering. 

Begin fertilizing asparagus seedlings once/week with 20-20-20 water-soluble fertilizer after the seedlings have emerged and are at least 5 cm tall.  Mix the fertilizer according to label directions. 

Seedlings should be hardened off before planting outdoors.

Since asparagus is a perennial crop, it is very important to prepare the soil in the asparagus patch with care and attention.  Choose an area with loam to sandy loam soil.  The soil must have good drainage.  Poorly drained soil will promote Fusarium crown rot disease. 

Before planting, add a layer of well rotted manure (at least 5 cm thick).  Work the manure into the soil and ensure the area is worked well. 

Asparagus transplants and crowns should be planted out in spring or early summer, as soon as the ground has thawed and soil can be easily worked.

Planting instructions for crowns (roots) or transplants

  1. Dig a trench at least 20 cm deep. 
  2. Plant crowns or transplants in the trench 30 cm in the row and allow 2 m between rows. Cover seeds with  and transplants with 5 cm of soil.
  3. After planting crowns or transplants, water in with 10-52-10 fertilizer mixed according to label directions.  This fertilizer is high in phosphorous and will encourage root growth.
  4. As the growing season progresses, fill in the furrow a little with more soil every few weeks. Cover part of the plant but never bury the entire plant.  By the end of the growing season, the trench should be level with the surrounding soil. 

 

Asparagus plants are dioecious:  this means that each plant is either a male or female plant.  Older asparagus cultivars like ‘Martha Washington’ and ‘Viking’ were common cultivars grown on the Prairies in the past.  These cultivars had both male and female plants. 
While both female and male plants produce edible spears, research has shown that female plants may not be as productive as male plants since they also produce fruit (small red berries).  These berries contain seeds which eventually fall off and germinate into new plants.  The formation of these berries (seeds) uses plant resources that are then not be available to produce more or larger spears (the part that we eat!). 
More recently, asparagus cultivars have been released that are male hybrids.  These cultivars are more productive than many of the older named varieties.  Ten years of research at the University of Saskatchewan Vegetable Research Trials have shown that ‘Guelph Millenium’, ‘Guelph Thiessen’, ‘Andreas’, ‘Arianne’, ‘Jersey Supreme’ and ‘Jersey Giant’ consistently outperformed 19 other cultivars, with ‘Guelph Millenium’ being the top yielder every year. 

Other cultivar recommendations:

  1. Here are cultivar recommendations from the North Dakota State University Cultivar Trials, as they share a similar prairie climate and soils. You may download their list here: North Dakota State University Vegetable Cultivar Recommendations for 2021
      •  Jersey Giant, Jersey Knight, Jersey Supreme, Millennium, Purple Passion

While new seedlings need moisture for good growth, it is very important not to overwater your new asparagus patch.  It is best to water less frequently but deeply: about 2.5 cm of water every 7 - 10 days depending on your soil type. Allow at least the top 2.5cm of soil to dry thoroughly before watering.  Wet soil conditions encourage the development of Fusarium crown rot. 

Keep your asparagus patch weed free.  Weed control in perennial crop areas can be a challenge.  Use a shredded arborist woody mulch or seed-free straw mulch between rows to keep weeds down. 

As the season progresses and harvest ends, the asparagus patch turns into a ferny hedge by mid-summer.  Weeding can be a challenge during this time but it is critical to keep weeds to a minimum in this perennial crop.  

Once the asparagus ferns turn yellow and die in the fall, the ferns should be either mowed or removed from the patch in fall.  Gardeners at northern latitudes tend to leave their asparagus ferns in place over winter in order to catch snow to provide extra frost protection to the asparagus crowns.  This is a good practice unless you have noticed asparagus beetles in your patch; most notably, the common asparagus beetle and the spotted asparagus beetle. In that case, mow the ferns to ground level to prevent beetles from overwintering. 

Blanching asparagus

Have you ever wondered how white (blanched) asparagus is grown?  To blanche asparagus mound soil or mulch around the spears in early spring to completely cover them. Another way is to cover crowns with an opaque bucket or box to exclude light.

These mounds exclude the light and limit the amount of chlorophyll that is produced, which results in white spears.  Harvest the blanched spears by digging into the mound. 

Asparagus is not suited to fall seeding.

 

Asparagus can be a challenge in the far north, but it is possible. Asparagus is rated to Zone 2 Plant Hardiness rating.

Asparagus needs a deep layer of soil: 30 - 35 cm or deeper, which can be difficult if you live in an area where soil is thin.

Grow asparagus from crowns instead of seeds. Crowns are available from many on-line seed suppliers. 

An asparagus patch in the far north may benefit from extra winter protection. If you have access to mulch such as straw, lay a thick layer of mulch over the asparagus patch just before the ground freezes. 

If not, bank extra snow over the patch throughout winter to help insulate the soil. 

Here is how Louise Piche grows asparagus in Dawson City, Northwest Territories: 

Fresh northern asparagus

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See our preservation section for more videos.

Growing in containers

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Asparagus is a perennial vegetable and is not suited to container gardening, indoors or out.

Not applicable.

Saving seeds

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Seeds are expected to be shelf-stable for one year from date of sale if purchased from a reputable retailer. If you wish to save your seeds beyond that, you should store them in the fridge in a sealed jar. Seeds lose viability quickly if they dry out too much or get too warm.

The life expectancy of aspagarus seed stored under favourable conditions is about three years.

Seeds stored under less favourable conditions will show poor germination after just a single year of storage. Beyond this, you can expect your germination rates to go down (ie. not all of your seeds will grow, but some might). To test your seeds, you can do a simple germination test. Follow the link for instructions. If you are still getting some seeds germinating, seed more thickly and thin any extra.

Seed saving is not recommended for asparagus. Although asparagus do produce seeds inside round red berries produced by female plants in the fall, there is little control in the quality of plants produced from saved seed. 

If you want to grow asparagus from seed, we recommend purchasing asparagus seeds. 'Guelph Millenium', a top producing asparagus is available as seed from seed catalogues.

Harvest

Do not harvest spear in year 1 and 2: In order to establish a strong, healthy asparagus patch, resist harvesting any spears until your patch is at least 3 years old.  Harvesting prior to year 3 will decrease the vigor of the plot and compromise the health of the developing crowns. 

In year 3, harvest up to 2 spears per plant. 

In year 4, harvest spears for 4-5 weeks. 

In year 5, harvest for 6-8 weeks.  A good rule of thumb is to stop harvesting when spear diameter is less than 10mm (3/8”).  Spears should be harvested when they are 10-20cm (4-10”) in length.  Old spears will be fibrous.  Cut spears up to 5cm below the soil line.

Traditionally, asparagus harvest occurs in spring.  However, in certain parts of Asia, asparagus harvest occurs throughout the growing season.  ‘Mother Stalk’ asparagus harvest refers to a method of harvest in which the first 4-5 spears that emerge in spring are allowed to grow and develop into full sized ferns.  It is these 4-5 ferns that will supply food to the roots throughout the rest of the season.  For the remainder of the season, spears are harvested from this same plant. 

Spears should be harvested when they are 10-20cm (4-10”) in length.  Old spears will be fibrous.  Cut spears with a sharp knife up to 5cm below the soil line.

Storage

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Asparagus has a surprising high respiration rate and must be cooled immediately after harvesting to prevent spears from becoming tough, flavour loss and to prevent soft decay. 

Ideal storage conditions for asparagus is near 0˚C with high humidity (95%). Your fridge is likely a few degrees warmer than this, but that's fine. 

To maintain adequate but not excessive humidity either poke a few holes in your bag (ok), or use a plastic bag meant for vegetables (better), or keep a few sheets of paper towel in the bag with them and switch the paper towels for new ones once they become too moist (best). Asparagus will keep when refrigerated in this way for 1 - 2 weeks.

For longer term storage, we recommend freezing, fermenting, dehydrating (drying) or canning.

Cooking and preserving

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Preservation methods we recommend for asparagus include freezing, fermenting, dehydrating (drying) or canning.

 

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Troubleshooting

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Asparagus are relatively low maintenance once the patch is established. Providing their water, light and soil needs are managed they don't tend to get a lot of issues. Ensuring you stay on top of weeding and maintain healthy soil with adequate organic matter will go a long way towards preventing most issues.

Asparagus beetle is the most common pest, and asparagus crown rot the most common disease.

See the Common problems tab on this page for advice on other specific asparagus issues.

 

 

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Research

These new hybrids are not available yet to home gardeners, but we will update as new information becomes available:

New hybrid asparagus from the University of Guelph

Also - work on fusarium crown rot:

Pathogens in asparagus research Michigan State University 

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