Growing Asparagus in Cold Climates: Planting, Harvest Schedule and Winter Care

Asparagus is a long-term investment that pays off for decades. Once a bed is established, it sends up spears every spring for twenty years or more, and it is hardy to about zone 2. The trick is patience in the first few years and a good start at planting.

The short answer

• Plant crowns in spring in a trench at least 20 cm deep, 30 cm apart, with rows about 2 m apart.
• Choose all-male hybrids such as Guelph Millennium for the biggest yields.
• No harvest for two years. Year 3: up to 2 spears per plant. Year 4: 4 to 5 weeks. Year 5 on: 6 to 8 weeks.
• Let the ferns grow all summer and stand over winter to catch snow.

Based on the University of Saskatchewan asparagus guide.

Choosing a site

• Full to partial sun, away from where trees will shade it in future.
• Sandy, sandy loam or loam soil with good drainage. Avoid heavy clay and wet spots, which cause crown rot.
• Plant at ground level rather than in tall raised beds; USask notes beds raised more than about 15 cm may not protect roots well over winter.
• Work at least 5 cm of well-rotted manure into the bed first.

Best varieties

Female asparagus plants spend energy on red berries instead of spears. All-male hybrids yield more. In ten years of USask trials, Guelph Millennium, Guelph Thiessen, Andreas, Arianne, Jersey Supreme and Jersey Giant beat 19 other varieties, and Guelph Millennium was the top yielder every year. Older varieties like Martha Washington include female plants.

Planting crowns

1. In spring or early summer, once the ground has thawed, dig a trench at least 20 cm deep.
2. Set crowns 30 cm apart along the bottom, with rows about 2 m apart.
3. Cover with about 5 cm of soil and water in with a starter fertilizer.
4. As shoots grow over the next weeks, gradually fill in the trench until it is level with the surrounding soil by the end of the season. Never bury the shoots completely.

Growing from seed is possible but adds at least an extra year. In the far north, USask recommends crowns.

Care

• Water deeply, about 2.5 cm every 7 to 10 days, and let the top few centimetres dry between waterings.
• Keep the bed weed-free, especially early in the season before the ferns fill in.
• Mulch between rows with straw or wood chips.

Harvest schedule

Year	Harvest
1 and 2	None; let the roots establish
3	Up to 2 spears per plant
4	4 to 5 weeks
5 onward	6 to 8 weeks

Cut spears when they are 10 to 20 cm tall, about 5 cm below the soil with a sharp knife. Stop for the season once new spears come up thinner than about 10 mm (pencil thickness).

Fern and winter care

After harvest, let the spears grow into tall ferns. They feed the roots for next year. Let them yellow naturally in fall. If you have asparagus beetles, cut the ferns down in fall so beetles do not overwinter; otherwise leave them standing, since they trap snow that insulates the crowns. In the coldest areas, add a thick layer of straw before the ground freezes.

Keep reading

• Growing rhubarb
• What is my growing zone in Canada?

Frequently Asked Questions

How long before I can harvest asparagus?

Do not harvest for the first two years. In year three, take up to 2 spears per plant; harvest for 4 to 5 weeks in year four and 6 to 8 weeks after that.

What is the best asparagus variety for cold climates?

All-male hybrids yield the most. In University of Saskatchewan trials, Guelph Millennium was the top yielder every year.

How deep do you plant asparagus crowns?

In a trench at least 20 cm deep, covered with about 5 cm of soil at first and filled in gradually as shoots grow.

Should I cut down asparagus ferns in fall?

Only if you have asparagus beetles. Otherwise leave them standing over winter to trap insulating snow.

Sources

• University of Saskatchewan Gardenline – Asparagus