How to Successfully Grow Asparagus in Minnesota

Growing asparagus in Minnesota can be a rewarding experience for gardeners willing to invest time and patience. Asparagus (Asparagus officinalis) is a perennial vegetable that, once established, can produce fresh, delicious spears for 15 years or more. However, Minnesota’s cold climate and relatively short growing season mean that special care and preparation are necessary to grow asparagus successfully. This comprehensive guide will walk you through the essential steps to ensure your asparagus thrives in the Land of 10,000 Lakes.

Understanding Asparagus and Its Growth Cycle

Before diving into the specifics of growing asparagus in Minnesota, it’s important to understand the nature of this vegetable:

• Perennial Crop: Asparagus crowns (roots) are planted once and can produce for many years.
• Slow Start: The first few years require patience as you allow the plants to establish.
• Cold Tolerance: Asparagus is hardy and can survive harsh winters if properly prepared.
• Harvesting: Typically begins 2-3 years after planting crowns, once plants are mature.

Choosing the Right Variety for Minnesota

Selecting an asparagus variety suited to Minnesota’s climate is crucial. Look for cold-hardy varieties with good disease resistance.

Recommended Varieties:

• Jersey Knight: Cold hardy, disease-resistant, and produces thick spears.
• Jersey Giant: Known for vigor and good spear quality.
• Mary Washington: Traditional variety, well-adapted but slightly less disease resistant.
• Purple Passion: Unique purple spears with good cold tolerance.

Site Selection: Where to Plant Asparagus in Minnesota

The success of your asparagus crop largely depends on choosing the right location.

Sunlight:

• Full sun exposure (at least 6-8 hours daily) is essential for healthy spear production.

Soil:

• Well-drained soil is vital; asparagus roots will rot in waterlogged conditions.
• Sandy loam or loamy soil with good organic matter content works best.
• Avoid low spots prone to standing water during spring thaw.

pH Level:

• Aim for a slightly acidic to neutral soil pH between 6.5 and 7.0.

Space:

• Asparagus plants need room to spread. Plan for about 12-18 inches between crowns and rows spaced 3-5 feet apart.

Preparing the Soil

Testing Soil:

Before planting, test your soil’s pH and nutrient levels using a soil test kit or local extension service.

Improving Soil Fertility:

• Add compost or well-rotted manure to enrich the soil.
• Incorporate balanced fertilizer; a general recommendation is 10 pounds of 10-10-10 fertilizer per 100 square feet.

Drainage Improvement:

If your soil tends to retain water, consider building raised beds (12 inches high) to improve drainage and encourage root health.

Planting Asparagus in Minnesota

When to Plant:

Plant asparagus crowns in early spring as soon as the soil can be worked—usually late April to early May in Minnesota, depending on local weather conditions.

Planting Method:

1. Trench Preparation: Dig trenches about 12 inches wide and 8 inches deep.
2. Spacing Crowns: Space crowns 12–18 inches apart within rows.
3. Depth: Place crowns on a small mound of soil or sand at the bottom of the trench with roots spread out.
4. Covering Crowns: Initially cover crowns with 2 inches of soil.
5. Gradual Filling: Over several weeks, gradually fill in the trench as shoots emerge until it is level with surrounding ground.

Watering:

Water immediately after planting and keep soil moist but not soggy through the growing season.

Caring for Asparagus Plants

Water Requirements:

Asparagus needs about 1–2 inches of water per week during its active growth period (spring through early summer). Irrigation may be necessary during dry spells.

Weeding:

Keep beds weed-free as weeds compete for nutrients and water. Mulching can help suppress weeds but avoid heavy mulch that may inhibit spear emergence.

Fertilizing:

Apply fertilizer annually in early spring before new growth begins using a balanced fertilizer or one higher in nitrogen (e.g., 10-20-10).

Mulching:

Apply organic mulch such as straw or shredded leaves around plants after spears have stopped emerging in late spring or early summer. Mulch helps conserve moisture, suppress weeds, and protect roots over winter.

Dealing with Minnesota Winters

Minnesota winters can be harsh, but asparagus is hardy if properly cared for:

• After the last harvest season (usually late June), allow ferns to grow tall to capture sunlight and store energy in roots.
• In fall, once ferns turn brown, cut them down to ground level.
• Apply a thick layer of mulch (6–8 inches) over beds before heavy frosts set in. Straw or chopped leaves work well.

This mulch protects crowns from extreme freeze-thaw cycles that can damage roots.

Harvesting Asparagus in Minnesota

When to Begin Harvesting:

Patience is key — avoid harvesting during the first two growing seasons after planting crowns to allow strong root development.

In year three:
– Begin harvesting when spears reach about 6–8 inches tall.
– Harvest only for about two weeks to avoid stressing plants.

From year four onward:
– Harvest for up to six weeks each spring.

How to Harvest:

Cut or snap spears at ground level when they are thick enough (around pencil diameter).

Avoid harvesting thin or small spears since they indicate immature growth and weak plants.

Stop harvesting when spears become thin (less than pencil size) or begin ferns growing again.

Pest and Disease Management

Minnesota gardeners should monitor asparagus beds regularly for common issues:

Common Pests:

1. Asparagus Beetle:
2. Adults and larvae feed on spears causing scarring and deformities.

3. Control by hand-picking beetles or using insecticidal soaps early in season.

4. Cutworms:

5. Larvae cut young spears at soil level.
6. Use collars around plants and clean garden debris where moths hide.

Common Diseases:

1. Fusarium Wilt:
2. Causes yellowing and wilting of ferns.

3. Use resistant varieties like Jersey Knight; improve crop rotation and avoid planting asparagus continuously in one spot without rest periods.

4. Rust:

5. Orange pustules on foliage reduce vigor.
6. Remove infected plant debris annually; fungicides may be needed if severe.

Extending Your Growing Season

Minnesota’s short growing season can limit asparagus production time, but some techniques help extend it:

• Use black plastic mulch over beds in early spring before spears emerge; it warms soil faster encouraging earlier growth.
• Consider cold frames or row covers during early spring frosts to protect tender shoots.

Troubleshooting Common Issues

| Issue | Cause | Solution |
|——-|——-|———-|
| Sparse spear production | Immature plants or poor site conditions | Wait until year 3+, improve soil fertility |
| Thin or woody spears | Overharvesting or stressed plants | Reduce harvest time, maintain irrigation |
| Spear discoloration | Frost damage or disease | Use frost protection, remove affected parts |
| Poor winter survival | Inadequate mulching | Apply thicker winter mulch |

Conclusion

Growing asparagus in Minnesota requires thoughtful planning, patience, and care due to the state’s challenging climate conditions. By selecting cold-hardy varieties, preparing well-draining fertile soil, planting at the correct time, managing pests thoughtfully, and protecting plants over winter with mulch, gardeners can enjoy delicious homegrown asparagus year after year. Remember that it takes several years before your investment pays off with bountiful harvests—your perseverance will be rewarded with one of spring’s earliest fresh vegetables!

With this guide, you’re ready to start your own successful asparagus patch in Minnesota’s unique environment. Happy gardening!