Asparagus in Zone 5A — Great Plains

Asparagus is a worthwhile investment for any Great Plains gardener. The unique flavor of fresh asparagus, snapped right from your garden, beats anything you can find at the store. Plus, asparagus is incredibly versatile in the kitchen, and there's a special satisfaction in harvesting your own food year after year from a perennial crop.

Our region's extreme weather can seem daunting, but asparagus is surprisingly resilient. With a little planning and attention to timing, you can successfully grow asparagus even with our 168-day growing season and variable rainfall.

Transplant your asparagus crowns outdoors from late April through early May, after the last expected frost. Before planting, harden off your crowns by gradually exposing them to outdoor conditions for about a week. This helps them adjust to our fluctuating Plains temperatures.

Space the crowns 18-24 inches apart in well-drained soil. Keep an eye on the forecast; those late-season cold snaps can still happen, so be ready to cover your young plants if necessary. Remember to buy 1-year-old crowns, as growing from seed can take several years before you get your first harvest.

Established asparagus is fairly drought-tolerant, thanks to its deep roots, but consistent watering is crucial, especially during the first two years. In our Plains climate, where summers are hot and rainfall is variable, a good rule of thumb is to water deeply about once a week, providing about 1 inch of water. Adjust this based on rainfall and soil conditions.

Before watering, do the finger test: stick your finger about 2 inches deep into the soil near the base of the plant. If it feels dry, it's time to water. Because we tend to have low-to-moderate humidity, watering at the base of the plant is generally preferable to overhead watering, which can encourage fungal diseases in some situations.

Signs of underwatering include wilting or yellowing spears. Overwatering can lead to crown rot, which is especially a risk in poorly drained soils. A good layer of mulch, like straw or wood chips, will help retain moisture and regulate soil temperature, which is especially helpful with our extreme temperature swings.

Asparagus requires minimal pruning. The most important thing is to let the ferns grow and mature all summer. These ferns are essential for feeding the crown and ensuring a good harvest in future years.

In late fall or early spring, after the ferns have died back and turned brown, you can cut them back to ground level. Don't harvest for more than 8 weeks per season to avoid weakening the plant.

You can expect your first harvest of asparagus spears in late April through late October, about two years after transplanting. Look for spears that are 6-8 inches tall with tight, closed tips. These are the most tender and flavorful.

To harvest, snap the spears off at ground level. Be careful not to damage the surrounding spears or the crown. Continue harvesting regularly as the spears emerge. As the season progresses, you'll notice the spears becoming thinner, sometimes down to pencil-width. This is a sign to stop harvesting and allow the remaining spears to fern out, which will replenish the plant's energy reserves for the following year.

As our first frost approaches in early October, it's time to let all remaining spears fern out, even if they are still thick. This ensures the plant has enough stored energy to survive the winter and produce a good crop next spring.

Here are some common problems you might encounter growing asparagus in the Great Plains:

Asparagus Beetle

• What it looks like: Small, elongated beetles (often orange or black with markings) and their larvae feeding on spears and ferns, causing damage and discoloration.
• What causes it: Beetles are attracted to asparagus plants and can quickly multiply, especially in neglected gardens.
• How to fix/prevent it: Handpick beetles and larvae. Encourage beneficial insects like ladybugs. Use insecticidal soap as a last resort, following label instructions carefully.

Crown Rot from Poor Drainage

• What it looks like: Yellowing or wilting spears, stunted growth, and a mushy, decaying crown.
• What causes it: Soggy soil and poor drainage create an environment where fungal pathogens thrive, attacking the crown. This is exacerbated by our variable rainfall.
• How to fix/prevent it: Plant asparagus in well-drained soil. Amend heavy clay soil with compost and other organic matter. Avoid overwatering. Ensure proper drainage in the planting bed.

Thin Spears from Over-Harvesting

• What it looks like: Spears that are noticeably thinner than usual, sometimes pencil-thin, even early in the harvest season.
• What causes it: Harvesting too many spears for too long depletes the plant's energy reserves, leading to weaker growth.
• How to fix/prevent it: Limit your harvest to 6-8 weeks per season. Allow plenty of spears to fern out and replenish the crown's energy. Ensure adequate watering and fertilization.

Great Plains Specific Challenges: Our hot summers and variable rainfall can stress asparagus plants, making them more susceptible to pests and diseases. Be vigilant about watering during dry spells, but avoid overwatering, especially in heavy soils. The wind can also damage the ferns, so consider providing some wind protection, especially for young plants.

Good companions for asparagus in the Great Plains include tomatoes, parsley, and basil. Tomatoes deter asparagus beetles, while parsley attracts beneficial insects that prey on asparagus pests. Basil also repels asparagus beetles and improves the overall health of the asparagus plants.

Avoid planting asparagus near onions and garlic. These plants can inhibit asparagus growth, potentially stunting their development in our already short growing season.