Asparagus in Zone 5A — Midwest

Asparagus is a Midwest garden staple. The taste of freshly harvested spears, grilled or roasted, is far superior to anything you'll find at the grocery store. Plus, asparagus is a perennial, so once you get it established, you'll have a reliable harvest for years to come.

We know Midwest weather can be unpredictable. The key with asparagus is patience and proper timing. Our growing season is about 157 days, which gives you plenty of time to get your asparagus established and enjoy a harvest.

Transplant your asparagus crowns outdoors around early May. This is when the risk of frost has passed, but the soil is still cool enough for the crowns to establish themselves. Before planting, harden off your asparagus crowns by gradually exposing them to outdoor conditions for about a week.

When transplanting, space the crowns 18-24 inches apart in rows. Remember that you're buying 1-year-old crowns to start. Growing from seed in our climate takes too long – you won't see a harvest for three years or more.

Established asparagus is fairly drought-tolerant, but proper watering is still important, especially in the first two years. During the spring, when new growth is emerging, give your asparagus about 1 inch of water per week, either from rainfall or irrigation. Use the finger test – if the top 2 inches of soil are dry, it's time to water.

During our moderate-to-hot Midwest summers, increase watering to 1.5 inches per week, especially during any heat spells. Water at the base of the plants to avoid getting the foliage wet, which can promote fungal diseases in our moderate-to-humid climate.

Signs of underwatering include wilting or yellowing spears. Overwatering, on the other hand, can lead to crown rot, so make sure your soil is well-draining. A layer of mulch can help retain moisture and regulate soil temperature.

Asparagus requires minimal pruning. The most important thing is to let the ferns grow all summer and fall. These ferns photosynthesize and feed the crown, ensuring a good harvest next year.

In late fall or early spring, after the ferns have died back and turned brown from the first frost around early October, you can cut them down to the ground. Make sure you don't harvest spears for more than 8 weeks each season – you need to let them fern out to keep the plant healthy.

You can expect your first small harvest of asparagus in late April through mid October, about two years after transplanting the crowns. 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. Avoid cutting them, as this can damage the crown. Continue harvesting spears until they start to become thin, about the width of a pencil. At this point, stop harvesting and let the remaining spears fern out.

As the first frost approaches in early October, stop harvesting completely. The ferns need to remain to help the plant store energy for the winter.

Here are some common problems you might encounter with asparagus in the Midwest:

Asparagus Beetle *What it looks like:* Small, colorful beetles (metallic blue or black with orange markings) and their larvae feeding on spears and ferns, causing damage and weakening the plant. *What causes it:* These beetles are attracted to asparagus plants. They are more prevalent during warm summer months. *How to fix/prevent it:* Handpick beetles and larvae. Use insecticidal soap or neem oil, especially on young plants. Encourage beneficial insects like ladybugs.

Crown Rot *What it looks like:* Yellowing and wilting ferns, stunted growth, and eventually, the crown rots and dies. *What causes it:* Poorly drained soil and fungal diseases. Our wet-summer rainfall can exacerbate this, especially in clay soil. *How to fix/prevent it:* Ensure good drainage when planting. Amend heavy clay soil with compost. Avoid overwatering. Remove and destroy infected plants.

Thin Spears *What it looks like:* Spears that are very thin, even early in the harvest season. *What causes it:* Over-harvesting the previous year, not allowing the plants to fern out and store energy. *How to fix/prevent it:* Limit your harvest to 6-8 weeks each season. Allow the plants to fern out and replenish their energy reserves. Fertilize in early spring.

Midwest Specific Challenges: Our moderate-to-humid climate can promote fungal diseases like crown rot, so good drainage and proper watering are essential. Also, our summer heat spells can stress asparagus plants, making them more susceptible to pests and diseases. Make sure to water deeply during these periods.

Companion planting can help your asparagus thrive. Tomatoes, parsley, and basil are good companions. Tomatoes deter asparagus beetles. Parsley attracts beneficial insects. Basil also repels asparagus beetles and other pests.

Avoid planting asparagus near onions or garlic. These plants can inhibit asparagus growth. They release compounds into the soil that can stunt the growth of asparagus.