Asparagus in Zone 3B — Great Plains

Asparagus is a worthwhile perennial for any Great Plains garden. The taste of freshly harvested spears is far superior to anything you'll find in a store. Plus, asparagus is a reliable producer once established, offering years of delicious harvests and beautiful, feathery foliage.

Our region certainly has its challenges, from temperature swings to variable rainfall. But with careful timing and a little extra attention during those first few years, you can enjoy a thriving asparagus patch. The 118-day growing season might seem short, but asparagus is surprisingly hardy and adapts well here.

Plan to transplant your asparagus crowns outdoors in mid- to late May, once the risk of a hard frost has passed. Before planting, be sure to harden off your crowns. Gradually expose them to outdoor conditions for about a week, starting with just a few hours a day.

Space the crowns 18-24 inches apart in well-draining soil. Even in late May, we can still get some unexpected cold snaps, so keep an eye on the forecast and be prepared to cover your young plants if necessary. Buying 1-year-old crowns is the best way to go, as starting from seed can take 3+ years before you get your first harvest.

Asparagus needs moderate watering, especially during its first two years as it establishes. Once established, its deep roots make it fairly drought-tolerant, which is a definite plus in our variable Plains climate. Keep in mind that even drought-tolerant plants benefit from consistent moisture during hot, dry stretches.

During the heat of summer, give your asparagus patch a good soaking if we haven't had rain for a week or so. Stick your finger about 2 inches into the soil near the plants. If it feels dry, it's time to water. Aim for about 1 inch of water per week, delivered at the base of the plants to avoid fungal issues in our moderate humidity.

Signs of underwatering include wilting or yellowing foliage, while overwatering can lead to root rot. A layer of mulch, like straw or wood chips, will help retain moisture and regulate soil temperature, which is particularly beneficial during our extreme temperature swings.

Asparagus pruning is pretty minimal. The key is to let the ferns grow and thrive all summer long. These ferns are essential for feeding the crown and ensuring a good harvest next year.

Once the ferns have died back in late fall or early spring, you can cut them back to ground level. Just be sure to do this before new spears start to emerge. Avoid harvesting for more than 8 weeks each season to allow the plants to recharge.

You can expect your first harvest of asparagus spears starting in mid-May through late September, about two years after transplanting the crowns. Look for spears that are 6-8 inches tall with tight, unopened tips.

To harvest, simply snap the spear off at ground level. Avoid cutting, as this can damage the crown. Continue harvesting spears until they start to thin out to about the diameter of a pencil. At that point, stop harvesting and let the remaining spears fern out to build up energy for the following year.

As our first frost approaches around mid-September, it's time to wrap up the harvest and let the plants focus on storing energy for the winter. Even if there are still some spears emerging, it's best to leave them be.

Asparagus can have a few problems in our region. Here are three common ones:

Asparagus Beetle

• What it looks like: Small, metallic blue or black beetles and their larvae feeding on spears and ferns. You might also see small, dark eggs laid in rows on the spears.
• What causes it: These beetles are attracted to asparagus plants, especially during warm weather. Our warm summers provide ideal conditions for them to thrive.
• How to fix/prevent it: Handpick beetles and larvae when you see them. Introduce beneficial insects like ladybugs, or use insecticidal soap as a last resort.

Crown Rot

• What it looks like: Yellowing or wilting foliage, stunted growth, and mushy, brown roots.
• What causes it: Poor drainage and overly wet soil lead to fungal diseases that cause the crown to rot. Heavy spring rains, coupled with poorly draining soil, can exacerbate this problem.
• How to fix/prevent it: Plant asparagus in well-draining soil. Avoid overwatering, and amend heavy clay soils with compost or other organic matter.

Thin Spears

• What it looks like: Spears that are significantly thinner than usual, sometimes even pencil-thin.
• What causes it: Over-harvesting, which weakens the plant and depletes its energy reserves.
• How to fix/prevent it: Limit your harvest to 6-8 weeks per season. Allow plenty of ferns to grow after the harvest period to replenish the plant's energy.

Great Plains Specific Challenges: Our hot summers and variable rainfall can stress asparagus plants. Drought can weaken them, making them more susceptible to pests and diseases. The extreme temperature swings can also impact growth. Consistent watering during dry periods and a good layer of mulch can help mitigate these challenges.

Good companion plants for asparagus include tomatoes, parsley, and basil. Tomatoes provide shade and support for asparagus ferns, while parsley attracts beneficial insects that prey on asparagus beetles. Basil can help repel asparagus beetles with its strong scent.

Avoid planting asparagus near onions and garlic. These plants are allelopathic to asparagus, meaning they release substances that can inhibit its growth. Keeping these plants separate will help your asparagus thrive in our Plains garden.