Asparagus in Zone 6B — Midwest

There's nothing quite like heading out to the garden in the spring and cutting fresh asparagus for dinner. The flavor is worlds away from what you find in the store, and growing it yourself is one of the most satisfying things you can do. Here in the Midwest, our fertile soil and good summer heat give the plants all the energy they need to produce for years to come.

Asparagus is a long-term commitment, but it's perfectly suited for our climate. You'll need to be patient for the first couple of years, but once it's established, it can handle our cold winters and thrive during our 183-day growing season. The key is getting the timing right in our sometimes-unpredictable spring weather.

The best way to start an asparagus patch is with 1-year-old crowns, which are dormant root systems. Growing from seed is possible but adds another year or two of waiting, so it's worth buying the crowns. Your goal is to get them in the ground sometime in mid to late April.

This timing usually avoids the worst of our late frosts, but Midwest weather can always throw a curveball. Before you plant, dig a trench about 6 inches deep and work plenty of compost into the bottom, especially if you have heavy clay soil. Place the crowns in the trench with their roots spread out, spacing them about 18-24 inches apart, and cover them with just a couple of inches of soil. You'll gradually fill the trench in as the spears grow.

For the first year, you'll want to keep your new asparagus patch consistently moist to help the crowns get established. This means about an inch of water a week, either from you or the sky. Our Midwest summers usually provide decent rainfall, so you might not need to water much.

Once your patch is a couple of years old, the deep roots make it quite drought-tolerant. You’ll really only need to water during those summer heat spells when we go a week or two without a good rain. The best way to check is the finger test: stick your finger two inches into the soil. If it's dry, it's time to give the bed a deep, slow soaking.

Always water at the base of the plants. Our moderate-to-humid summers mean that wet foliage can lead to fungal problems. A good layer of straw mulch helps keep the soil moisture even and the weeds down, which is a big help during the busiest part of the season.

The most important part of maintaining your asparagus patch is knowing what *not* to do. After you finish your spring harvest, let all the remaining spears grow up into tall, feathery ferns. Do not cut these down during the summer; they are the plant's solar panels, gathering energy to store in the crowns for next year's crop.

You have two options for the main cleanup. You can wait until late fall, after a few hard frosts have turned the ferns yellow and brown, and then cut them down to the ground. This helps prevent pests like the asparagus beetle from overwintering in the debris.

Alternatively, some gardeners leave the dead ferns in place all winter to help catch snow for insulation and then cut them back in very early spring before any new spears emerge. Either method works well here.

Patience is the name of the game with asparagus. You must let the plant grow for two full seasons without harvesting a single spear. In the third spring, typically starting in mid-April, you can finally take your first light harvest.

Harvest spears when they are about 6 to 8 inches tall and the tips are still tight. The best way is to simply snap them off at the soil line with your hands; they'll break cleanly at the tender point. You can also use a knife, but be careful not to injure the crown or other emerging spears.

In the third year, harvest for only 2-3 weeks. In later years, you can harvest for up to 8 weeks. The signal to stop is when the new spears start coming up thin, about the width of a pencil. Once you see those, stop cutting immediately and let everything fern out to power up for next year.

Even a tough plant like asparagus can run into a few issues in our Midwest gardens. Here are the main ones to watch for.

• What it looks like: You'll see small, dark beetles with cream-colored spots on the ferns. They chew on the spears, causing them to look scarred or bent, and lay dark eggs in rows on the plant.
• What causes it: The beetles overwinter in old asparagus ferns and garden debris, emerging in spring to feed.
• How to fix/prevent it: The easiest method is to hand-pick them off and drop them into soapy water. Cleaning up the dead ferns in the fall is the best prevention, as it removes their winter shelter.

• What it looks like: The ferns will look weak, yellow, and stunted. At the soil line, the base of the plant (the crown) might be mushy and brown.
• What causes it: This is a direct result of poor drainage, a common challenge with our heavy clay soil, especially after a wet spring or summer downpour.
• How to fix/prevent it: Prevention is everything here. Before you even plant, amend your soil heavily with compost to improve its structure. Planting in a slightly raised bed is an excellent strategy to ensure water never sits around the crowns.

• What it looks like: The spears that emerge are consistently as thin as a pencil, or even thinner.
• What causes it: The most common reason is harvesting for too long the previous season, which weakens the plant. It can also mean the crowns are still too young or the soil needs more nutrients.
• How to fix/prevent it: Be disciplined with your harvest window—stop after 8 weeks, or sooner if the spears thin out. Each spring, top-dress the bed with a fresh layer of compost to feed the plants.

Midwest Specific Challenges Our region's heavy clay soil is the biggest factor for asparagus, making crown rot a real possibility if you don't prepare the bed properly. The moderate-to-humid air during our summer heat spells means watering at the base of the plant is important to keep fungal diseases off the ferns. On the bright side, our cold winters provide the perfect dormant period that asparagus needs to thrive year after year.

Putting the right neighbors next to your asparagus can help keep it healthy. Tomatoes are a great partner because they release a substance from their roots that can deter the asparagus beetle. Since you finish harvesting asparagus before it's time to plant tomatoes, they make for a good succession planting in a nearby row. Herbs like parsley and basil are also beneficial, as their strong scents can confuse and repel some pests.

On the other hand, you should keep all members of the onion family—including garlic, shallots, and leeks—away from your asparagus patch. They compete for the same specific nutrients in the soil and can release compounds that inhibit the growth of your asparagus. It's best to give them their own separate bed.