Asparagus in Zone 6A — Midwest

There's nothing quite like walking out to the garden in spring and snapping off fresh asparagus spears for dinner. The flavor is a world away from what you find at the store. Here in the Midwest, our fertile soil and good summer heat give the plants all the energy they need to produce for years, making it one of the most rewarding long-term investments you can make in your garden.

Asparagus is a perennial, which means it’s built to handle our cold winters and come back stronger each year. While our variable spring weather can be a headache for some plants, established asparagus just shrugs it off. You just need to get the timing right for planting, and then it's mostly a game of patience for the first couple of years.

You’ll want to plant one-year-old asparagus crowns, which are dormant root systems. Starting from seed is possible, but it adds at least another year to the long wait for your first harvest. The best time to get these crowns in the ground here is in mid to late April, once the soil is workable and the threat of a hard freeze has passed.

Dig a trench about 6 inches deep and place the crowns with their roots spread out, spacing them about 18 to 24 inches apart. Cover them with just a couple of inches of soil mixed with compost. As the spears grow, you'll gradually fill the trench in over the season. Even in late April, always keep an eye on the forecast for a late frost; a light blanket can protect the first tender shoots if needed.

For the first year, your main job is to help the crowns get established. Water them consistently, giving them about an inch of water a week if we don't get any rain. This helps them develop the deep root system they need to thrive.

Once your asparagus bed is a couple of years old, it becomes remarkably self-sufficient. Our typical Midwest summers provide enough rainfall to keep them happy most of the time. Those deep roots make them quite drought-tolerant, so you’ll likely only need to water during those extended summer heat spells when we go a week or two without a good storm.

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 them a deep soaking at the base of the plants. Avoid overhead watering, as our humid summers can encourage fungal diseases on the ferns. A good layer of straw mulch will help hold in moisture during dry spells and keep the soil from getting baked into a brick, which our clay soil loves to do.

The most important rule with asparagus is to let the ferns grow. After you finish harvesting in late spring, the spears that shoot up will open into tall, airy ferns. These are the plant's solar panels, gathering sunlight and sending energy down to the crown for next year's crop. Do not cut these down during the summer.

Your only pruning job comes after our first hard frost in mid-October turns the ferns yellow or brown. You have two options: you can cut the dead ferns down to the ground in late fall to tidy up the bed, or you can leave them standing through our cold winters to help trap snow for insulation and moisture. If you leave them, just be sure to clear them away in early spring before the new spears start to emerge.

Patience is the name of the game. You should not harvest anything the first year you plant, and only a very light harvest in the second year. The real harvest begins in the third spring, usually starting around mid-April here in Zone 6A.

Look for spears that are 6 to 8 inches tall and at least as thick as a pencil. The tips should be tight and compact. To harvest, you can either snap the spear off at the soil line with your hands or cut it just below the surface with a clean knife. Be careful not to injure the crown or other emerging spears.

Check your patch every day or two, as the spears can grow quickly in warm spring weather. Harvest all the spears that are ready for about 6 to 8 weeks. Once the new spears start emerging thin (pencil-width or less), stop harvesting immediately. This is the plant's signal that its energy reserves are running low. Let these thin spears grow into ferns to power the plant for the next season.

• What it looks like: Small, dark beetles with cream-colored spots crawling on the ferns. You might also see their dark eggs laid in neat rows on the spears or damage like chewing and browning on the tips.
• What causes it: A common pest that overwinters in garden debris. They emerge in spring ready to feed on the new growth.
• How to fix/prevent it: The easiest method is to hand-pick them off in the morning and drop them into a bucket of soapy water. In the fall, be sure to clean up the dead fern debris thoroughly to eliminate their winter hiding spots.

• What it looks like: The ferns will look weak, yellow, and stunted. In advanced cases, the base of the plant may be mushy, and the whole plant can wilt and die.
• What causes it: This is a big one for us, thanks to our heavy clay soil and wet springs. The soil holds too much water, and the crowns essentially drown and rot.
• How to fix/prevent it: Prevention is key. Before you even plant, amend your soil heavily with compost to improve drainage. Planting in a raised bed is an excellent solution if you have particularly dense clay. Be careful not to overwater, especially after the first year.

• What it looks like: The spears emerging from the ground are consistently skinny, about the width of a pencil or less.
• What causes it: The most common cause is over-harvesting—either harvesting for too many weeks in a season or harvesting too heavily in the plant's first couple of years. It can also be a sign of low soil fertility.
• How to fix/prevent it: Be disciplined. Do not harvest in year one. Harvest lightly in year two. In year three and beyond, stop harvesting after about 8 weeks, or as soon as you see the spears thinning out. Top-dressing the bed with a fresh layer of compost each spring will also help keep the plants fed and vigorous.

Here in the Midwest, our biggest challenge with asparagus is drainage. Our fertile but often heavy clay soil, combined with wet spring weather, creates a perfect storm for crown rot. Amending your soil or using raised beds isn't just a suggestion; it's the best way to ensure your patch survives for the long haul. Our adequate summer rainfall is a benefit, meaning less work for you, but it also means you must be vigilant against overwatering.

Good companion planting can help your asparagus patch thrive. Tomatoes are a classic partner because they release a compound from their roots that can help deter the asparagus beetle. Since we plant our tomatoes out around Memorial Day, after the asparagus harvest is winding down, they make great neighbors for the summer. Herbs like parsley and basil are also good to plant nearby, as their strong scents can help confuse and repel pests.

On the other hand, you should avoid planting anything from the allium family—like garlic, onions, and leeks—near your asparagus. They compete for the same specific nutrients in the soil and can release substances that inhibit the growth of the asparagus crowns. It's best to give them their own separate bed.