When To Plant Asparagus In Illinois

If you’re planning a perennial vegetable garden in Illinois, knowing when to plant asparagus is the most important first step. Getting the timing right gives your new crowns the best chance to establish strong roots for a harvest that can last for decades.

This guide will walk you through the ideal planting window, variety selection, and step-by-step bed preparation. With a little patience upfront, you’ll be rewarded with delicious, homegrown spears every spring.

The best time for planting asparagus in Illinois is in early spring, as soon as the soil is workable. This typically falls between late March and mid-April for most of the state. The goal is to get the crowns in the ground when they are still dormant, before new growth begins.

Planting too early in cold, wet soil can cause the crowns to rot. Planting to late, when the crowns have already started sprouting, can stress the plant. Watch for the soil to dry out enough that it doesn’t clump when you squeeze it—that’s your signal.

Why Spring Planting is Essential

Spring planting allows the asparagus plant to focus all its energy on developing a massive root system. This underground network, called the crown, stores energy for the winter and fuels spear production the following year. A strong first season sets the stage for future harvests.

Fall planting is generally not recommended in Illinois. Our winters can be to harsh, with freezing and thawing cycles that can heave newly planted crowns right out of the ground.

Choosing the Right Asparagus Variety

Selecting a variety suited to our climate is key. Look for rust-resistant and cold-hardy types. Here are some excellent choices for Illinois gardens:

Jersey Series (Jersey Knight, Jersey Giant, Jersey Supreme): All-male hybrids that produce larger yields because they don’t waste energy on seeds. They are very winter-hardy.
Purple Passion: Offers beautiful purple spears that turn green when cooked. It’s sweeter and more tender than many green types.
Mary Washington: A reliable, old-fashioned heirloom variety that is well-adapted and disease-resistant.

Preparing Your Asparagus Bed

Asparagus will grow in the same spot for 15 years or more, so proper bed preparation is a non-negotiable investment. Follow these steps for success.

Step 1: Site Selection

Choose a location with full sun—at least 8 hours of direct light per day. The site must have excellent drainage; asparagus roots will not tolerate soggy conditions. Avoid areas where water tends to pool after a rain.

Step 2: Soil Testing and Amendment

Asparagus thrives in neutral to slightly alkaline soil (pH 6.5-7.5). It’s a great idea to get a soil test from your local extension office. Amend the soil based on the results.

For heavy clay soil (common in Illinois), add generous amounts of compost and well-rotted manure to improve drainage and fertility.
Incorporate a balanced, slow-release organic fertilizer into the top 12 inches of soil.

Step 3: Digging the Trench

This is the classic method for planting crowns.

Dig a trench that is 12 inches wide and 8-10 inches deep. The length depends on how many plants you have (space crowns 18 inches apart).
Create a 4-inch high mound of soil down the center of the trench.
Place the asparagus crowns on top of the mound, letting the roots drape down the sides like an octopus.
Space crowns 18 inches apart in the trench, with rows 4-5 feet apart.

The Planting Process

Gently place each crown on the soil mound, taking care not to break the roots.
Cover the crowns initially with just 2-3 inches of the excavated soil.
Water the trench thoroughly to settle the soil and remove air pockets.
As the spears begin to grow through the soil, gradually fill in the trench with more soil over the course of the summer. By the end of the season, the trench should be level with the surrounding ground.

Caring for Your New Asparagus Plants

First-year care is all about encouraging strong roots, not harvesting spears.

Watering: Provide 1-2 inches of water per week, especially during dry spells. Consistent moisture is crucial for establishment.
Weeding: Weed carefully by hand, as asparagus roots are shallow and easily damaged by tools. Applying a thick layer of mulch (straw or shredded leaves) after filling the trench will supress weeds and retain moisture.
No Harvesting: Resist the temptation to harvest any spears in the first year. Let them grow into tall, ferny foliage. This photosynthesis feeds the crown.

The Patience Payoff: Harvesting Timeline

Asparagus requires patience, but the schedule is straightforward:

Year 1: No harvest. Let all spears grow into ferns.
Year 2: You can harvest lightly for 2-3 weeks in spring. Stop when spears become thinner than a pencil.
Year 3 and Beyond: Enjoy a full harvest season of 6-8 weeks. Stop harvesting by early July to allow the plants to store energy for next year.

Seasonal Maintenance for Established Beds

Once established, your asparagus bed needs minimal but specific care.

Spring: Apply a balanced fertilizer or a top-dressing of compost before spears emerge. Remove any winter mulch to allow the soil to warm.
Summer: After harvest ends, let the ferns grow. They provide all the nutrients for next year’s crop. Keep the bed weeded and watered during droughts.
Fall: After the first hard frost turns the ferns brown, cut them down to about 2 inches above the ground. Remove and destroy the foliage (don’t compost) to help control pests like asparagus beetles.
Winter: Apply a light layer of straw or compost after the ground freezes to protect the crowns from temperature swings.

Common Problems and Solutions

Even with good care, a few issues can pop up.

Asparagus Beetles: Hand-pick the black and red beetles and their gray larvae. In severe cases, neem oil can be used.
Rust Disease: Prevent this fungal issue by choosing resistant varieties and ensuring good air circulation around plants.
Poor Yield/Thin Spears: This is often a sign of overharvesting the previous year, under-fertilizing, or the plants simply being to young. Ensure you follow the harvest schedule and fertilize annually.

FAQ: Planting Asparagus in Illinois

Can I plant asparagus from seed instead of crowns?

Yes, but it adds an extra year to the process. Seeds are started indoors in late winter and transplanted outside after danger of frost. You must wait an additional year before any harvest compared to planting crowns.

What is the best month to plant asparagus in northern Illinois?

In northern Illinois (Zones 5a-5b), aim for mid to late April. The soil takes longer to warm up and dry out. Always go by soil condition rather than the calendar.

When should you plant asparagus in central Illinois?

For central Illinois (Zones 5b-6a), the ideal window is usually early to mid-April. Keep an eye on soil moisture to avoid working it when it’s to wet.

Is it to late to plant asparagus in May?

If you find dormant, healthy crowns in May, you can still plant them. Water them well and provide some afternoon shade during their first summer to reduce stress. The harvest timeline will be the same, starting from the planting year.

Can I grow asparagus in a raised bed?

Absolutely. Raised beds offer excellent drainage, which asparagus loves. Just ensure the bed is at least 12 inches deep to accommodate the deep root system. The planting process is the same.

By following this guide and timing your planting for that crucial early spring window, you’ll establish a thriving asparagus patch. The initial work and patience required are well worth it for decades of fresh, homegrown spring harvests.