Knowing the right time to get your asparagus crowns in the ground is the first step to a successful harvest. This guide will explain exactly when to plant asparagus in Wisconsin and provide a full season plan.
Asparagus is a unique perennial vegetable that, with proper care, can produce for 15 years or more. Getting the planting timing and method right from the start is crucial, as you won’t harvest your first spears for a few seasons. Let’s get your Wisconsin asparagus patch off to a strong start.
When to Plant Asparagus in Wisconsin
The ideal planting window for asparagus in Wisconsin is in early spring, as soon as the soil is workable. This typically falls between mid-April and early May. The key signal is soil temperature.
You should plant when the soil has warmed to about 50°F (10°C). Planting into cold, soggy soil can cause the crowns to rot. A good rule of thumb is to plant asparagus around the same time you plant your earliest peas or potatoes.
Here’s a quick reference for Wisconsin’s zones:
* Southern Wisconsin (Zones 5b): Aim for mid to late April.
* Central/Northern Wisconsin (Zones 4a-5a): Aim for late April to early May.
Always let soil conditions be your final guide. If spring is late and the ground is still frozen or waterlogged, wait a little longer.
Why Spring Planting is Essential
Planting in spring gives the asparagus crowns a full season to establish their extensive root system before winter. This strong foundation is what fuels vigorous spear production in the coming years. Fall planting is generally not recommended in Wisconsin, as young crowns are vulnerable to harsh winter freeze-thaw cycles.
Choosing the Right Asparagus Variety
Selecting a variety suited to your garden and climate will improve your success. Most are hybrids of Asparagus officinalis. Consider these popular and reliable choices:
* Jersey Series (Jersey Knight, Jersey Supreme, Jersey Giant): These all-male hybrids are highly recommended for Wisconsin. They produce more spears because they don’t waste energy on seed production. They are also known for their disease resistance and cold hardiness.
* Purple Passion: This variety offers beautiful, sweet, purple spears. It turns green when cooked. It’s a bit more tender and is grown from seed more often, which adds a year to establishment.
* Mary Washington: A traditional, reliable heirloom variety. It is less expensive but produces both male and female plants, leading to slightly lower yields and potential self-seeding.
For most gardeners, a Jersey variety is the best bet for a productive, low-maintenance bed.
Site Selection and Soil Preparation
Asparagus will live in the same spot for decades, so choosing and preparing the site is the most important step. Don’t rush this part.
Sun and Space:
Asparagus needs full sun—at least 8 hours of direct sunlight daily. Choose a location at the edge of your garden where the tall, ferny foliage won’t shade other plants. Each crown needs space, so plan for a bed that is at least 4 feet wide and as long as you desire.
Soil Requirements:
Asparagus thrives in well-drained, fertile soil. Heavy clay or sandy soil needs amendment.
* Drainage is Critical: Roots will rot in standing water. If you have heavy soil, consider building a raised bed.
* pH Level: Aim for a slightly alkaline soil pH between 6.5 and 7.5. A simple soil test from your county extension office can tell you your pH.
* Weed Control: Start with a completely weed-free area. Perennial weeds like quackgrass are very difficult to remove once asparagus is planted.
How to Prepare the Bed:
1. The previous fall is the best time to start. Clear all weeds and grass.
2. Dig a trench 12-18 inches wide and 8-10 inches deep.
3. Mix the excavated soil with generous amounts of compost and well-rotted manure. Adding a balanced, slow-release fertilizer at this stage is also beneficial.
4. Fill the trench back in with this enriched mixture, creating a mounded row. This will settle over winter and be ready for spring planting.
Step-by-Step Planting Guide
Once your soil is ready and the timing is right, follow these steps.
What You’ll Need:
* Healthy, one-year-old asparagus crowns
* Compost
* Balanced organic fertilizer
* Garden hose or watering can
* Mulch (straw or shredded leaves)
Planting Steps:
1. Soak the Crowns: Before planting, soak the bare-root crowns in lukewarm water for 15-20 minutes.
2. Dig Trenches: In your prepared bed, dig trenches 6-8 inches deep and about 12 inches wide. Space trenches 3-4 feet apart if you have more than one.
3. Create Mounds: Form a small ridge of soil down the center of the trench, about 2-3 inches high.
4. Place the Crowns: Set the crowns on top of the ridge, spreading the roots out evenly like an octopus. Space crowns 12-18 inches apart within the row.
5. Cover Gently: Cover the crowns with 2-3 inches of the loosened, amended soil. Do not fill the trench completely yet.
6. Water Thoroughly: Give the newly planted crowns a good, deep watering.
7. Fill Gradually: As the shoots begin to grow through the soil, gradually add more soil to the trench every few weeks until it is level with the surrounding ground.
Caring for Your New Asparagus Bed
The first two years are about building plant strength, not harvesting.
* Watering: Provide 1-2 inches of water per week during the first growing season. Consistent moisture is key for establishment.
* Weeding: Weed carefully by hand, as asparagus roots are shallow and easily damaged. Mulching with straw helps tremendously with weed suppression and moisture retention.
* Feeding: In early summer, side-dress the plants with compost or a balanced fertilizer. A second feeding in late summer after growth has slowed can also be helpful.
The Patience Payoff: Harvesting Timeline
Resisting the urge to harvest early ensures a long-lived bed.
* Year 1: Do not harvest. Let all the spears grow into tall, ferny foliage. This photosynthesis builds the crown’s energy reserves.
* Year 2: You may harvest lightly for 2-3 weeks in spring if the spears are robust (pencil-thick or larger). If plants seem weak, wait another year.
* Year 3 and Beyond: You can harvest for a full season of 6-8 weeks. Stop harvesting when spear diameter becomes noticeably thinner, usually around early July.
Seasonal Maintenance for Established Beds
Once established, your asparagus bed requires simple seasonal care.
* Spring: Remove and destroy the previous year’s dead, brown fern growth before new spears emerge to discourage pests. Begin your harvest when spears are 6-8 inches tall.
* Summer: After harvest ends, let the ferns grow. They are beautiful and vital. Keep the bed weeded and watered during dry spells.
* Fall: After a hard frost turns the ferns yellow/brown, you can cut them down to 2-inch stubs. Apply a fresh layer of compost or well-rotted manure as a winter mulch and nutrient boost.
Common Problems and Solutions in Wisconsin
Even with good care, a few issues can pop up.
* Asparagus Beetles: These black and red beetles chew on spears and ferns. Hand-pick them off or use an organic spray like neem oil if infestation is severe.
* Rust (Fungal Disease): Shows as orange pustules on ferns. Ensure good air circulation, choose resistant varieties (like Jersey types), and remove infected fern debris in fall.
* Poor Yield: Thin spears often indicate underfeeding, overcrowding, or too-early harvesting. Ensure proper fertility and follow the harvest schedule.
* Winter Damage: In very cold areas, a late-fall mulch of straw after the ground freezes can protect crowns from heaving.
FAQ: Wisconsin Asparagus Planting Guide
Q: Can I grow asparagus from seed in Wisconsin?
A: Yes, but it adds at least one extra year to the establishment process. Start seeds indoors in late winter and transplant seedlings in summer. Most gardeners prefer the faster start with one-year-old crowns.
Q: How many asparagus plants should I plant per person?
A: A good rule is 10-15 crowns per person for fresh eating. A family of four might start with 30-40 crowns for a plentiful harvest.
Q: What should I not plant near asparagus?
A: Avoid planting asparagus near onions, garlic, or potatoes, as they can compete for resources. Good companions include tomatoes, parsley, and basil, which may help deter asparagus beetles.
Q: My asparagus spears are very thin. What’s wrong?
A: Thin spears are normal in the first harvestable year. In established beds, it usually means the harvest period was to long the previous year, the plants need more fertilizer, or the bed is overcrowded.
Q: When is it to late to plant asparagus in spring?
A: It’s best to plant by late May. Planting in early summer exposes young crowns to heat stress before they are established. If you miss the window, it’s better to wait until the following spring and order your crowns early.
Starting an asparagus bed is an investment in your garden’s future. By planting at the right time, preparing the soil deeply, and practicing patience during the first few years, you’ll be rewarded with a delicious, perennial harvest every spring for many years to come.