Pennsylvania gardeners should wait until the soil temperature reaches 50°F for asparagus crowns. Knowing exactly when to plant asparagus in PA can mean the difference between a thriving bed and a disappointing harvest. The timing hinges on your specific region within the state, from the warmer southeast to the cooler northern tier.
Asparagus is a perennial vegetable that can produce for 15 to 20 years once established. Getting the planting window right is your first step toward a long-term, low-maintenance crop. This guide walks you through the exact timing, soil prep, and care steps for Pennsylvania’s unique climate.
When To Plant Asparagus In Pa
The ideal planting window for asparagus crowns in Pennsylvania runs from early April to mid-May. This varies by location. In southeastern PA (Zones 6b-7a), you can start as early as late March if the ground is workable. In central PA (Zones 6a-6b), aim for mid-April. In northern PA and the Poconos (Zones 5a-5b), wait until early to mid-May.
The key indicator is soil temperature, not the calendar. Use a soil thermometer to check at 4 inches deep. When it hits 50°F consistently, you’re good to go. Planting too early in cold, wet soil can cause crown rot. Planting too late reduces the first-year root development.
Understanding Pennsylvania’s Growing Zones
Pennsylvania spans USDA hardiness zones 5a to 7b. This means your planting date shifts by about two weeks for each zone change. Here’s a quick breakdown:
- Zone 5a-5b (Northern PA, high elevations): Plant mid-May to late May
- Zone 6a-6b (Central PA, including Harrisburg): Plant mid-April to early May
- Zone 7a-7b (Southeastern PA, Philadelphia area): Plant early April to mid-April
Check your specific zone online if you’re unsure. Local extension offices also provide county-specific planting calendars.
Soil Temperature: The Real Trigger
Soil temperature is more reliable than air temperature. Asparagus crowns need soil at least 50°F to break dormancy and start root growth. Here’s how to measure it:
- Buy a soil thermometer (available at garden centers or online)
- Insert it 4 inches deep in your garden bed
- Take readings at the same time each morning for three consecutive days
- If the average is 50°F or higher, it’s time to plant
In Pennsylvania, soil warms up slower than air. A warm spell in March doesn’t mean the ground is ready. Wait for consistent readings. Cold frames or black plastic mulch can help warm the soil faster if you’re eager to start.
Preparing Your Asparagus Bed
Asparagus is a heavy feeder and needs deep, well-drained soil. Prepare your bed in the fall or at least two weeks before planting. Here’s what to do:
Site Selection
Choose a spot with full sun (at least 8 hours daily) and good drainage. Avoid low areas where water pools. Asparagus roots can rot in soggy soil. Raised beds work well in heavy clay soils common in parts of PA.
Soil Testing And Amendment
Test your soil pH. Asparagus prefers a pH between 6.5 and 7.5. In Pennsylvania, many soils are acidic. Add lime to raise pH if needed. Here’s a simple amendment plan:
- Spread 2-3 inches of compost over the bed
- Add 1-2 pounds of 10-10-10 fertilizer per 100 square feet
- Mix in lime or sulfur based on soil test results
- Remove all weeds, especially perennial ones like quackgrass
Work amendments into the top 12 inches of soil. Asparagus roots can grow 6 feet deep, but the top foot is critical for initial establishment.
Digging Trenches
Plant crowns in trenches 6-8 inches deep and 12-18 inches wide. Space trenches 4-5 feet apart to allow for mature fern growth. Here’s the step-by-step:
- Dig a trench 6 inches deep for sandy soils, 8 inches for clay
- Mound a small ridge of soil in the center of the trench
- Place crowns on the ridge, spreading roots downward
- Space crowns 12-18 inches apart within the trench
- Cover with 2 inches of soil initially
Don’t fill the trench completely at planting. As spears emerge, gradually fill in the trench over the growing season. This encourages deeper root growth.
Choosing Asparagus Varieties For PA
Not all asparagus varieties perform equally in Pennsylvania’s climate. Here are top performers for the state:
Jersey Series Hybrids
These are the most reliable for PA. They’re all-male hybrids, meaning no seed production and higher yields. Popular options include:
- Jersey Knight: High-yielding, disease-resistant, good for heavy soils
- Jersey Supreme: Early season, good for northern zones
- Jersey Giant: Thick spears, excellent for fresh eating
Other Reliable Varieties
If you prefer open-pollinated or heirloom types, consider:
- Mary Washington: Classic variety, but less disease-resistant than hybrids
- Purple Passion: Sweet, purple spears, but lower yields
- Millennium: Cold-hardy, good for northern PA
Stick with 1-year-old crowns for best establishment. Avoid 2-year-old crowns, as they often have damaged roots from transplanting.
Planting Step By Step
Follow this exact process for optimal results:
- Soak crowns in lukewarm water for 2-4 hours before planting
- Trim any broken or mushy roots with clean shears
- Place crowns on the soil ridge in the trench
- Spread roots evenly around the crown
- Cover with 2 inches of soil and water gently
- Mark rows with stakes to avoid walking on the bed
Water deeply after planting. Keep soil moist but not waterlogged for the first few weeks. Mulch with straw or wood chips to retain moisture and suppress weeds.
Caring For First-Year Asparagus
First-year care is different from established beds. Don’t harvest any spears the first year. Let all spears grow into ferns to build root energy. Here’s what to do:
Watering
Asparagus needs 1-2 inches of water per week during the growing season. In Pennsylvania, rainfall is often adequate, but supplement during dry spells. Drip irrigation is ideal to keep foliage dry and prevent disease.
Weed Control
Weeds compete heavily with young asparagus. Hand-pull weeds carefully to avoid disturbing roots. Mulch with 3-4 inches of straw or shredded leaves. Avoid using landscape fabric, as it can trap moisture and cause rot.
Fertilizing
Apply a balanced fertilizer (10-10-10) at a rate of 1 pound per 100 square feet in early June. Repeat in early August. Don’t over-fertilize, as this can encourage weak growth. Compost tea or fish emulsion are good organic options.
Winter Preparation
In Pennsylvania, winter protection is crucial. After the first hard frost, cut fern stalks down to 2 inches above the ground. Remove and compost the debris to reduce disease. Apply a 4-6 inch layer of straw or leaves for insulation. In northern PA, add an extra layer of row cover.
Harvesting In Subsequent Years
Patience pays off. Here’s the harvest timeline:
- Year 1: No harvest. Let all spears grow.
- Year 2: Harvest for 2-3 weeks. Stop when spears become thin.
- Year 3: Harvest for 4-6 weeks.
- Year 4+: Harvest for 8-10 weeks.
Harvest spears when they’re 6-8 inches tall. Snap them off at ground level. Stop harvesting when spear diameter drops below pencil-thickness. This signals the plant needs to store energy for next year.
Common Pennsylvania Challenges
Pennsylvania growers face specific issues. Here’s how to handle them:
Frost Damage
Late spring frosts can damage emerging spears. Cover beds with row cover or old sheets if frost is forecast. Damaged spears will be crooked or mushy. Cut them off and let new ones grow.
Diseases
Asparagus rust and fusarium wilt are common in PA. Prevent by:
- Planting resistant varieties (Jersey series)
- Ensuring good air circulation
- Avoiding overhead watering
- Rotating beds every 10-15 years
Pests
Asparagus beetles are the main pest. They lay eggs on spears and ferns. Hand-pick beetles and larvae. In severe cases, use insecticidal soap or neem oil. Clean up fern debris in fall to remove overwintering sites.
Frequently Asked Questions
Can I plant asparagus in fall in Pennsylvania?
Fall planting is not recommended in PA. Crowns need time to establish before winter. Spring planting gives them a full growing season to develop roots. Fall-planted crowns often heave out of the ground during freeze-thaw cycles.
How deep should I plant asparagus crowns in PA?
Plant crowns 6-8 inches deep, depending on soil type. Sandy soils need deeper planting (8 inches). Clay soils need shallower (6 inches). The goal is to have the crown 2 inches below the final soil level after filling the trench.
What is the best fertilizer for asparagus in Pennsylvania?
A balanced 10-10-10 fertilizer works well. Apply 1 pound per 100 square feet in early spring and again after harvest. Organic options include well-rotted manure, compost, or fish emulsion. Avoid high-nitrogen fertilizers that promote weak growth.
How long does it take for asparagus to grow from seed in PA?
Growing from seed takes 2-3 years before first harvest. Seeds should be started indoors 12-14 weeks before last frost. Transplant seedlings outdoors after soil warms. Most gardeners prefer 1-year-old crowns for faster results.
Can I plant asparagus in containers in Pennsylvania?
Container growing is possible but challenging. Use a 20-gallon pot at least 18 inches deep. Fill with well-draining potting mix. Container plants need more frequent watering and fertilizing. They may not survive harsh PA winters without protection.
Final Tips For Success
Planting asparagus in Pennsylvania requires patience and proper timing. Start with a well-prepared bed, choose the right variety, and wait for that 50°F soil temperature. Don’t rush the harvest in the first year. Your reward will be a productive bed that provides fresh spears for decades.
Keep a garden journal noting your planting date, variety, and any issues. This helps refine your approach each year. Join a local gardening group or contact your county extension office for region-specific advice. With the right care, your asparagus bed will be a source of pride and delicious harvests.