Intermediate Leek Growing: Varieties, Blanching & Season Extension

Intermediate Leek Growing: Varieties, Blanching & Season Extension

Ready to advance your leek-growing skills? This intermediate guide explores the full spectrum of leek varieties, teaches advanced blanching techniques, and reveals strategies for extending your harvest from summer through winter. Whether you're growing for your family or farmers market, these techniques will elevate your leek production.

Comprehensive Variety Selection

Understanding Leek Classifications

Leeks are typically classified by harvest season and cold-hardiness:

Summer/Early Types:

• Mature in 75-100 days
• Lighter green leaves
• Less winter-hardy
• Best for fresh eating

Fall Types:

• Mature in 100-130 days
• Darker green leaves
• Moderate cold tolerance
• Good all-purpose

Winter Types:

• Mature in 130-150+ days
• Blue-green leaves
• Very cold-hardy (some to -10°F)
• Best for overwintering

Detailed Variety Guide

Summer/Early Varieties:

Fall Varieties:

Winter Varieties:

Variety Selection Strategy

For Continuous Harvest: Plant a mix of early, mid, and late varieties:

• Early: 'King Richard' (summer harvest)
• Mid: 'Chinook' or 'Giant Musselburgh' (fall harvest)
• Late: 'Bandit' or 'Tadorna' (winter/spring harvest)

For Market Sales: Focus on uniformity and disease resistance:

• 'Chinook': Very uniform, disease-resistant
• 'Megaton': Large, impressive shanks
• 'King Richard': Excellent for baby leeks

Advanced Blanching Techniques

Deep Trench Method

Initial Setup:

1. Dig trenches 12 inches deep, 6 inches wide
2. Add 3-4 inches of compost at bottom
3. Set transplants at trench bottom
4. Cover only the root zone initially

Progressive Filling:

Collar Method (No Hilling Required)

Materials:

• 4-6" sections of PVC pipe, cardboard tubes, or newspaper collars
• Alternatively: toilet paper tubes, paper towel tubes

Process:

1. Transplant at normal depth
2. When stems are pencil-thick, place collar around base
3. Collar should extend 4-6 inches above soil
4. As leeks grow, add additional collars or replace with longer ones

Advantages:

• No soil between leaf layers
• Cleaner harvests
• Good for clay or rocky soils

Mulch Blanching

Deep Mulch Technique:

1. Transplant at soil level
2. Apply 6-8 inches of straw or leaves around plants
3. Continue adding mulch as plants grow
4. Mulch blanches AND insulates for winter

Materials:

• Straw (best for cleanliness)
• Shredded leaves
• Wood shavings (not fresh, which can deplete nitrogen)

Succession Planting

Planting Schedule (Zones 5-7)

Multi-Season Planning

For Year-Round Production:

Soil and Nutrient Management

Soil Preparation

Ideal Soil Profile:

• Deep (12-18 inches of loose soil)
• Rich in organic matter (5-7%)
• Well-draining but moisture-retentive
• pH 6.2-6.8

Pre-Plant Amendments (per 100 sq ft):

• Compost: 3-4 cubic feet
• Balanced organic fertilizer: 2-3 lbs
• Bone meal: 1 lb (phosphorus)
• Greensand: 2 lbs (potassium)

Fertilization Program

Total Season Nitrogen Needs: 150-200 lbs N/acre (3.5-4.5 lbs/100 sq ft)

Application Schedule:

Micronutrient Considerations

Important Micronutrients for Leeks:

• Sulfur: Flavor development (use gypsum if deficient)
• Boron: Cell wall development (1-2 lbs borax/acre if needed)
• Zinc: Growth vigor

Pest and Disease Management

Integrated Pest Management

Thrips (Thrips tabaci): Most common pest of leeks.

Control Strategies:

• Reflective mulch (deters adults)
• Overhead irrigation (disrupts life cycle)
• Spinosad or neem (organic options)
• Blue sticky traps for monitoring

Allium Leafminer (Phytomyza gymnostoma): Invasive pest causing up to 98% damage if uncontrolled.

Identification:

• Adults: Small yellow-headed flies
• Mining: Wavy lines on leaves
• Pupae: Orange-brown, in tissue

Control:

• Row covers during flight periods (March-May, September-October)
• Destroy affected plant material
• No effective organic sprays

Disease Prevention

Leek Rust (Puccinia allii): Most common disease in humid climates.

Prevention:

• Resistant varieties (Autumn Giant, Megaton)
• Wide spacing for air circulation
• Avoid overhead irrigation
• Remove affected leaves
• Sulfur sprays (preventive)

White Rot (Sclerotium cepivorum): Devastating soil-borne disease.

Overwintering Techniques

In-Ground Overwintering

Requirements:

• Winter-hardy varieties (Bandit, Tadorna, Bleu de Solaise)
• Heavy mulch (8-12 inches)
• Good drainage (prevent crown rot)

Process:

1. Apply 6-8 inches of straw after first hard frost
2. Add more after ground begins to freeze
3. Total: 10-12 inches of mulch
4. Harvest as needed by pulling back mulch
5. Can harvest through snow if mulch is adequate

Cold Frame Overwintering

Advantages:

• Protection to -10°F or below
• Easier harvest access
• Extended harvest into March

Setup:

1. Transplant into cold frame in July-August
2. Use winter-hardy varieties
3. Close frame when temps drop below 20°F
4. Ventilate on sunny days above 40°F

Row Cover Systems

Low Tunnel Method:

1. Install wire hoops over leek rows
2. Cover with heavy row cover (1.5 oz) after first frost
3. Add second layer for extreme cold
4. Harvest by lifting covers as needed

Troubleshooting Intermediate Issues

Problem: Rust spreading rapidly

• Cause: Humid conditions, susceptible variety
• Solution: Remove affected leaves, improve air circulation, switch to resistant varieties

Problem: Leeks not sizing up

• Cause: Insufficient nutrition, competition, or water stress
• Solution: Side-dress with nitrogen, ensure adequate spacing, consistent irrigation

Problem: Hollow or pithy centers

• Cause: Bolting initiation, heat stress, or over-maturity
• Solution: Harvest earlier, provide shade in heat, maintain consistent conditions

Problem: Significant winter kill despite cold-hardy varieties

• Cause: Inadequate mulch, ice damage, or crown rot
• Solution: More mulch, improve drainage, ensure varieties are truly winter-hardy

Next Steps: Advancing Your Skills

Ready for more advanced techniques? Consider:

1. Commercial production systems
2. Seed saving from overwintered plants
3. Breeding for local adaptation
4. Season-long market production

With these intermediate techniques, you'll achieve consistent, high-quality leek harvests from summer through early spring.