Kale Mastery: Varieties, Succession Planting & Season Extension

Beyond the Basics: Intermediate Kale Growing

You've grown kale successfully and experienced its easy-going nature. Now it's time to optimize your production for continuous harvests, explore the rich diversity of varieties, and implement season extension techniques that can provide fresh kale nearly year-round in most climates.

Deep Dive into Kale Varieties

Curly Kale Cultivars

Winterbor (Hybrid)

• Most cold-hardy curly type
• Deep blue-green, tightly curled leaves
• Plants reach 24-30 inches tall
• Maintains quality in field for extended periods
• Days to maturity: 60
• Best for: Overwintering, commercial production

Dwarf Blue Curled Scotch (Vates)

• Compact plants (12-16 inches)
• Blue-green, finely curled leaves
• Excellent cold tolerance
• Days to maturity: 55
• Best for: Small gardens, containers

Redbor (Hybrid)

• Stunning deep purple-red color
• Intensifies color with cold
• Tall plants (24-30 inches)
• Days to maturity: 55
• Best for: Ornamental edible gardens, fall color

Darkibor (Hybrid)

• Extremely dark green, almost black
• Excellent uniformity
• Good baby leaf variety
• Days to maturity: 50
• Best for: Market production, baby leaf

Lacinato (Dinosaur) Varieties

Lacinato/Nero di Toscana

• Classic Italian heirloom
• Dark blue-green savoyed leaves
• 18-24 inches tall, narrow profile
• Sweetest flavor of all kales
• Days to maturity: 60-65
• Best for: Culinary use, Italian dishes

Black Magic

• Improved lacinato type
• More heat tolerant than traditional
• Uniform, upright growth
• Days to maturity: 65
• Best for: Warm climate growers

Rainbow Lacinato

• Cross between Lacinato and Redbor
• Multicolored: blue-green, purple, pink
• Color deepens in cold weather
• Days to maturity: 60
• Best for: Visual appeal, specialty markets

Red/Russian Varieties

Red Russian

• Flat, oak-shaped leaves
• Gray-green with purple-red stems
• Most tender and mild kale
• Extremely cold hardy (to -10°F/-23°C)
• Days to maturity: 50
• Best for: Salads, overwintering

Scarlet Kale

• Intensely purple-red
• Frilly leaf edges
• Compact growth
• Days to maturity: 60
• Best for: Baby leaf, color contrast

Specialty Varieties

White Russian

• Gray-green leaves with white stems
• Oak-leaf shape like Red Russian
• Very tender and sweet
• Days to maturity: 50

Siberian Kale

• Large, smooth-edged leaves
• Extremely cold tolerant
• Mild, tender flavor
• Often harvested as baby greens
• Days to maturity: 50

Succession Planting Strategy

The Succession Planting Calendar

Continuous Harvest Plan

Goal: Fresh kale year-round

1. Plant every 3-4 weeks from early spring through mid-summer
2. Switch varieties based on season:
   • Spring: Fast-maturing, bolt-resistant
   • Summer: Heat-tolerant varieties
   • Fall: Cold-hardy types for overwintering
3. Stagger harvest by taking outer leaves from multiple plantings

Example Schedule (Zone 6)

Season Extension Techniques

Cold Frame Growing

Cold frames extend the season 4-6 weeks in spring and fall:

Design specifications:

• South-facing orientation
• Back wall 12-18 inches high
• Front wall 6-8 inches high
• Transparent lid (glass or polycarbonate)
• Ventilation capability

Management:

• Open lid when interior exceeds 70°F (21°C)
• Close before sunset to trap heat
• Add blankets on coldest nights
• Water sparingly in winter

Temperature gains:

• Daytime: 10-30°F higher than outside
• Nighttime: 5-10°F higher

Low Tunnel (Row Cover) System

Materials:

• Wire hoops or PVC pipe (5-7 feet long)
• Row cover fabric (various weights)
• Sandbags or soil to anchor edges

Cover weight selection:

• Light (0.5 oz/sq yd): Pest protection, minimal frost
• Medium (1.25 oz/sq yd): 4-6°F frost protection
• Heavy (2.0 oz/sq yd): 6-8°F frost protection, overwinter

Benefits for kale:

• Extends season 3-4 weeks each direction
• Protects from pest pressure
• Allows moisture and 70-85% light transmission

Overwintering Kale

Kale can survive winter in zones 7+ (and zones 5-6 with protection):

Site preparation:

• Choose protected location (south-facing, near building)
• Well-drained soil prevents root rot
• Add 4-6 inches mulch around plants after hard freeze

Variety selection for overwintering:

• Winterbor (curly)
• Red Russian (most cold-hardy)
• Siberian

Spring harvest:

• Plants resume growth when temperatures exceed 40°F
• Harvest quickly before bolting
• Remove plants when flower stalks appear

Pro Tip: Fall-planted kale allowed to overwinter produces the sweetest, most tender leaves in early spring—often sweeter than any other time of year.

Integrated Pest Management (IPM)

Understanding the Pest Calendar

Biological Controls

Bacillus thuringiensis (Bt):

• Targets caterpillars specifically
• Apply when worms are young and actively feeding
• Reapply after rain
• Safe for beneficial insects

Beneficial insects to encourage:

• Lady beetles (aphid predators)
• Parasitic wasps (caterpillar parasites)
• Lacewings (aphid and caterpillar predators)
• Ground beetles (soil pest predators)

Attracting beneficials:

• Plant alyssum, yarrow, fennel nearby
• Provide water sources
• Avoid broad-spectrum pesticides
• Leave some wild areas in garden

Physical Controls

Row covers:

• Most effective method for brassica pests
• Apply immediately after planting/transplanting
• Seal edges completely
• Remove only for harvesting or pollination (not needed for kale)

Hand-picking:

• Check plants 2-3 times per week
• Look under leaves for caterpillars and eggs
• Drop pests in soapy water
• Most effective in morning when pests are sluggish

Companion planting:

• Interplant with strong-scented herbs (thyme, sage, rosemary)
• Use trap crops (nasturtiums attract aphids away)
• Avoid planting near other brassicas

Disease Prevention and Management

Downy Mildew (Hyaloperonospora parasitica)

Identification:

• Yellow patches on upper leaf surface
• White to grayish mold on leaf undersides
• Spreads rapidly in cool, wet conditions

Prevention:

• Space plants for good air circulation
• Avoid overhead watering
• Plant resistant varieties
• Rotate crops (2-3 year rotation)

Management:

• Remove infected leaves promptly
• Apply copper-based fungicides preventatively
• Improve drainage and air circulation

Black Rot (Xanthomonas campestris)

Identification:

• V-shaped yellow lesions from leaf margins
• Lesions turn brown/black
• Dark veins visible in affected tissue
• Bacterial, spreads in water

Prevention:

• Use certified disease-free seed
• Hot water seed treatment (122°F for 25 minutes)
• Avoid working with wet plants
• Rotate crops for 3+ years

Clubroot (Plasmodiophora brassicae)

Identification:

• Swollen, distorted roots
• Wilting despite adequate moisture
• Stunted growth
• Soil-borne, persists for 10+ years

Prevention:

• Test soil before planting in new areas
• Raise soil pH above 7.2 (clubroot prefers acidic soils)
• Avoid transplanting from infected areas
• Use resistant varieties if available

Optimizing Harvest Quality

Timing Harvest for Best Flavor

Factors affecting sweetness:

• Cold exposure converts starches to sugars
• Morning harvest has highest sugar content
• Younger leaves are more tender
• Overmaturity increases bitterness

Optimal harvest timing:

• Wait until after first frost for sweetest flavor
• Harvest in morning after dew dries
• Pick leaves at 8-12 inches for best quality
• Avoid harvesting heat-stressed plants

Post-Harvest Handling

Immediate handling:

• Harvest into clean containers
• Move to shade immediately
• Cool as quickly as possible
• Aim for 32-34°F (0-1°C) storage

Storage for maximum quality:

• Temperature: 32°F (0°C)
• Relative humidity: 95-98%
• Shelf life: 10-14 days at optimal conditions
• Don't wash until ready to use

Hydrocooling:

• Submerge harvested kale in ice water
• Rapidly reduces field heat
• Maintains crispness
• Essential for market growers

Variety Trial Recommendations

Taste Test Categories

Sweetest flavor:

1. Lacinato (after frost)
2. Red Russian
3. Siberian

Best for raw salads:

1. Red Russian
2. Baby leaf varieties
3. White Russian

Best cooking kale:

1. Winterbor
2. Lacinato
3. Redbor

Most ornamental:

1. Redbor
2. Rainbow Lacinato
3. Ornamental varieties

Cold Hardiness Ranking

Quick Reference: Intermediate Techniques

Next Level

Ready to advance further? The Advanced guide covers:

• Commercial production techniques
• Intensive planting systems
• Advanced IPM protocols
• Fertigation and drip irrigation
• Post-harvest handling for market
• Season extension structures
• Variety trialing methodology