Should I use kale for winter? - Plant Care Guide

Yes, you should absolutely use kale for winter in your garden. Kale is one of the most cold-hardy vegetables, able to withstand significant frosts and even snow, making it an excellent choice for extending your harvest season well into the colder months. Its flavor often improves after a few touches of frost.

Why is Kale So Good for Winter Growing?

Kale is so good for winter growing primarily due to its exceptional cold hardiness and its ability to not only survive but often improve in flavor after exposure to cold temperatures. It's a powerhouse vegetable that keeps producing when many other crops have succumbed to frost.

Here's a breakdown of why kale excels in winter:

• Exceptional Cold Hardiness: Kale is a member of the Brassica oleracea family (along with cabbage, broccoli, and collards) but stands out as one of the most cold-tolerant. Many varieties can survive temperatures down to 10-20°F (-12 to -6°C), and some even lower, especially with a bit of protection like a row cover. It can withstand multiple frosts and even being covered in snow.
• Improved Flavor After Frost: This is a unique and highly desirable trait. Exposure to cold temperatures triggers kale to convert starches into sugars (a natural antifreeze mechanism). This process results in kale leaves becoming noticeably sweeter and less bitter, often with a more tender texture, after they've experienced a few frosts. This makes it more palatable for fresh eating.
• Continuous Harvest: Unlike many vegetables that die back after the first frost, kale can provide a continuous harvest of outer leaves throughout much of the winter, providing fresh greens when other garden produce is scarce. You can pick leaves as needed, and the plant will continue to produce from the center.
• Nutritional Powerhouse: Even in winter, kale continues to be packed with vitamins (A, C, K), minerals, and antioxidants. Harvesting fresh, nutritious greens in the coldest months is a significant benefit to winter health.
• Low Maintenance in Cold: Once established for winter, kale generally requires less pest management (as many pests are dormant) and less frequent watering compared to summer crops.

For these reasons, kale is a stellar choice for extending the gardening season and enjoying fresh, homegrown vegetables even in the depths of winter.

What Are the Best Kale Varieties for Winter Harvest?

The best kale varieties for winter harvest are those specifically known for their exceptional cold hardiness and improved flavor with frost. While most kales are cold-tolerant, some perform better than others in deep winter conditions.

Here are some top varieties for winter production:

1. 'Winterbor' (Siberian Type):
   • Characteristics: Known for its highly ruffled, dark green, deeply curled leaves. It's exceptionally cold-hardy, capable of surviving very harsh winters.
   • Flavor: Flavor sweetens significantly after frost.
   • Growth Habit: Upright, making it easy to harvest outer leaves.
2. 'Red Russian' (Siberian Type):
   • Characteristics: Features flat, deeply lobed, often purple-veined leaves that develop a beautiful reddish-purple hue in cold weather. It's very cold-hardy.
   • Flavor: Tends to be sweeter and more tender than some other kales, improving further with frost.
   • Appearance: Adds ornamental value to the winter garden with its striking color.
3. 'Lacinato' / 'Dinosaur' / 'Tuscan' (Cavolo Nero Type):
   • Characteristics: Distinctive, dark blue-green, heavily textured (savoyed) leaves that resemble dinosaur skin. It's quite cold-hardy, surviving well in most mild winter regions and even moderate freezes.
   • Flavor: Has a robust, slightly nutty flavor that also sweetens with frost. It holds up well in cooking.
4. 'Blue Curled Scotch':
   • Characteristics: Classic, very tightly curled, blue-green leaves. It's a reliable cold-hardy choice.
   • Flavor: Good, classic kale flavor that sweetens with cold.
   • Growth Habit: Very ornamental, bushy growth.
5. 'Redbor' (Ornamental/Edible):
   • Characteristics: Striking, intensely dark purple to red, highly ruffled leaves. Often grown as an ornamental due to its dramatic color but is fully edible and quite cold-hardy.
   • Flavor: Good flavor, becomes sweeter in cold.
   • Appearance: Provides excellent color in the winter garden.

When selecting, consider your specific USDA Hardiness Zone. For colder regions, prioritize varieties like 'Winterbor' or 'Red Russian'. For milder winters, 'Lacinato' is an excellent choice. Look for kale seeds for cold weather from reputable seed suppliers.

When Should I Plant Kale for Winter Harvest?

You should plant kale for winter harvest in late summer to early fall, typically about 6-8 weeks before your first expected hard frost. This timing allows the plants to establish a good root system and develop enough foliage before temperatures drop significantly and growth slows down.

Here's a more detailed breakdown:

• Regional Timing:
  • Cooler Climates (Zones 5-6): Aim for planting in late July to mid-August.
  • Moderate Climates (Zones 7-8): Plant in August to early September.
  • Warmer Climates (Zones 9-10+): You have a longer window, often from September through October, or even later for a continuous winter harvest.
• Target "Hardening Off": The goal is to have the kale plants be fairly well-developed (with a few sets of true leaves) by the time the first light frosts begin. This allows them to "harden off" and gradually adapt to cooler temperatures, making them more resilient.
• Seed vs. Transplant:
  • Direct Sowing: Sow kale seeds directly into your garden bed. Plant them about 1/2 inch deep and 6-12 inches apart, depending on the mature size of the variety.
  • Transplants: If your growing season is short or you're starting later, you can sow seeds indoors 4-6 weeks before your outdoor planting date and then transplant seedlings into the garden. Transplants give you a head start.
• Benefits of Fall Planting:
  • Avoiding Summer Pests: Many common kale pests (like cabbage worms, aphids) are less active in the cooler fall temperatures.
  • Milder Conditions: The decreasing temperatures are less stressful for germinating seeds and young plants compared to the heat of summer.
  • Improved Flavor: Planting in late summer/early fall ensures the plants will experience cold temperatures by the time they are mature enough for harvest, leading to sweeter leaves.
• Succession Planting: For a continuous harvest throughout winter, you can do succession planting, sowing smaller batches of kale seeds every 2-3 weeks in late summer and early fall.

By timing your planting correctly, you give your kale the best chance to establish robustly and provide a continuous supply of fresh, delicious greens throughout the winter months.

How Can I Protect Kale in Harsh Winter Conditions?

While kale is exceptionally cold-hardy, you can protect kale in harsh winter conditions to extend your harvest season even further and ensure plant survival in very cold climates. These methods create a microclimate that offers additional insulation against extreme cold, drying winds, and heavy snow.

Here's how to provide protection:

1. Mulch Heavily:
   • Purpose: A thick layer of mulch around the base of the kale plants helps to insulate the soil, protecting the roots from deep freezes and preventing damaging freeze-thaw cycles.
   • Application: Apply 4-6 inches of organic mulch (like straw, shredded leaves, or untreated wood chips) around the plant crowns in late fall, once temperatures consistently drop. Keep the mulch a few inches away from the actual stem to prevent rot.
2. Floating Row Covers:
   • Purpose: These lightweight fabric covers create a few degrees of warmth (typically 2-10°F or 1-6°C) around the plants and protect against wind, heavy snow, and drying effects.
   • Application: Drape floating row covers directly over the kale plants. Anchor the edges with rocks, soil, or pins to prevent wind from lifting them. You can use hoops to keep the fabric off the leaves for better air circulation if desired.
   • Benefits: Still allows light and water to penetrate. Easily removed for harvesting.
3. Cold Frames:
   • Purpose: A cold frame is a bottomless box with a transparent lid that sits over plants, trapping solar heat during the day and insulating them at night.
   • Application: Build or purchase a cold frame and place it over your kale plants. Prop open the lid on sunny days to prevent overheating and provide ventilation, then close it at night.
   • Benefits: Provides significant protection, extending the season well into deep winter.
4. Cloches or Bell Jars:
   • Purpose: Individual covers (glass or plastic) that can protect single plants or small clusters.
   • Application: Place over individual kale plants. Prop open on sunny days.
   • Benefits: Targeted protection for a few plants.
5. Hoop Tunnels:
   • Purpose: A larger version of row covers, using flexible hoops to create a tunnel over a row of plants, then covering with plastic sheeting or heavy row cover fabric.
   • Application: Install hoops over your kale row and drape the chosen covering material. Secure the edges.
   • Benefits: Excellent for larger rows, providing more interior space and potentially better insulation than flat row covers.
6. Location Selection:
   • Plant kale in a sunny, sheltered spot in your garden, perhaps against a south-facing wall or fence that will absorb and radiate heat.
7. Container Growing (for portability):
   • If growing kale in containers, you can move them to a more protected location during severe cold snaps (e.g., against the house, into an unheated garage, or into a cold frame).

By combining some of these protection methods, you can push kale's already impressive cold tolerance even further, ensuring a longer and more reliable winter harvest.

What Are the Best Harvesting Techniques for Winter Kale?

The best harvesting techniques for winter kale focus on preserving the plant's health, encouraging continuous production, and adapting to slower growth in cold temperatures. Unlike summer harvesting, where growth is rapid, winter harvesting requires a more conservative approach.

Here are the key techniques:

1. "Cut-and-Come-Again" Method (Outer Leaf Harvest):
   • Most Common & Recommended: This is the primary method for continuous winter harvest.
   • How to Do It: Harvest only the outer, lower leaves of the kale plant. Snap or cut them off cleanly at the stem base, taking care not to damage the central growing point (the crown) of the plant.
   • Benefits: This encourages the plant to continue producing new leaves from the center, ensuring a sustained supply of greens over several weeks or months. It also maintains the plant's overall health by preventing it from becoming top-heavy.
2. Harvest as Needed:
   • In winter, plant growth slows significantly. Harvest only what you need for immediate use, rather than taking large quantities at once. This reduces stress on the plant.
3. Avoid Harvesting the Central Crown:
   • The central cluster of leaves at the top of the plant is the main growing point. Do not cut this area, as it is essential for the plant's continued survival and future production.
4. Remove Yellowing or Damaged Leaves:
   • As you harvest, also remove any leaves that are yellowing, damaged by frost (turning mushy or black), or show signs of disease. This redirects the plant's energy to healthy growth.
5. Harvest in the Mid-Day:
   • If temperatures have been below freezing, try to harvest in the middle of the day after the plant has had a chance to thaw out naturally. Harvesting frozen leaves can damage the plant and affect leaf texture.
6. Leave Some Foliage:
   • Always leave a good number of healthy, established inner leaves on the plant, especially those protecting the central crown. These leaves are vital for photosynthesis and allowing the plant to store energy for continued survival and new growth.
7. Tools:
   • Use clean, sharp pruning shears or a sharp knife for clean cuts.
8. Patience in Deep Winter:
   • During periods of extreme cold or deep snow cover, growth will almost stop. The plant is simply trying to survive. You might only be able to harvest a few leaves at a time or might need to wait for a brief warming spell.

By following these harvesting techniques, you can enjoy fresh kale from your garden throughout much of the winter, maximizing its yield and ensuring the plant remains healthy for as long as possible.

How Does Frost Affect the Flavor of Kale?

Frost significantly affects the flavor of kale by making it noticeably sweeter and less bitter. This improvement in taste is a unique and highly desirable characteristic of kale and other hardy brassicas grown in cold weather.

Here's the scientific reason behind this phenomenon:

• Conversion of Starches to Sugars: Plants, including kale, produce and store starches (complex carbohydrates) during their growing season. When temperatures drop and approach freezing, the plant's natural defense mechanism against ice crystal formation kicks in. This mechanism involves converting the stored starches into simpler sugars.
  • Sugars as Antifreeze: Sugars act as a natural "antifreeze" within the plant's cells, lowering the freezing point of the cell sap. This helps prevent severe ice damage that would rupture cell walls.
  • Sweetness Boost: The increased concentration of these sugars directly translates to a sweeter taste for human consumption.
• Reduced Bitterness: The cold also appears to mellow or break down some of the compounds that contribute to kale's characteristic bitterness. This makes the flavor rounder and more palatable, especially for raw consumption.
• Texture Improvement (Often): While primary cold damage can make leaves mushy, a light to moderate frost can sometimes contribute to a slightly more tender texture, making the leaves less tough.

Practical Implications for Gardeners:

• Wait for Cold: Many gardeners intentionally wait until after the first few frosts to begin harvesting their main kale crop, specifically to enhance the flavor.
• Optimal Timing: The "sweetest" kale often comes after temperatures have dropped below freezing for a few nights but before a prolonged, hard freeze severely damages the foliage.
• Eating Raw: Frost-kissed kale is often preferred for salads or smoothies due to its milder, sweeter flavor.

So, for kale, a touch of cold is not a detriment but actually a secret ingredient that enhances its culinary appeal, making it even more desirable for winter harvests.

What Other Crops Can I Grow for Winter Harvest with Kale?

Alongside kale, there are several other cold-hardy crops you can grow for winter harvest, extending your garden's productivity well beyond the traditional growing season. Many of these, like kale, also benefit from a touch of frost.

Here are some excellent companions for winter harvest:

1. Collard Greens:
   • Hardiness: Very similar to kale in cold tolerance, often surviving into the low teens Fahrenheit.
   • Growth: Produce large, flat leaves. Harvest using the "cut-and-come-again" method.
   • Flavor: Sweetens significantly after frost.
2. Swiss Chard:
   • Hardiness: Tolerates light to moderate freezes (down to 15-20°F or -9 to -6°C). May die back in harder freezes but often resprouts in spring.
   • Growth: Beautiful, colorful stems and large leaves.
   • Harvest: Pick outer leaves.
3. Spinach:
   • Hardiness: Good cold tolerance, especially 'Tyee' or 'Bloomsdale Long Standing' varieties, surviving down to 10-15°F (-12 to -9°C) with some protection.
   • Growth: Can overwinter as small plants and then grow rapidly in early spring.
   • Harvest: Pick individual leaves or cut whole plants.
4. Arugula:
   • Hardiness: Surprisingly cold-tolerant, surviving light frosts and even snow, often down to 15-20°F (-9 to -6°C).
   • Growth: Adds a peppery kick to winter salads.
   • Harvest: Cut-and-come-again.
5. Mache (Corn Salad):
   • Hardiness: Extremely cold-hardy, surviving even colder temperatures than kale (sometimes down to 0°F or -18°C) with protection.
   • Growth: Forms small, tender rosettes.
   • Flavor: Mild, nutty flavor, excellent for winter salads.
6. Brussels Sprouts:
   • Hardiness: Very cold-hardy; actually taste better after a few hard frosts.
   • Growth: Sprouts develop along a tall stalk.
   • Harvest: Harvest sprouts from the bottom up as they mature.
7. Carrots:
   • Hardiness: Can be left in the ground through winter in many zones, surviving under mulch or snow. Freezing temperatures convert starches to sugars.
   • Growth: Root vegetable.
   • Harvest: Dig as needed, or wait until early spring for sweetest flavor.
8. Parsnips:
   • Hardiness: Even more cold-hardy than carrots. Flavor dramatically improves after hard frosts.
   • Growth: Root vegetable.
   • Harvest: Leave in ground all winter and harvest in early spring.
9. Leeks:
   • Hardiness: Very tolerant of cold and light freezes.
   • Growth: Allium relative.
   • Harvest: Dig as needed throughout winter.

By planning and planting these cold-hardy crops, you can transform your winter garden into a productive and nutritious resource, complementing your kale harvest. Many of these benefit from similar winter protection methods like row covers or cold frames.