Protecting kale from freezing temperatures ensures your crop survives cold snaps and harsh winters, preserving its flavor and nutritional value. Kale is a hardy leafy green, often able to tolerate cold better than many vegetables, but extreme freezes can damage its leaves and reduce yield. With proper preparation and protection techniques, you can extend your kale harvest well into the colder months. Before you begin, assess your garden’s exposure to wind and frost pockets, and gather any materials you’ll use to shield your plants.
What You’ll Need
- Frost cloths or row covers (lightweight fabric designed for frost protection)
- Mulch (straw, shredded leaves, or wood chips)
- Garden stakes or hoops (to support covers)
- Watering can or hose (to moisten soil before frost)
- Optional: Cloche or cold frame (for small-scale protection)
- Optional: Burlap or old sheets (if frost cloths are unavailable)
Step-by-Step
- Monitor Weather Forecasts: Start by keeping an eye on local weather reports for frost warnings or freezing temperatures. This allows you to prepare your kale plants in advance.
- Water the Soil Thoroughly: Before a cold night, water the soil around your kale plants. Moist soil retains heat better than dry soil, helping to moderate root temperatures overnight.
- Apply Mulch Around the Base: Spread a 2-3 inch layer of organic mulch such as straw, shredded leaves, or wood chips around the base of each kale plant. This insulates the roots and prevents soil from freezing quickly.
- Set Up Support for Covers: Use garden stakes or wire hoops to create a frame over your kale bed. This prevents frost cloths or row covers from resting directly on the leaves, which can cause damage.
- Cover Kale with Frost Cloth or Row Covers: Drape frost cloths or lightweight row covers over the supports, extending the fabric to the ground on all sides to trap warm air. Secure the edges with soil, rocks, or clips to prevent cold air from entering.
- Use Cloches or Cold Frames for Small Plants: For individual plants or small batches, place cloches (plastic or glass domes) or cold frames over kale. These provide a mini-greenhouse effect, maintaining warmer air around the leaves.
- Remove Covers During Daylight Hours: On sunny days, remove or open covers to allow airflow and prevent overheating. Excess moisture buildup under covers can promote disease.
- Inspect Plants Regularly: Check your kale daily for signs of frost damage or moisture issues. Adjust covers or mulch as needed to maintain protection.
- Harvest Leaves as Needed: If a hard freeze is expected and your kale is mature, consider harvesting some leaves beforehand. Kale often tastes sweeter after frost but severe freezes can cause damage.
- After the Freeze: Once freezing temperatures subside, gradually remove protection to avoid sudden temperature shock. Continue regular care to support recovery.
Common Mistakes
- Using Plastic Directly on Leaves: Plastic sheeting placed directly on kale can freeze the leaves and cause damage. Always use breathable frost cloth or create a frame to keep covers off the foliage.
- Not Securing Covers Properly: Loose covers can blow away or allow cold air inside, reducing protection. Make sure edges are sealed well each night.
- Overwatering Before Frost: While moist soil is beneficial, waterlogged soil can lead to root rot and other diseases, especially under covers. Water moderately and ensure good drainage.
- Leaving Covers On During Sunny Days: Failing to remove or vent covers during the day can cause overheating and fungal problems.
- Ignoring Mulch: Neglecting to mulch leaves roots vulnerable to freezing, even if the foliage is covered.
Tips
- Plant kale in a location with good sun exposure and some wind protection to naturally reduce frost risk.
- Choose cold-hardy kale varieties like ‘Winterbor’ or ‘Red Russian’ for better freeze tolerance.
- Layer frost covers if extremely low temperatures are forecasted for extra insulation.
- Use old sheets or burlap as emergency frost covers, but be sure to remove them in the morning to prevent moisture buildup.
- Consider planting kale near heat-retaining structures like south-facing walls to provide microclimate warmth.
- Harvest leaves promptly after frost events to enjoy the sweeter flavor kale develops.
Troubleshooting
If Kale Shows Signs of Freeze Damage: Damaged kale leaves may become wilted, blackened, or mushy. Remove any severely damaged leaves promptly to prevent disease. Healthy leaves often recover after a few days when temperatures rise.
If Frost Covers Are Blown Away: Reinforce covers with heavier weights or stakes, and check them regularly during windy nights. Consider securing covers with garden staples or clips for added stability.
If Mold or Mildew Develops Under Covers: This usually results from poor ventilation or excessive moisture. Remove covers during the day to allow airflow and reduce watering frequency. Avoid covering wet plants.
If Roots Appear Damaged Despite Protection: Check soil drainage and reduce watering. Consider adding thicker mulch layers or using cold frames for better root insulation.
If Kale Freezes Despite Precautions: For future protection, increase the thickness of mulch and use multiple layers of frost cloth. Also, try to harvest mature leaves before severe freezes.
Frequently Asked Questions
Can kale survive a light frost?
Kale is frost-tolerant and can survive light frosts, often becoming sweeter after exposure. However, prolonged or severe freezes may damage leaves.
Is it better to cover kale at night or all day during cold spells?
Cover kale at night to protect from freezing temperatures, but remove or vent covers during sunny days to prevent overheating and moisture buildup.
What is the best mulch for protecting kale roots from freezing?
Straw, shredded leaves, or wood chips are excellent mulches that insulate soil and retain moisture, protecting roots from freezing.
Can I use plastic sheeting to protect kale from frost?
Plastic can cause leaf damage if placed directly on plants. Use breathable frost cloths or create a frame to keep plastic off the foliage if using it.
How low can temperatures go before kale is seriously damaged?
Kale can tolerate temperatures down to about 20°F (-6°C) but sustained exposure below this can cause severe leaf damage or plant death without protection.
Does kale taste better after a frost?
Yes, exposure to frost converts some starches into sugars, making kale taste sweeter and less bitter.
Can I leave frost covers on kale all winter?
It’s best to remove covers during the day for airflow and to prevent disease. For long-term winter protection, consider cold frames or greenhouses.
How often should I check my kale during freezing weather?
Check daily, especially at night and early morning, to ensure covers remain secure and plants are not showing signs of damage.
By following these steps and tips, you can effectively protect your kale from freezing temperatures and enjoy fresh, nutritious greens even in the coldest months. Proper preparation, timely action, and regular monitoring are key to successful winter gardening with kale.
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