Yes you can use plastic bag plant protection for your small plants but be careful. This method works only if you follow key rules. Never let your plastic touch the leaves directly. When I first tried this the plastic contact caused worse damage than the frost itself.
The material transfers cold straight to foliage when they touch. Plastic bag frost cover methods fail when people drape bags directly onto plants. Anywhere the plastic contacts a leaf will show frost damage. Those spots freeze faster than uncovered leaves would.
Support the bag above your plant using small stakes or sticks. Push 3 or 4 stakes into the soil around the plant. Drape the plastic over them to create a mini greenhouse shape. This air gap between plastic and leaves provides the insulation you need.
The trapped air prevents cold transfer and protects your foliage. When you put a bag over plant frost protection this way it actually works. The key is that air gap. Without it you cause more harm than good.
Remove plastic bags each morning without exception. Sun heats up plastic fast and can cook your plants by midday. I set a phone alarm for every morning during frost season. Condensation also builds up overnight inside the bag.
Removing the bag lets moisture escape and air circulate. Trapped moisture can freeze and cause its own damage. You need to take action both evening and morning with plastic bag covers.
Plastic bags work okay for emergency frost protection if you have nothing else. I have used grocery bags over small pepper plants when frost hit fast. They kept my plants alive through the night when I had no other option.
But this should be a last resort rather than your main protection strategy. Fabric covers work better than plastic for most frost protection needs. Sheets and blankets breathe naturally and prevent moisture problems.
Fabric also insulates well without your risk of leaf contact damage. You do not need to support fabric above your plants like you do with plastic. Save your plastic bags for wrapping pots or true emergencies when you have no other choice.
Use cloth for covering your foliage when you can. Keep a stash of old sheets and blankets ready for your garden at all times. They work better and cause fewer problems than plastic bags. I tested both methods many times and cloth wins every single time.
Read the full article: Protecting Plants from Frost That Works
