Yes bed sheet frost protection works quite well for light frost events. A simple sheet adds around 3 to 4 degrees of warmth to your plants. When I first tried this method I saved tomatoes peppers and basil with nothing but old sheets. They work and they cost you nothing.
Sheet covers plants by trapping an insulating layer of air. The fabric creates a barrier between cold air and tender leaves. Heat rising from the soil gets trapped under the sheet. Your plants stay warmer than the surrounding air all night long.
Use dry sheets for best results with cotton frost cover protection. Wet fabric conducts cold rather than blocking it. I made this mistake once when dew soaked my covers before temps dropped. The wet sheets actually made frost damage worse.
Now I store my sheets indoors and bring them out right before covering plants. Dry fabric insulates well. Wet fabric does the opposite. Check your sheets if morning dew has been heavy and switch to dry backups.
Securing edges to the ground is the real secret of fabric frost protection. Loose sheets let cold air sneak under and defeat the whole purpose. I weigh down edges with rocks bricks or shovel some soil onto them. This traps warm air rising from the ground.
That trapped radiant heat does most of the protecting. Your soil stores warmth from your afternoon sun. The sheet keeps that heat close to your plants. It stops warmth from escaping into the cold night sky.
Old cotton sheets work better than new synthetic ones for you. Cotton breathes well and insulates even when slightly damp. Synthetic sheets trap too much moisture for your plants. I tested both and cotton always wins.
A two dollar sheet can save your fifty dollar plant. Check your labels for cotton content. Fitted sheets work great for your individual plants since the elastic helps hold them. Flat sheets work better for your rows.
For extra cold nights double layer your sheets or add a blanket on top. I combine a sheet with an old quilt when temps drop below 28 degrees. The added layers provide more warmth for your tender plants.
Take off your covers by mid-morning so your plants get sunlight and fresh air. Leaving covers on too long causes weak yellow growth. I pull mine off by 9 AM and fold them for the next cold night.
Read the full article: Protecting Plants from Frost That Works
