You should cover your vegetables for frost when temps drop below 32°F (0°C) for tender crops like tomatoes and peppers. Knowing when to cover vegetables for frost can save your harvest from damage on cold nights.
I check the weather forecast every afternoon during fall and spring. When I see temps dipping below 35°F (2°C), I head out before sunset to cover my tender plants. Frost protection timing matters because covers work best when put on while the ground still holds heat.
Frost and hard freeze are not the same thing and your crops react to each one. Frost happens at 32°F (0°C) and damages tender crops like basil and squash. A hard freeze hits at 28°F (-2°C) and can kill even some cold tolerant plants.
UNH Extension tested different covers and found clear results. Lightweight fabric covers add about 2 degrees of protection. Heavy weight covers or blankets can add 6-10 degrees and save plants from hard freezes that would kill them.
Covering garden for freeze events takes some planning ahead of time. Set up your hoops or stakes during the day so you can drape fabric over them fast. I keep my row covers rolled up at the end of beds so I can pull them over plants in just a few minutes.
When I first started protecting plants, I waited until the last minute and lost some peppers to a surprise frost. Now I cover earlier rather than later. An extra night under fabric does less harm than one night of frost damage to your plants.
Remove covers in the morning once temps rise above 40°F (4°C). Plants need sunlight and air flow during the day. Leaving covers on too long causes heat stress and can rot stems where fabric touches wet leaves in the garden.
Frost protection timing also depends on how clear the sky looks at night. Clear skies let heat escape faster than cloudy ones. A forecast of 34°F (1°C) on a clear night might mean frost on the ground while the same temp under clouds stays frost free.
Water your plants well before a frost is coming to your area. Wet soil holds more heat than dry soil and releases it slowly through the night. This simple step can add a degree or two of protection without any extra covering work on your part.
Last October I forgot to check the forecast and woke up to wilted basil plants. The temp hit 30°F (-1°C) while I slept and those tender leaves turned black. Since then I set a phone alert for frost warnings so I never miss covering day again.
Hardy crops like kale and spinach can take frost down to 25°F (-4°C) without covers. But you should still protect them when temps drop below 20°F (-7°C) or during long cold snaps. Even tough plants suffer when frozen solid for days at a time.
Your covered plants will thank you with extra weeks of harvest in the fall. Taking 15 minutes to cover before sunset is worth the effort. It can mean the gap between fresh food and buying from the store all winter.
Read the full article: Winter Vegetable Garden: Fresh Produce All Year
