Okay, so you’ve got lettuce in the ground and frost is coming. What do you do? Don’t panic—I’ve got you. First, water the soil well the day before the frost. Wet soil holds heat better than dry soil, so it acts like a warm bath for your plants’ roots. Yes, it sounds counterintuitive, but trust me.
Next, cover your lettuce with frost cloth, an old bedsheet, or even a plastic cloche (but remove it during the day to let air circulate). The cover traps the earth’s heat and keeps the frost off the leaves. Don’t use plastic directly on the leaves—it can trap moisture and make things worse.
Does Lettuce Need Protection from Frost? | Gardener’s Path
And here’s a weird tip from my own experience: if you live in a windy area, anchor your covers with rocks or bricks. I once watched a perfectly good sheet fly away at 3 AM, leaving my lettuce exposed. That morning was heartbreaking.
