The Night Frost is Bad: Under 28 degrees.

Well I have a 5 day battle ahead. The temperatures at night are going to be in the mid 20's. The cups I put out last night... didn't do much. They are good for few degrees of protection, not 6 degrees or more. My cool weather crops were frozen through. That isn't so bad but for the up coming consecutive days. I have seen lettuce freeze through, and be fine. A lot of the cool weather plants have a different cell structure or mechanism. When they freeze the ice crystals don't typically rupture the cell membranes.

Looks like I will double insulate the plants. A 12 oz clear cup and a large black container will go over them.