It’s around 8:30 in the morning and I’m about to uncover the early lettuce. Floating row cover is a very lightweight spunbonded polyester, light enough not to crush seedlings when laid down directly on top. It lets in water and sunlight, and also retains heat, to differing degrees depending on weight. This one is medium weight, my all-purpose cover. It transmits 85% of sunlight and keeps the temperature 3-4°F warmer when the surrounding air is around zero. Over the last couple of nights, the greenhouse low was 19°F (-7°C)—the lettuce can take a little freezing, and would probably manage without cover. Still, every edge helps, and this one’s easy. Floating row cover is a common sight around here throughout the year, it’s my main organic alternative to pesticides (it keeps out certain flying insects on certain crops at certain critical times) and also gives you an edge in getting things out early and keeping them out late. Beat that frost!