From April 1 to April 7 I hardened off some lettuce plants, some kale, cabbage, spinach and chives. I decided to plant them in the ground on Monday (picture 1), because I knew last night was going to be cold (28 degrees) and I wanted to give the plants a chance to adjust. It was definitely cold last night! This morning I discovered that the water in the watering can was still frozen! I checked on the plants this morning and all was well. The plants were protected nicely in the cold frame(picture 2). Lettuce can tolerate temperatures as low as 28 to 32 degrees, but the leaves will burn. Kale can withstand colder temps.
I started these plants indoors on March 5, but I am going to try sowing some seeds directly in the cold frame next week (April 15) - 6 weeks before the last expected frost.