Lettuce is known as a "cool season crop" because it thrives in cooler temperatures. If it's too warm, it fails to grow properly; it will be spindly and floppy and it may "bolt", meaning that it sends up a long stalk in order to go to seed. Lettuce will do this under one of two circumstances: either when it experiences repeated daytime temperatures above 72 degrees, or when it is nearing the end of its natural lifespan. If you are growing lettuce in your AeroGarden, place the Garden in an area of your home that does not regularly get warmer than 72 degrees.
Unfortunately, once lettuce has bolted, it will never be short, crisp and bright green again. Some people like to grow Salad Greens in the cooler months, and then a "warm season crop" like Chili Peppers or Cherry Tomatoes in the warmer months. Also, AeroGrow’s Romaine Seed Kit can withstand higher temperatures (up to about 76 degrees) without bolting.
