A couple of months ago I did an experiment to see if I could get a jump on the season by sprouting lettuce under glass jars. As you can see from the picture above, the lettuce that I planted at the normal time without jars did much better. Oh well.
All is not lost!
Mid-March I planted some swiss chard and let it sprout the normal way. But then I covered a few of the seedlings with glass jars. Much better!