I've just put in Serpette Guilotteau peas, on the windowsill, and All the Year Round lettuce, and Spanish Black carrots, under cloches.
All the Year Round is mentioned in Christopher Stocks' 'Forgotten Fruits', which is mainly about vegetables despite the name. It was around before 1856, and it's a selection from an 18th Century variety, Tennis Ball. This used to be pickled in brine. I've heard of pickled cabbage, but never of pickled lettuce!