vegetables even here in zone 6.  Although the temperatures at night frequently go below freezing, it is certainly possible to get lettuce and other cool weather crops to grow in October, November and even early December if you provide some covering.  I often have fresh lettuce and other greens for Thanksgiving.  The best time to start these plants is early September.  By the time late November rolls around you will have an entire crop of lettuce and other cool weather crops to put on the table.   Mizuna and other Asian greens perform particularly well in this cool weather.  You can even plant in containers to allow you to bring the plants inside if it get very cold.