Tallest one I've ever seen, about 7' tall.
~5 feet tall
Lactuca canadensis is a species of wild lettuce known by the common names Canada lettuce, Canada wild lettuce, tall lettuce, and Florida blue lettuce. Its true native range is not clear, but it is considered to be a native of parts of North America. It can be found in other parts, and on other continents, as an introduced species.