John Derbyshire eulogizes rhubarb, as well he might. I too fondly remember our patches in the Wyoming yard of my youth, dipping the ends in sugar. And rhubarb baked goods are noble things. But I was unaware of its historic renown:

Rhubarb has an interesting and exciting history. The Emperors of China used it as a diplomatic weapon, withholding exports of rhubarb to nations that had displeased them. See here:

The imperial commissioner Lin Zexu, who was sent to Canton in 1839 to put an end to the opium trade, wrote a letter to Queen Victoria pointing to the "fact" that the foreign barbarians surely would die if they could not obtain tea and rhubarb from China.