This week we are blanching the last of the Cos lettuce planted for the fall season. This upright form of lettuce is probably named for the isle of Kos in the Aegean Sea, between Greece and Turkey and is the most ancient form of lettuce.
Lettuce has been known and cultivated for at least 4,000 years and was likely first used as a sedative rather than as a salad ingredient. The lettuce genus, Lactuca, derives from the Latin lac, or milk, in reference to the milky sap called Lactucarium contained in the stems of wild lettuce. This compound is often known as lettuce opium and has long been used for its hypnotic and sleep-inducing properties.
By the first century CE varieties of lettuce that contained much less lactucarium and were much less bitter were available. Pliny the Elder described these lettuces as “possessed of cooling and refreshing properties” and recommended using them for “promoting the appetite.”
Lettuce was likely introduced to northern Europe and England by the Romans from whence it received the name of Roman or Romaine lettuce. Cos tends to be somewhat coarse with a slight bitterness, a holdover from its ancient ancestors. This can be remedied through whiting or blanching. The method we use was first explained by the Italian refugee Giacomo Castelvetro in 1614: “Our ingenious gardeners tie [the lettuce] tightly together round a cane, so that the insides blanch as white as snow and become wonderfully crisp.”
In a fortnight, or two weeks, the lettuce will head handsomely and the inner leaves will turn a creamy whitish color, which vastly improves the flavor and produces what the modern shopper would recognize as hearts of Romaine.