Hazelnuts come from a few of the 15 species of mainly bushy trees in the northern-hemisphere genus Corylus. Corylus avellana and C. maxima are native to temperate Eurasia and were widely exploited in prehistoric times for their nuts and rapidly produced shoots, which were used as walking sticks and a surface for marshy ground. A much taller tree, C. colurna, accounts for much of the production in the Black Sea region of Turkey. Another term for the nut is “filbert,” which in the United Kingdom is applied to the more elongated varieties, and which may come from St. Philibert’s Day in late August, when hazelnuts begin to ripen. The late Roman cookbook of Apicius called for hazelnuts in sauces for birds, boar, and mullet; they’re an alternative to almonds in Spanish picada and romesco sauces, and an ingredient in the spicy Egyptian spread called dukka and the Italian liqueur frangelico. Hazelnuts remain especially popular in Europe, where Turkey, Italy, and Spain are the main producers. In the United States, nearly all hazelnuts are produced in Oregon.