The pine nuts in your pesto come from one of several species of pinyon pine. The Mexican pinyon pine (piñonero) is Pinus cembroides Zucc., a species that forms dense stands in the dry, high plateaus of Mexico together with several species of oak, juniper, and agave. These stands are heavily exploited by local collectors for pine nuts that are later exported to the U.S. I took a group of graduate students from Columbia University to the pinyon pine forest shown above for several years as part of a tropical ecology class that I taught (thx, Patricia). The forest is located outside of Tepeyahualco in the Valley of Perote, Veracruz. One of the few forests that I have worked in that requires sunscreen. [NOTE: This is a wonderful habitat for inventory transects].