Northern vigor is an effect seen in certain varieties of produce where varieties of plants grown in northern climates, then moved to southern climates, are hardier, better-producing, and better tasting.[1] This effect has been primarily observed in potatoes, but is also seen in strawberries[2] and garlic.[1][3] The Saskatchewan Seed Potato Growers Association has trademarked the term "Northern Vigour" for use with their potatoes,[1] but the effect is seen in produce grown throughout Canada and the northern United States.[3]
The exact cause of northern vigor is not known, but there are many theories. Some believe it has to do with the length of the days in northern latitudes,[1] or that it has to do with the combination of cold nights and hot days.[1] Others believe that the cold may kill off any disease that would otherwise affect plants from the south.[1] Still others think that the switch from a colder climate to a warm, less harsh environment makes it easier for the plants to thrive.[1] Researchers in Saskatchewan discovered that tubers raised in the cold and then moved to a warm environment undergo a series of physiological changes that may trigger more vigorous growth.[3]