Jiang and Ping represent one story of China and its farms. More than 90 percent of all farms in China are less than 2.5 acres, and the average farm size is among the smallest in the world.

Vertical Harvest is a 51,000-square-foot, vertical hydroponic indoor farm in downtown Westbrook. “We grow a variety of leafy greens here—everything from your head lettuce to your microgreens ...