Walmart has taken an unspecified stake in Plenty, making it the first large retailer in the U.S. to make a significant investment in indoor vertical farming. Walmart will be represented on Plenty’s board. Plenty, which was founded in 2014, operates a vertical farm in South San Francisco and an indoor plant science center in Laramie, WY. The retailer will begin selling Plenty’s leafy greens in its stores later this year.