Abstract Protected cultivation has been used to modify the microclimate to advance maturity, increase yields, and expand areas of production for many horticultural crops. Ancillary benefits of protected cultivation can include reduced numbers of pests and lower disease pressure. This discussion will limit the term “protected cultivation” to row covers, low tunnels, and individual plant shelters (“grow tubes”), addressing their applications in the production of small fruit. The foremost biological response of crops grown under protected cultivation is an increase in growth rate, induced primarily by elevated soil and air temperatures within the shelter and around the plant. The protected environment often has lower vapor pressure deficits between crop and atmosphere, resulting in less plant stress. Although many reports detail the biological responses of crops grown under protected cultivation, few include measurements of environmental variables within plant shelters. Understanding the physical principles ...