This paper describes the architectural and engineering features, operating procedures, and history of the planning and financing of the Southeastern Plant Environment Laboratories (SEPEL). The controlled environment laboratories that form SEPEL consist of two units, one at North Carolina State University, the other at Duke University. Together, this two-unit phytotron includes nine temperature-controlled greenhouses and over 100 plant growth chambers with a total floor space of over 8000 square feet as well as several laboratories with special equipment.