Steady advancement over the past several decades in the optimization of controlled ecological life support systems (CELSS) design and performance has resulted in the development of a variety of approaches to CELSS control. This paper reflects this evolution by surveying the approaches used in controlling plant growth chambers currently in use in academia, industry, and government agencies. A table is presented summarizing the control system hardware and software used and the corresponding control laws implemented by these systems. The advantages seen by the science and engineering groups operating several plant growth systems are discussed. Troublesome or cumbersome properties of the control systems of some plant growth systems are also discussed as well as some of the solutions which have been derived or envisioned.