The practical utility of chlorophyll fluorescence to forestry applications is reviewed. Major subjects include a review of past applications, sampling protocols, important fluorescence features, and instrumentation. Applications including the study of various stress effects, seasonal effects, and comparative sun/shade leaf physiology are provided. Chlorophyll fluorescence has been used mainly in applied research, rather than directly in operational forestry, but work has begun in this area. Sampling protocols include the selection and treatment of samples before assessment, and control of environmental conditions during assessment. Instrumentation is evaluated based on accuracy, versatility, ease of operation, and cost. Chlorophyll fluorescence ranks high among stress detection tests in forestry applications, because it is rapid, reliable, non‐destructive, quantitative, diagnostic, and the physiological basis of the assessment is understood.