A sunlight exposure indicator device is disclosed that can determine the amount of time (e.g., hours) of PAR sunlight that occurs in a specific area for the optimal growth of a plant, as corresponds to the plant industry common designations of Full Shade, Partial Shade, Partial Sun and Full Sun. These designations can be used to determine plant selection for all types of plants including grasses, shrubs, flowers, vegetables and herbs, and trees. This device utilizes irreversible, slow-reacting, photochromic pigments applied to a substrate. Using multiple instances of this device will allow someone to easily test and accurately determine the amount of PAR sunlight (hours) received during a one-day sunlight cycle in multiple spots simultaneously. The sunlight exposure indicator device is a one-time-use, non-electronic, disposable device.