Many cannabis cultivators have been keen on the use of white or silver reflective plastic mulches for indoor cultivation. Many cultivators claim that it improves yields because of the increased amount of light caused by the reflectivity of the plastic. There has been a fair amount of research on other crops with reflective mulches but there is a lack of scientific research for cannabis. The objective of this study was to determine the effect of three types of plastic (black, white, and silver) on yield and cannabinoid concentration of day-neutral cannabis. The experiment was conducted in a glass greenhouse at Cornell University with supplemental high pressure sodium lights. There were three replicate blocks, each consisting of three plastic treatments and within each containing at least 3 replicate plants of the cultivar Dr. Chunk, 3 replicate plants of the cultivar Maverick, and at least 1 replicate plant of the cultivar Purple Star. The silver plastic treatment had the highest percentage of reflected supplemental light in the treatment sections. The black treatment sections had the highest average PAR in the treatment sections. There was no significant difference across any of the treatment sections for cannabinoid content percentages. The higher PAR average in the treatment sections may have contributed to the cultivars in those treatment sections being taller on average and having higher dry flower yields in the Maverick and Purple Star cultivars.