The smell of marijuana is rather strong and pungent and this is because of something called ‘terpenes’. These are a chemical compound present in marijuana plants which begin to kick-in at around the late-vegetative stage. Terpenes are the primary reason for the smell and generally, it is considered that the stronger the smell, the more potent the high will be. Terpenes have another major role to play - the smell repels away insects and pests who might otherwise affect the plants adversely.