Aroma is produced by terpenes, volatile compounds concentrated in the resin glands of the flower. Different regular marijuana strains carry distinct terpene combinations, giving rise to scents described as citrus, pine, fuel, earth, or sweet fruit. Because unsexed lines vary between siblings, two plants from the same pack may smell noticeably different. Growers often keep a cutting of each female until harvest so that the most appealing one can be preserved.