Seed developed from two varieties of parent plants which are genetically different but of the same species. Pollination resulting in a hybrid can occur either naturally or artificially. Commercially, the parents that are used to produce hybrids are usually inbred for specific characteristics. Gardeners must be mindful that hybrid plants cannot be counted on to produce plants with traits recognizable to the parent plant; traits will separate out in successive generations. Reputable seed stewards understand that seed work is slow work. The process of selecting for and stabilizing a desired trait to come true-to-type from saved seed takes a minimum of seven or eight years. However because of the high profits that are at play these days, there is a push to release new varieties as soon as possible, with the exact parentage of F1 hybrids remaining closely guarded trade secrets.

The word hybrid derives from the Latin word hybrida, which refers to the offspring of a domesticated sow and a wild boar. Besides not being able to count on seed being true-to-type, there is also the issue that on rare occasions, seed resulting from hybridization will be sterile (similar to when a horse and donkey mate to produce a sterile mule).