Crops refer to groups of plants grown for consumption. Despite domestication over many years, these plants are not so far removed from their wild relatives that they could reproduce if brought together. Many crops are still grown in the areas they originated and gene flow between crops and wild relatives impacts the evolution of wild populations. Farmers can avoid reproduction between the different populations by timing their planting of crops so that crops are not flowering when wild relatives would be. Domesticated crops have been changed through artificial selection and genetic engineering. The genetic make up of many crops is different than that of its wild relatives, but the closer they grow to one another the more likely they are to share genes through pollen. Gene flow persists between crops and wild counterparts.