Perennial crops are a perennial plant species that are cultivated and live longer than two years without the need of being replanted each year.[1][2] Naturally perennial crops include many fruit and nut crops; some herbs and vegetables also qualify as perennial. Perennial crops have been cultivated for thousands of years; their cultivation differs from the mainstream annual agriculture because regular tilling is not required and this results in decreased soil erosion and increased soil health.[3] Some perennial plants that are not cultivated as perennial crops are tomatoes, whose vines can live for several years but often freeze and die in winters outside of temperate climates, and potatoes which can live for more than two years but are usually harvested yearly.[4][5] Despite making up 94% of plants on earth, perennials take up only 13% of global cropland.[4][6] In contrast, grain crops take up about 70% of global cropland and global caloric consumption and are largely annual plants.[7]
There is a growing movement to create perennial alternatives to annual crops particularly grains. From the 1920s to the 1950s, researchers in the former Soviet Union attempted to perennialize annual wheats by crossing them with perennial relatives such as intermediate wheatgrass. Interest waned when the crosses repeatedly resulted in sterile offspring, and seed yield decreased significantly. The next major time the project of perennializing grain was picked up was a wheat hybrid developed by the Montana Agricultural Experiment Station in 1986, which the Rodale Institute field tested.[8] For example, The Land Institute has bred a perennial wheat crop known as Kernza. By eliminating or greatly reducing the need for tillage, perennial cropping can reduce topsoil losses due to erosion,[9] increase biological carbon sequestration,[10] and greatly reduce waterway pollution through agricultural runoff due to less nitrogen input.