Many modern vegetable varieties are specially bred as F1 hybrids. These seeds promise better uniformity and other desirable traits such as disease resistance. The new seeds of F1 hybrids can only be produced within a highly controlled environment, from two separate parent varieties that are kept isolated and then crossed – usually by hand. This makes them expensive and unsustainable. Hybrid plants increase farmers’ reliance on seed companies and therefore are subject to changes in prices and discontinuations. These varieties can also lead to a loss of diversity if open-pollinated varieties are not maintained. Additionally, hybrid seeds tend to be more expensive in comparison to open-pollinated varieties due to the maintenance of the two distinct inbred parent lines.