As agriculture became big business in the United States, the focus on plant hybrids caused a depletion in the variety of native, non-hybrid plants. About 25 years ago, some farmers became convinced that diversity and flavor were being sacrificed to the corporate need for uniform produce that was pretty, and at the same time, tough enough to stand transcontinental transport to the supermarket. They started saving and growing the old-fashioned, open-pollinated (without human intervention) seed varieties. These are now known as heirloom seeds, and their offspring are available in specialty produce stores and farmers markets.