Plants naturally create their own seeds for reproduction. Such seeds are called heirloom or heritage seeds. Gardeners will often harvest seeds at the end of a season to use for planting the following season.
When two different varieties of a plant are crossed through manual pollination, the resulting seeds are called hybrid seeds. These designer seeds grow into plants that produce fruit with the best qualities of the two original plants.
Seed manufacturers develop seeds with superior qualities to grow larger fruits or make them resistant to insects and disease. Such manufacturers use genetic modifications to alter genes in the DNA, which is the plant's internal instructions for growth. The seeds produced from genetically modified seeds are engineered so that they will not reproduce. New seeds must be purchased from the manufacturer for each garden planting.
Heirloom plants need to be protected from the pollens of genetically modified seeds. Exercise protective measures if you have heirloom plants and your neighbor plants a garden with genetically modified seeds. Pollen from genetically modified plants will destroy the ability of the heirloom plant to reproduce.
Genetically modified seeds dominate the agriculture industry to the point that the U.S. Department of Agriculture now classifies heirloom or heritage seeds as "alternative crops."