U.S. Plant Patent Act of 1930
This law established patent rights for developers of new varieties of many asexually propagated plants, for example apple trees and rose bushes that are propagated by cutting pieces of the stem rather than by germinating seeds. Tuber-propagated plants, such as potatoes, were exempt from patent coverage because the part of the plant used for asexual propagation was also the part used as food. Similar laws were passed in Europe in subsequent years.

U.S. Plant Variety Protection Act of 1970
This law establish patent rights for developers of new varieties of seed-propagated plants, but not F1 hybrids. Carrots, celery, cucumbers, okra, peppers, and tomatoes were specifically exempted from patent protection. Under the farmers' exemption, farmers were allowed to save patented seeds for use on their own farms and could sell patented seeds to other farmers. Under the breeders' exemption, plant breeders could use patented plants to develop new patentable varieties. Several European countries already provided this protection with the establishment of the International Union for the Protection of New Varieties of Plants (UPOV) in 1961.

• 1980 amendment: carrots, celery, cucumbers, okra, peppers, and tomatoes were added to the list of patentable plants.
• 1994 amendment: F1 hybrids such as hybrid corn and tuber-propagated plants such as potatoes were added to the list of patentable plants. The farmers' exemption was restricted. Farmers are still allowed to save patented seeds for use on their own farms, but cannot sell patented seeds to other farmers. The breeders' exemption was restricted. Plant breeders cannot patent new varieties that are essentially derived from already patented varieties. These changes made U.S. patent laws similar to those in effect in Europe under the 1991 UPOV convention.

Utility Patents
The 1985 legal decision known as Ex Parte Hibberd (http://usitweb.shef.ac.uk/~zzc01ss/mable/mable2001/ v_bergner/Ex%20p%20Hibberd.htm) declared that utility patents, available to inventors since 1790, could be applied to plants. A utility patent is often sought for products related to genetic engineering because the utility patent can apply to the method used to engineer a plant, the genetic sequences that are inserted, and the plant that results. The Terminator patent is an example of a utility patent. It claims patent protection for the method used to make Terminator plants as well as the seeds and plants that are made. There is no exemption for farmers or plant breeders to use materials protected by a utility patent.