Plant Patents: http://www.uspto.gov/web/offices/pac/plant/
It states that:
"A plant patent is granted by the Government to an inventor (or the inventor's heirs or assigns) who has invented or discovered and asexually reproduced a distinct and new variety of plant, other than a tuber propagated plant or a plant found in an uncultivated state. The grant, which lasts for 20 years from the date of filing the application, protects the inventor's right to exclude others from asexually reproducing, selling, or using the plant so reproduced."


One of the best tasting pluots that consistently is in the top ten for several years will soon be patent free in the USA:

Flavor King Plant Patent Information
http://www.freepatentsonline.com/PP08026.html

Flavor King's patent was filed on: 06/10/1991
So it will expire on 06/10/2011. That is less than 3 years!