North American Fruit Explorers mailing list at ibiblio

["Doreen Howard" <gardendiva@charter.net>]

 It depends if the plant is sexually or asexually produced.  Either type of patent can be renewed for another term, too.

Doreen Howard

• Plant Variety Protection (PVP).  Used for sexually produced plants and seeds, especially open-pollinated ones and hybrids other than F1   generations.  A Certificate of Protection remains in effect for 18 years from the date of issuance.
• U.S. Plant Patent.  For new and distinct plants such as sports, mutants and hybrids that are asexually reproduced by tissue culture, grafting, budding, cuttings, layering or by division. Patent is good for 20 years from the date of application.