Orthodox seeds are seeds which will survive drying and/or freezing during ex-situ conservation. According to information from the U.S. Department of Agriculture, there is variation in the ability of orthodox seeds to withstand drying and storage, with some seeds being more sensitive than others. Thus some seeds are considered intermediate in their storage capability while others are fully orthodox. One notable example of a long-lived orthodox seed which survived accidental storage followed by controlled germination is the case of the 2,000-year-old Judean date palm (cultivar of Phoenix dactylifera) seed which successfully sprouted in 2005. This particular seed is reputed to be the oldest viable seed, but the upper survival time limit of properly stored seeds remains unknown.
- Walters, Chris; Towill, Leigh (2004). "Seeds and Pollen" (PDF). Agricultural Handbook Number 66 The Commercial Storage of Fruits, Vegetables, and Florist and Nursery Stocks. USDA-ARS, National Center for Genetic Resources Preservation Preservation of Plant Germplasm Research, Fort Collins, CO. Retrieved 2008-06-21.
- Hanson, Wendy (2008-06-13). "Date palm seed from Masada is the oldest to germinate". Los Angeles Times.
- Bonner, Franklin T. (April 2008). "Chapter 4 Storage of Seeds" (PDF). Woody Plant Seed Manual,USDA FS Agriculture Handbook 727. National Seed Laboratory, 5675 Riggins Mill Rd, Dry Branch, GA 31020. Retrieved 2008-06-21.