A seedbank stores seeds as a source for planting in case seed reserves elsewhere are destroyed. It is a type of gene bank. The seeds stored may be food crops, or those of rare species to protect biodiversity. The reasons for storing seeds may be varied. In the case of food crops: many useful plants that were developed over centuries are now no longer used for commercial agricultural production and are becoming rare. Storing seeds also guards against catastrophic events like natural disasters, outbreaks of disease, or war.
Orthodox seeds. These seeds have a natural dormancy feature, which allows for their long term storage with little damage to DNA, provided they are kept in a cool, dry environment. These seeds can remain viable for decades and are easily stored in seedbanks.
Recalcitrant seeds. These seeds cannot be stored at low humidity and subzero temperature without damaging the germplasm. They must be continuously replanted to replenish seed stocks. Some examples are the seeds of cocoa and rubber.
Optimal storage conditions
Seeds are dried to a moisture content of less than 6%. The seeds are then stored in freezers at -18°C or below. Because seed DNA degrades with time, the seeds need to be periodically replanted and fresh seeds collected for another round of long term storage.
Stored specimens have to be regularly replanted when they begin to lose viability.
Only a limited number of the world's biodiversity are stored.
It is impossible to store recalcitrant seeds.
Only 15% of all seedbanked plants are wild species; the remainder are crops.
There is a need for improvement of cataloging and data management. The documentation should include identity of the plant stored, location of the sampling, number of seeds stored and viability state. Other information, such as farming systems in which the crops were grown, or rotations they formed, should also be available to future farmers.
The financial cost of facilities are expensive for third world countries which contain the most biodiversity.
Seed banks may be accused of biopiracy.
In-situ conservation of seed producing plant species is another conservation strategy. In-situ conservation involves the creation of National Parks; National Forests; and National Wildlife Refuges as a way of preserving the natural habitat of the targeted seed producing organisms. In-situ conservation of agricultural resources is performed on-farm. This also allows the plants to continue to evolve with their environment through natural selection. An arboretum stores trees by planting them at a protected site.
Main article: Oldest viable seed
Seeds may be viable for hundreds and even thousands of years. The oldest carbon-14-dated seed that has grown into a viable plant was a Judean date palm seed about 2,000 years old, recovered from excavations at Herod the Great's palace in Israel. 
There are about 6 million accessions -- samples of a particular population -- stored as seeds in about 1,300 genebanks throughout the world as of 2006. This amount represents a small fraction of the world's biodiversity, and many regions of the world have not been bioprospected fully.
The Svalbard International Seed Vault will be built inside a mountain in a man made tunnel on the frozen Norwegian island of Spitsbergen. It will be designed to survive catastrophes such as nuclear war, hurricanes, and world war. It will be operated by the Global Crop Diversity Trust. A tunnel will be created in a sandstone mountain on Spitsbergen, which is part of the Svalbard archipelago, about 966 kilometers (600 miles) from the North Pole. The area's permafrost will keep the vault below the freezing point of water and the seeds will be protected by 1-metre thick walls of steel-reinforced concrete. There will be two airlocks and two blast-proof doors.
The Wellcome Trust Millennium Building (WTMB) houses the Millennium Seed Bank Project. It is located at Wakehurst Place in West Sussex. It provides space for the storage of thousands of seed samples in an underground vault.
Nikolai Vavilov (1887-1943) was a Russian geneticist and botanist who, through botanic-agronomic expeditions, collected seeds from all over the world. He set up one of the first seedbanks, in Leningrad (now St Petersburg), which survived the 28 month Siege of Leningrad in World War II. It is now known as the Vavilov Institute of Plant Industry.
Ellis, R. H., T.D. Hong and E.H. Roberts (1985). Handbook of Seed Technology for Genebanks Vol II: Compendium of Specific Germination Information and Test Recommendations. SGRP (System-Wide Genetic Resources Programme). Rome, Italy.
Engels, J. M. M. and L. Visser (editors) (2003). A Guide to Effective Management of Germplasm Collections. CGN, FAO, GRST, IPGRI, SGRP.
Kameswara Rao, N., J. Hanson, M. E. Dulloo, K. Ghosh, A. Nowell and M. Larinde (2006). Manual of Seed Handling in Genebanks. SGRP (System-Wide Genetic Resources Programme). Rome, Italy. 147 p.
Koo, B., Pardey, P. G., Wright, B. D., et al. (2004). Saving Seeds. CABI, IFPRI, IPGRI, SGRP.