A seed bank (also called seed banks, seeds bank, or seed vault) stores seeds to protect genetic diversity. This makes it a type of gene bank. There are several reasons to store seeds. One reason is to keep the genes that plant breeders use to improve crops, such as increasing food production, making plants more resistant to disease, helping plants survive dry conditions, improving nutrition, and enhancing flavor. Another reason is to prevent the loss of genetic diversity in rare or threatened plant species, which helps protect biodiversity outside their natural environment. Many plants that humans used long ago are now used less often; seed banks help preserve their historical and cultural importance. Seeds stored in seed banks are kept at very low temperatures and low moisture levels to protect them from loss. This is especially important because other ways of keeping seeds, like in natural habitats or field collections, can be harmed by natural disasters, disease, or war. Seed banks are sometimes called seed libraries because they hold valuable information about how plants have adapted to stress. These seeds can also be used to create new types of seeds with specific traits. The work of seed banks often lasts for many years or even hundreds of years. Most seed banks are supported by public funds, and their seeds are usually available for research that helps the public.

Storage conditions and regeneration

Seeds are living plants, and keeping them healthy for a long time requires controlling the amount of moisture and temperature during storage. As seeds grow on the parent plant, many develop a natural ability to survive drying. These seeds, called "orthodox" seeds, can live longer if stored in a dry, cold environment. How dry or cold the storage should be depends on how long the seeds need to be kept and how much money is available to build storage facilities. In the 1950s and 1960s, a scientist named James Harrington created simple rules for seed storage, known as "Thumb Rules." One rule, the "Hundreds Rule," states that the total of the relative humidity and temperature (measured in Fahrenheit) should be less than 100 for seeds to survive five years. Another rule says that reducing the water content by 1% or lowering the temperature by 10 °F (5.6 °C) can double the time seeds stay alive. Studies in the 1990s showed that drying or cooling seeds too much can stop being helpful, so these steps should not be overused.

To help seeds last longer, the Food and Agriculture division of the United Nations and an organization called Bioversity International created guidelines for seed banks worldwide. These guidelines suggest drying seeds to about 20% relative humidity, placing them in high-quality, moisture-proof containers, and storing them at −20 °C (−4 °F). These conditions are called "conventional" storage methods. Seeds from important crops, such as corn, wheat, rice, soybean, pea, tomato, broccoli, melon, sunflower, and others, are stored this way. However, some seeds from plants like citrus fruits, coffee, avocado, cocoa, coconut, papaya, oak, walnut, and willow cannot survive the dry, cold conditions of conventional storage. These seeds must be stored using very cold temperatures, a method called cryogenic storage.

Over time, seeds slowly lose their ability to grow. It is difficult to know exactly when this happens, so trusted seed banks regularly check how well seeds can germinate during storage. If the germination rate drops below a certain level, the seeds must be planted again, and fresh seeds must be collected for future storage.

Some seed banks may use simpler methods if their goal is to keep seeds available year after year and reduce costs for farmers in a specific area.

Challenges

One of the most important challenges for seed banks is choosing which seeds to collect. The collections must be useful and provide genetic diversity that people can access. They also must avoid collecting seeds that are already in other collections.

Keeping seeds alive for many years is another major challenge. Orthodox seeds can be stored using standard methods, but many other seed types require special storage techniques. These techniques are improving quickly, but some areas may not have the tools or resources needed.

Some seeds cannot be stored for long and must be regrown by planting them to create new seeds. A study by Parzies and others in 2000 showed that this process can reduce the number of different genetic traits in seed populations. This finding has led seed banks worldwide to carefully examine their methods. Regrowing seeds is now understood to not always protect all genetic diversity perfectly.

Alternatives

In-situ conservation of seed-producing plants is a method used to protect these plants in their natural environments. This includes creating National Parks, National Forests, and National Wildlife Refuges to preserve the habitats of these plants. These areas allow plants to grow and change naturally over time through processes like natural selection. In-situ conservation for agricultural plants happens on farms where seeds are grown and protected.

An arboretum is a place where trees are planted and kept safe in a protected area.

A seed library, supported by a community, is a more affordable way to store and share local plant seeds.

It is well known that some seeds can stay hidden in the soil for a long time without growing (Hills and Morris 1992). However, there is not much information about how this happens in northern Ontario. More research is needed to learn which plant species are in the soil and how many seeds exist in different types of forests. This research would also help understand how these seeds help plants grow again after events like fires or storms. Tables showing seed numbers and types are provided for boreal and deciduous forests, and the research done so far is discussed. This review includes information about: (1) how seeds change over time in the soil, (2) how seeds function in the soil, (3) seed banks in boreal and deciduous forests, (4) how seed banks affect plant growth after disturbances, and (5) suggestions for starting seed bank studies in northern Ontario.

Longevity

Seeds can remain alive for hundreds or even thousands of years. The oldest seed that has been dated using a scientific method called carbon-14 dating and successfully grown into a plant was a Judean date palm seed about 2,000 years old. It was found during excavations at the palace of Herod the Great in Israel.

In February 2012, Russian scientists announced they had grown a narrow leaf campion (Silene stenophylla) from a seed that was 32,000 years old. The seed was discovered in a burrow 124 feet (38 m) deep in Siberian permafrost, along with 800,000 other seeds. Scientists placed the seed tissue in test tubes to grow it until it could be moved to soil. This shows that DNA can stay intact for very long periods under the right conditions.

Climate change

As climate change continues, seed banks may become more important for conservation. Seed banks provide communities with seeds that can survive changing weather conditions. When challenges from climate change occur, seed banks run by local communities can help people access a variety of crops that grow well in their area. These banks also support traditional knowledge about managing plants, including how to choose, care for, store, and share seeds.

Facilities

There are about 6 million seed samples stored in about 1,300 genebanks worldwide as of 2006. This number is a small part of the world's total biodiversity, and many areas have not been fully studied.

• The Svalbard Global Seed Vault is built inside a sandstone mountain in a man-made tunnel on the frozen Norwegian island of Spitsbergen, part of the Svalbard archipelago, about 1,307 kilometers (812 miles) from the North Pole. It is designed to survive major disasters, such as nuclear war or world war. It is managed by the Global Crop Diversity Trust. The area’s permafrost keeps the vault below freezing, and the seeds are protected by 1-meter thick walls of steel-reinforced concrete. The vault has two airlocks and two blast-proof doors. It accepted its first seeds on February 26, 2008.

• The Millennium Seed Bank is located at Wakehurst Place in West Sussex, near London, UK. It was established in 1996 and is the largest seed bank in the world. It will eventually be at least 100 times larger than the Svalbard Global Seed Vault. It stores billions of seed samples in a nuclear bomb-proof underground vault. Its goal is to store seeds from every plant species possible. As of 2024, it holds over 2.4 billion seeds from more than 39,000 species. It also sends seeds to other locations worldwide, tests seeds every 10 years, and conducts research.

• The Institute of Plant Genetic Resource in Saint Petersburg, Russia, is likely the oldest and still one of the 5-6 largest seed banks in the world. It was started in 1924 by Russian geneticist Nikolai Vavilov. It survived the 28-month Siege of Leningrad during World War II because some botanists refused to eat the stored seeds and potatoes, even when starving. Some sources say it was founded earlier, in 1894, by Alexander Batalin.

• The Australian PlantBank is located in the Australian Botanic Gardens at Mount Annan, New South Wales. It is part of the Millennium Seed Bank Project and includes the former NSW Seedbank, created in 1986 to preserve native Australian plants, especially those at risk. The Australian Grains Genebank (AGG) in Horsham, Victoria, is a national center for storing plant genetic material for breeding and research. It works with the Australian Seed Bank Partnership on a project to collect wild relatives of crops. It opened in March 2014. The bank was created because of extreme summer temperatures, up to 40°C (104°F), which required year-round protection for the seeds. It aims to collect and conserve seeds from Australian wild crop species not well represented in other collections. The George Hulbert Seed Vault in Wagga Wagga, New South Wales, preserves rice varieties, including those from before the Green Revolution.

• The Indian Seed Vault is a secure seed bank located in a high-altitude mountain pass called Chang La in Ladakh, India. It was built in 2010 and is said to be the second largest in the world. The BBA (Beej Bachao Andolan — Save the Seeds movement) began in the late 1980s in Uttarakhand, India, led by Vijay Jardhari. Seed banks were created to store native seed varieties.

• The National Center for Genetic Resources Preservation in Fort Collins, Colorado, is the largest seed bank in the United States. The Desert Legume Program (DELEP) in Tucson, Arizona, focuses on wild legume plants from dry regions worldwide. DELEP has over 3,600 seed collections from nearly 1,400 species of legumes in 65 countries across six continents. These collections are also stored in the National Center for Genetic Resources Preservation and the Svalbard Global Seed Vault. DELEP is an accredited collection of the North American Plant Conservation Consortium.

• The National Gene Bank of Plants of Ukraine was created in the 1990s and is described as one of the largest seed banks in the world. It was damaged during the Russian invasion of Ukraine in 2022 but remained mostly intact.

• The INRAE Centre for Vegetable Germplasm in Avignon, France, stores over 10,000 species of five vegetable crops as seeds: eggplant, pepper, tomato, melon, and lettuce, along with their wild or cultivated relatives. These species come from diverse geographic regions and have detailed information about their traits and origins.

• Meise Botanical Garden in Belgium houses a seed bank that preserves endangered and rare wild plants from Belgium. It also stores seeds from wild beans, wild bananas, and Copper plants of Katanga.

Seed banks classification

Seed banks can be grouped into three main categories: assistentialist, productivist, and preservationist. In practice, many seed banks use a mix of these categories, and their goals may vary based on their purpose and the needs of the area they serve.

• Assistentialist seed banks: These seed banks focus on helping local communities and small farmers. They provide seeds that grow well in local areas and are easy to care for. They choose seeds that produce high yields, resist pests and diseases, and require few resources like water or fertilizer.

• Productivist seed banks: These seed banks focus on supporting large farms and businesses. They provide seeds that produce high yields, resist pests and diseases, and require few resources. They prioritize seeds that are suitable for large-scale farming and can be grown in large amounts using machines.

• Preservationist seed banks: These seed banks focus on protecting the variety of wild and farmed plant species. They work to save the genetic diversity of plants and make seeds available for research and breeding. They choose seeds that are rare, endangered, or have special genetic traits.

Early concepts

In Zoroastrian mythology, Ahura Mazda told Yima, a famous king from ancient Persia, to build an underground place called a Vara. This structure was meant to hold two seeds from every type of plant known at the time. The seeds had to come from plants without any problems, and the Vara had to be strong enough to survive a 300-year long, harsh winter. Some scholars believe a similar story exists in Norse mythology, where an underground garden called Odainsaker was created to survive the three-year fimbul winter before Ragnarok. This garden was meant to protect people and plants that would help restart life after this event.