Kew Gardens' millennium seed bank

Kew millenium seed bank at Wakehurst Place, Sussex. Seed collections arrive by courier from around the world Photograph: Martin Argles/Guardian

The largest seed in the collection is the coco de mer seed and the smallest is a Chilean orchid – there are about 1m seeds in the vial Photograph: Martin Argles/Guardian

Seed pod of devils claw plant. The species of the seed collected needs to be checked at the herbarium (a collection of preserved plant specimens) Photograph: Martin Argles/Guardian

Seed pod of banksia plant. Usually several specimens are collected, and at least one stays in the seed bank's partner country Photograph: Martin Argles/Guardian

The seeds, together with pressed plant specimens and vital field data, are brought back to seed banks around the world for processing, research and long-term storage Photograph: Martin Argles/Guardian

Rota of seed collectors Photograph: Martin Argles/Guardian

Cleaning acer seeds. Once at the seed bank, seed is cleaned to reduce bulk and the risk of disease. This requires great care and expertise and to limit damage, much of the work is done by hand using sieves Photograph: Martin Argles/Guardian

Seeds in temperature cabinet, testing for viability. Most species have seeds that stay viable when dried to the low moisture levels necessary for long-term storage. However, certain species have seeds that are not tolerant to drying and cannot be conserved long-term in a seed bank. There are other ways to deal with these species Photograph: Martin Argles/Guardian

Cutting up seeds to test for viability Photograph: Martin Argles/Guardian

Seeds in humidity tests. Seed collections can be harmed by poor handling, and it is particularly important that they experience the correct temperature and humidity levels Photograph: Martin Argles/Guardian

Once the seed has been dried to the required level it is packaged and placed in the cold room where it is kept at a temperature of -20C Photograph: Martin Argles/Guardian

The length of time that each collection can be stored for is fixed by the biology of the seed. Depending on the species, seeds may live centuries – and even millennia Photograph: Martin Argles/Guardian

Eucalyptus virginii seed. The next phase of the seed bank project is an even more ambitious target of collecting a total of 25% - about 75,000 - of the world's plant species by 2020 Photograph: Martin Argles/Guardian