A number of factors are important for successful seed storage:
- dry seeds: the lower the humidity, the longer the seeds remain viable. Under no circumstances should seeds be placed in storage whilst damp, as they may then develop mould.
- airtight containers: when seeds have minimal contact with air they breathe less and age more slowly.
- cool conditions: temperatures between 0°C and 10°C are optimal. It is also important that the storage area is not subject to sudden temperature changes.
- darkened storage: seeds are best kept in a dark room or in an airtight container in a box away from light.
- dry storage: moist, warm conditions not only initiate germination, they promote the growth of harmful fungi and bacteria.
- mouseproofing: seeds must be kept safe from mice and other vermin. The most dangerous pests are flour moths, bean beetles and other insects, mice and rats.
- deep freezing is only possible if the seeds have been thoroughly dried, as otherwise they will be damaged. The seeds must be sealed into bags with a metallic lining. When maintained at –18°C they will retain adequate viability for 10 years, with some varieties lasting for 20 years.
- airtight containers such as resealable jam jars, bottles with airtight caps and glass jars with O-ring seals (Kilner jars) should be used. Preserve jars with wire closures have proved to be particularly suitable.
- Space can be saved by storing several seed packs in a large resealable container.
- Wooden boxes, nylon/plastic bags and cardboard boxes are unsuitable, as they are not sufficiently resistent to moisture and pests.