Handling and storing seed

After collecting seed and other attached plant material, we:

  • Store it for about 10 days in open trays, in the shade, at summertime room temperature. The aim is to dry the plant samples slowly so that seeds which are not fully mature have a chance to ripen. We leave all seed heads, stems etc that we have collected intact at this stage
  • We remove any insect pests (e.g. weevils) that may damage seeds as we see them. You can use a pooter to do this
  • The pods of some species like vetches and Bird’s-foot Trefoil throw their seeds when they dry out. We therefore dry these in containers covered in fine netting (e.g. net curtain)
  • After 10 days we move the seeds into a warmer location to dry them more thoroughly. The aim is to get seed down to under 50% relative humidity
  • For most species we then do some processing to get a purer sample of seed. For us the aims are to:
    • reduce the bulk to make storage easier
    • remove any bits of plant that might block a seed drill
    • remove lightweight material that may stop the seed flowing well in a seed drill
    • get a more pure sample that allows us to make an estimate of the weight of actual seed present
  • The processing varies greatly between species:
    • We may do no processing for species where the seeds break off flower heads easily when ripe (e.g. Small Scabious) as the sample is virtually pure seed anyway
    • Other species require more work. The plant samples are dry and hard so they can be spiky and produce dust when handled. We therefore wear a dusk mask and often gloves too
    • Cut off pods or seed heads may need breaking up first. We mostly do this by rubbing the sample against a large homemade sieve made with 6mm mesh (see picture). This is strong enough to allow us to use pressure to knock out seeds or break up seed heads of species like Cowslip and Common Knapweed. The mesh also separates out large pieces of stem etc
    • The next step is often sieving through various mesh sizes of garden or kitchen sieve to separate out the larger bits of stem, leaf and flower head. The homemade 6mm sieve is a useful start. Once the seed is separated from the plant, progressively finer sieves can be used to purify the sample
    • We often then sieve or pour the sample between two containers (large bowls or trays) in a steady breeze to get dust and small particles out of the sample (winnowing)
    • The seed sample is weighed then stored in lightweight cotton bags in a cool, shaded, dry location (we use cotton bags as these allow air circulation)
    • At all stages we keep all the plant material taken out during processing. This will contain some seeds, so we spread it by hand on the new grassland site after the area has been sown with the seed mix
    • The Millenium Seed Bank Project website includes the Seed Information Database (see below as well) This gives information about the storage behaviour of the seeds of many species. The process described above is suitable for seeds that have ‘orthodox behaviour’, which includes everything we collect apart from Pyramidal Orchid. This is different in that it can lose viability rapidly if dried
  • The Millennium Seed Bank Project information sheet ‘Post-harvest handling of seed collections’ describes in more detail how to get field collections of seed into the right condition for storage

(Seed information in ePIC – read more…) The Electronic Plant Information Centre is found on the Millennium Seed Bank Project website under Kew’s Science/Scientific databases/Other resources/Electronic Plant Information Centre.To find seed information about a species in ePIC , in ‘Enter scientific plant name’ put the first part of the Latin name, e.g. Anacamptis; tick just ‘Species-level information’; click on ‘Search’. You can then open up any records found in ‘Seed Information’ and then ‘view seed information entry’ for the species you are interested in, e.g. Anacamptis pyramidalis for pyramidal orchid).

Sieves and storage bags
Sieves and storage bags