Annual seed saving at home
Seeds contain within them not only all the genetic instructions needed to produce a new plant, but also enough food reserves to get help the seedling germinate. With only a little effort they can be stored at home until the following spring.
The twin enemies of seed storage are warmth and water. Of the two, moisture is probably more important. A dry seed will last much longer at room temperature than a moist seed in the fridge. Try to keep seed as cool and dry as possible. You can keep them in a shed or greenhouse if you are only saving seed from one year to the next - just make sure that they do not become too hot or moist.
The way in which seeds are prepared for drying and storage depends very much on the crop. Some, like peas and beans, need no preparation other than shelling them and getting rid of the debris. Others, such as tomatoes, need special treatments. For a more detailed account you can refer to The Seed Savers Handbook by J. Cherfas, M. Fanton and J. Fanton (1996) or Seed to Seed by S. Ashworth (1991).
Water can make up between 10% and 15% of the weight of fresh seed. Getting rid of some of this moisture prolongs its life considerably. Heat, however, will destroy a seed, and seeds should never be exposed to temperatures greater than 35°C (95°F). Airing cupboards may be acceptable, but check with an accurate thermometer that the temperature never exceeds 35C.
One easy method of drying seed at home is to use a desiccant. Silica gel, dyed with cobalt chloride, is suitable. It is blue when dry and pink when wet, so it it is easy to assess its state. Damp (pink) silica gel can be dried by placing it in a very low oven 95°C (200°F) until it turns blue.
To store and dry your seeds you will need a large, airtight container, preferably with a wide mouth. A Kilner jar is ideal, but you can also use any glass jar with a homemade rubber gasket, which could be cut out of an old rubber tube, instead of the cardboard disc normally inside the lid. Place the seeds in paper envelopes or muslin bags. Don't use plastic or foil because they prevent moisture from leaving the seeds. Now weigh all the envelopes you plan to dry, and weigh out an equal quantity of dry (blue) silica gel. We find it easier to tie the silica gel into a bundle made from muslin, as it allows you to see the colour easily. Put the seed packets and silica gel into the jar and seal it. Place the jar in a cool place for eight to 12 days. By this time, small seeds such as tomatoes, lettuce, brassicas and so on, will probably be dry. Large seeds, such as peas and beans, take longer - about 12 to 16 days. The idea is to get them to below 8% moisture, a simple test is that if a seed breaks rather than bends, it is dry enough.
Getting ready to sow
When you want to remove seeds from storage you must allow the jar and its contents to come to room temperature before opening it. If you don't, water vapour in the air will condense out on the cold surfaces of the jar, and the wrapping material, ruining your efforts to keep the seeds dry. You should also allow the seeds to rest for a few days at room temperature and normal humidity before sowing them. They will slowly absorb water during this period and there is some evidence that allowing them to recover slowly is less damaging than putting them straight into moist soil.
- The Seed Savers Handbook by Jeremy Cherfas, Michael and Jude Fanton. (1996) Grover Books. ISBN 1-899233-01-6, £12.95
- Seed to Seed: Seed Saving Techniques for the Vegetable Gardener by Suzanne Ashworth (1991). ISBN 0-9613977-7-2, £15.95
To obtain Silica Gel, check out photographic shops and dried flower/art shop in your area.