The tables at the bottom of this page show recommended storage times for some easy-to-save vegetables, herbs, salad plants, and flowers; seeds from closely related plants may have similar life-times. Seeds kept longer than these recommendations may not be viable, or not enough of the seed will be viable to make it worthwhile sowing them.
Parsnips and members of the onion family are particularly poor keepers, and must be sown the next season, whilst cucumbers and squashes keep surprisingly well, so it’s not generally true that “the smaller the seed, the longer it keeps”, although it is true that some very small seeds do keep for an amazing time.
If in doubt about whether to sow a seed that might not be in date, consider how much you value your time and effort against the value of the seed in question: persevering with an ‘heirloom’ variety is more worthwhile than a variety which is easy and/or cheap to obtain.
Self-saved seed should be mature, and be thoroughly dried in an open container, at room temperature (not by forced heating), for several weeks, before storing in air-tight containers, in a cool, dark environment. Seed exposed to damp, e.g. kept in an out-building in an unsealed container, will not keep for long, if at all. If your saved seed goes mouldy during storage, it was not dry enough, and may not be viable. Putting dry rice or silica gel in your seed container is one way of ensuring any residual moisture is safely absorbed.
Always label the seed container/envelope with the type, variety and date saved. Please do not bring seed to a seed swap if you have any doubts about its viability.
Remember to keep enough seed back for yourself, and only swap what you can spare: save more this season for sharing next time!
For more information on saving seeds, consult one of the excellent books on the subject:
The complete guide to saving seed – RHS ISBN 978-1603425742
Seedswap – The Gardener’s Guide to Saving and Swapping Seeds – Ivy Press ISBN 978-1908005564
Back Garden Seed Saving: Keeping Our Vegetable Heritage Alive – Eco-logic Books ISBN 978-1899233151
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|Herb||Keep Seed (Years)|
|Salad||Keep Seed (Years)|
|Flower||Keep Seed (Years)|