Seeds are small packages of life containing the embryo of a new plant, along with everything it needs to germinate and begin life. Although they seem dead, seeds are only dormant, still alive and breathing within their hard exterior coat. The best way to ensure seeds are viable and can be grown successfully in future generations is to store them well. Storing seeds well for good viability means ensuring they are dry and kept somewhere cool and dark (and with as consistent a temperature as possible, a bit like storing wine). Seeds that are subjected to high temperatures or high moisture will lose viability much more quickly than expected. Stored well, most vegetable and herb seeds should have a basic viability of between 2 and 5 years.
How to Store Seeds
1. Ensure seeds are dry before storage
Seeds must be thoroughly dry before storage to ensure that they don’t mould or rot and that they don’t start the germination process while in storage. Thorough drying of seeds will help them to stay safely dormant until moisture and warmth are deliberately applied for germination. Smaller seeds dry more quickly than larger ones. You can tell if larger seeds such as peas and beans are dry enough if the outer coat doesn’t crack or indent when you try to bite into it. If the outer coat is still soft enough to bite into, the seeds are not dry enough to store!
For dry processed seeds (like legumes, herbs, leafy greens), wait for as long as you can for seeds to mature and dry out on the plant as much as possible, and then harvest them with their pods or flower heads intact. For beans, freeze to kill bean beetle; for other smaller seeds, consider hot water treatment if needed*. Spread out pods/stems/flowerheads on a screen (a flyscreen is great) or tray with newspaper, paper towel or tea towel to stop moisture building up on the tray and leave somewhere cool, dark with some airflow and wait. Seed stems and heads can also be placed in a paper bag or hessian sack and hung somewhere in the breeze. Air circulation is key. In both cases, simply wait a week (for smaller seeds) or two (for larger seeds), clean seeds and they should be dry. Different climates and seasons will make drying seeds easier or harder. If the weather is particularly humid, seeds may need longer to dry and may need a slight breeze to ensure they don’t start to mould. If in doubt, leave seeds to keep drying for a bit longer before storing. It is not safe to dry seeds in the oven, time and air circulation will do the trick.
*Check out the section on processing seeds to learn more about freezing beans and heat treating other seeds to protect seeds and help stop spread of pests and diseases.
For wet processed seeds, like tomatoes or eggplant, process according to your preferred method (see the section on wet processing seeds) and then spread clean seeds out on a tea towel or a fine screen. If your weather is particularly dry, you can spread out on baking paper. Make sure the seeds are as separated from each other as possible to allow air circulation and also to make it easier to separate them once dry. Leave to dry in a cool, dark place with some airflow for a couple of weeks.
As an extra precaution, seeds can be kept in packets or jars with some oven dried rice which will help to wick any excess moisture away from the seeds. Simply spread rice on a tray and dry in a low oven until super crispy. Put a tablespoon full of rice in the bottom of each jar or packet and then put in seeds on top. Some rice will get mixed with seeds but it won’t matter. Or you might like to make mini packages of dried rice to place in each jar or packet to keep the rice and the seeds separate. Some seed savers also like to use mini packets of silica gel which will also wick moisture away from the seeds.
2. Storage containers and conditions
Once seeds are thoroughly dry, make sure the container or packet they will be stored in is also dry – and clean. Any type of container is fine for seed storage: glass or plastic jars, paper envelopes, plastic lunch bags. The key is to make sure that there will not be major fluctuations in temperature and humidity for the seeds. Paper bags or envelopes won’t trap the seeds in an airtight humid environment like glass jars can; but they will let in ambient humidity, a problem that you don’t get with airtight containers. In more humid climates, it might be best to store seeds in airtight containers making sure that they are very dry and contain a wicking agent like dry rice or silica gel.
Seeds should be stored in a dark place, certainly away from direct sunlight. Think about it as the seeds needing somewhere safe and quite and dark to sleep until they need to wake up and germinate. If you can, use opaque or dark coloured plastic or glass containers or keep in a dark drawer or cupboard.
Temperature fluctuations, particularly extremes of heat, can seriously impact the viability of stored seeds. If you can, store seeds in a cool cupboard or even a wine fridge at constant cool temperatures. A practical and free alternative is polystyrene boxes.
3. Labeling Seeds
Every long term, enthusiastic seed saver will have a ‘surprise tomato’ or ‘unknown pumpkin’ in their collection: the result of forgetting to label or losing labels that have been diligently transcribed. Even when you’re sure you won’t possibly forget the name of the seeds, or where they came from, or the date you harvested them, you will! When setting seeds aside to dry before storage, write out a label on a slip of paper (or even better, a sticker), that can’t be separated from the seeds while they are drying. When packing the seeds into their longer term storage, either write directly on the envelope container (watch out for markers being rubbed off glass and plastic over time) or on a sticker to attach to the container or on a piece of paper which is tucked into the container with the seeds.
You can include as much information as you want on a label but the bare necessities are: common and botanical names of the plant; date of seed harvest; and location where plant was grown (who’s garden and/or which part of your garden?). You might also like to include information like where the seed originated (did you buy it or was it a gift or a swap and who and where from, do they have a story about the seeds?), characteristics of the plant and the flowers/fruit (e.g. ‘flowered vigorously’, ‘most flowers set fruit’, ‘larger fruit than normal’); or notable points about the conditions or season the plant was grown in (‘next to north facing wall’, ‘very wet, cool summer’, ‘grown in pot’). You might like to get more specific and note exact flowering and fruiting dates, production per plant etc.
Labeling the seed container with this sort of more detailed information will help you remember and keep track of the conditions the seeds grew in and learn about how they are adapting. It might help you to decide when and how to plant them next time and it might be useful information for anyone you share seeds with. You might also like to record this information separately, cross-referencing to the particular container of seed through an indexing system. See the section below on Starting a Seed Library for some ideas about how to catalogue and reference your own or your group’s seed collection that will help you to keep track of the life of your seeds and the stories of the people who grow them.
Contributors: Lloyd Sharp (?)