The following article offers some guidance on how to collect, preserve and store these seeds.
Collect your heirloom seeds after the morning dew has dried preferably on a dry and sunny day. This usually occurs around 10:00 a.m. Make sure that your herbs, fruits, and vegetables are completely dry.
Always save more seed than you think you may need and save equal amounts of seed from each healthy plant. Saving seeds from each plant ensures that all the traits of the type of herbs/fruits/vegetables are preserved and saving equal amounts of seed from each plant ensures that the original balance and range of traits is preserved.
Fruits that have seeds in their pulp are best picked when the fruit is fully ripe and turning soft (but not rotting). These include tomatoes, eggplants, melons, chillies, and passion fruit. However, some fruits are best picked when the seeds have had time to plump up, that is, just after maturity. These include red and green peppers, butternut, gem squash, pumpkin, and marrows. Some fruit seeds need to fully mature before being harvested. This excludes a further 3 weeks before the seeds are ready to be picked. These include cucumbers, zucchinis, okra, and sweet corn.
Broad beans, runner beans, bush beans and maize should completely dry out on the plant before being harvested. If rain is forecasted, the seed heads and pods should be removed and placed in a well-ventilated, dry area until the seeds are hard.
Note that some plants scatter their seeds as they mature. These include, carrots, parsnips, lettuce, onions, and celery. As these seed heads approach maturity, they should be placed into paper bags and shaken daily, that way the released seed falls into the bags rather than on the soil.
How to clean Heirloom Seeds?
Plants that scatter their seeds do not require need any attention. They are clean and dry and just need to be harvested and stored. However, some seeds are fleshy, that is, they surrounded by pulp that requires removal. For example, with tomatoes you would need to scoop out the flesh with a spoon and place it in a bowl of water. Subsequently, you would need to separate the flesh and seeds by rubbing the flesh vigorously with your thumb and forefinger. Finally, you would drain the water through a sieve to catch the seeds and allow them to completely dry out on a plate (±10 days).
The genetic material of heirloom seeds can still change or be lost in storage even after proper collection and sanitation. Seeds may die if they are stored for too long or if they are stored under unfavourable storage conditions.
The viability of heirloom seeds preserves their integrity. Some seeds remain viable for a long period. For example, peas, beans, cabbage, cauliflower, and brussels sprouts last for at least 3 years, while tomatoes squash, cucumber, and melon lasts 5 years or longer. However, other seeds are only viable for a short period. For example, corn, onion, leek, parsnip, and salsify only last for one season.
You can place harvested heirloom seeds in paper bags and store them in a dark pantry or cupboard. Keep in mind that the enemies of seeds are heat, light and humidity. In addition, label your seeds indicating their type and time of harvest. Alternatively, you could store them in dark glass jars or plastic. However, seed transpiration can cause moisture build up in these containers ultimately spoiling the seeds. Thus, when storing seeds in these containers, you run the risk of your seeds going mouldy.
If you use glass or plastic, then a layer of silica gel must be placed at the bottom of each container and the gel should subsequently lined with paper towels. You may then fill your jars with your seeds. The silica gel will turn from its normal blue colour to pink when the seeds start to transpire. When this happens, you will have to remove the seeds, and replace the silica gel until your seeds need to be planted.
Saved heirloom seeds should be stored at a cool temperature (below 10°C/ 50°F). If you are unsure as to when you will plant your seeds again, you can store them in the fridge (in glass jars) at 5°C/41°F.
After following all these tips, a germination success rate of 50%-80% can be expected when you replant your seeds. Please note that this is also dependent on the type herbs, fruits, or vegetables you are growing, climatic conditions and soil viability.