Before the era of seed catalogues and garden centers, seed saving was a cornerstone of farming in general and of home gardening in particular. What exactly is seed saving? It is simply letting some of your plants go to seed and then saving those seeds in order to plant next year's crop.
Seed Saving Today
Today, seed saving is mostly practiced as a tool of empowerment for home gardeners. Like home canning, knitting, and other back-to-the-land type skills, it is a step away from complete dependence on supermarkets and department stores. It also keeps alive some endangered varieties of plants. Some would even argue that home seed saving is one of the last lines of defense in terms of food safety. Should the international network of food transportation break down because of either terrorist acts or natural calamity, it will be those with seeds who will at least be able to grow their own food afterward.
But aside from the practicality of saving seeds from your garden, it is also a more intimate way to connect with your food. Thoreau wrote, "Though I do not believe that a plant will spring up where no seed has been, I have great faith in a seed. Convince me that you have a seed there, and I am prepared to expect wonders." When you save seed, you are increasing the sense of wonder in your garden.
Managing a Garden for Seed Saving
There are multiple ways to manage your garden to get the most out of seed saving. For some crops, like butternut squash, seed saving is as simple as harvesting a ripe specimen and saving the seeds instead of roasting and eating them. For other crops, like lettuce, you have to let the plant continue to grow past its most delicious stage in order to produce seed. For lettuce, this means letting the plant "bolt," i.e. grow a few feet tall all of sudden and then produce flowers, and then seeds. Therefore, you could simply choose one lettuce plant to be your "seed saver" plant.
Some people choose to plant a separate "seed saving garden" where all the plants will be allowed to grow to full maturity and ripeness. This is especially useful if you are saving seeds from a very specific plant variety, like an heirloom variety that you don't want cross-pollinated with another variety. In that case you would make sure that the specific variety is far enough away from other varieties in order not to cross-pollinate. Some even hand-pollinate to ensure purity. However, this is probably not practical for the average home gardener. You'll do fine to just let a few of your plants go to seed, and then process the seeds.
How to Save Seeds
There are two main types of seed saving depending on the type of plant, wet processing and dry processing. Wet Processing Very simply, when the fruit of the plant is fully ripe, separate the seeds from the flesh of the fruit, wash them, and air-dry them on a non-stick surface. During washing, any seeds that float can be discarded as this is usually a sign of a non-viable seed. Some fruits and vegetables in this category are squash and melons.
Some seeds, like tomato seeds, actually have to be fermented to become viable. For tomatoes, mush up the fruit (with seeds) and add to a quart jar filled 2/3 with water. Let this sit for about a week (it will be fermenting during this time), then rinse, dry, and store the seeds in an air-tight, dry, and sterile-as-possible location, where the temperature will remain cool.
You might have read in the Bible about threshing and winnowing. Well, when it comes to saving seed, those skills are just as valuable today as they were back then. Threshing is separating a seed from its coating, usually by beating it or whipping the dry plant on the ground. Winnowing is separating the seeds from the chaff, traditionally by enlisting the help of the wind. For some plants, this can all be achieved by hand, as with beans. With beans, simply crack open the dry pod and remove the seeds. Other dry-processed plants include broccoli, cabbage, carrots, most herbs, flowers, and grains. Storage is the same as for wet-processed seeds.
Other Plant Varieties
Of course, some plants are propagated by means other than seed planting. For instance, potatoes can be stored through the winter, then each eye can be cut out and planted. Most fruit trees are propagated through cuttings. The methods listed above are general principles of seed saving. There are excellent books and online resources which will provide further information about specific plants.