Certainly it's easy enough to buy seed packets for just about anything you'd want to grow. But once you've got a garden up and running, you also have the option of using the seeds produced by your plants. Assuming you'll not be planting them right away, you'll need to know how to treat and store the seeds for the future.
Allow your plants to go to seed. You'll want to gather the seed heads or pods when they're dry if possible, so choose a day when it has not rained recently, and a time of day after the morning dew has disappeared. Be careful not to wait too long to where the pods break open, birds or other intruders eat the seeds, or damaging frost sets in.
Preparing Seeds for Storage
One of the main factors to keep in mind at each stage is that moisture is the mortal enemy of seeds. You want to dry them, and you want to store them in a way that keeps them dry.
(There are drying-intolerant seeds that will not respond well to being dried out like this, but they are a very small percentage of what most gardeners would be growing-mostly seeds from certain trees, like acorns and buckeyes, as well as seeds from aquatic plants-but these are also the kinds of seeds that usually are not storable in the first place and tend to germinate shortly after falling to the ground.)
Place the seed heads or pods on racks or large sheets of paper. Allow them to further dry by leaving them in the sun or in a warm dry indoor area for several days to a week.
Separate the seeds from the dried seed heads or pods by shaking them or rubbing them with a gloved hand. Sift out the seeds from any other plant material or debris.
Place the seeds in a paper envelope. Written on the outside of the envelope should be the type of seeds they are, and the date. Don't wait to write this down, or it's easy to forget or get confused. As you gather seeds from different plants, put them into separate, clearly marked envelopes.
To protect from moisture, but also to protect from insects and rodents, your envelopes of seeds should be enclosed in a container such as a tin can with a lid, or a sealed mason jar.
When you've opened a box of anything that would be damaged by moisture, such as electronics or computer parts, you probably have seen the little packet of desiccant (with a warning that it is not edible). This is a substance that from within its porous container will soak up moisture from the air.
It's not a bad idea to include a substance like this within your container of seeds. To create a homemade desiccant, pour a tablespoon of powdered milk into the center of a facial tissue, fold up the tissue around it into a little packet, and set it on the bottom of the container of seeds. If you keep the seeds for a long time before using them, change the desiccant once every three months or so.
Germination is encouraged by heat, moisture, and light. So keep the container of seeds in a cool, dry, dark place-the back of the refrigerator, a corner of a chilly cellar, on a shelf in an unheated garage, etc. Opinion is mixed on the advisability of keeping seeds in a freezer, though some gardeners swear by the method.
The better your seeds are prepared and stored, the longer they will last. Almost all your properly stored seeds should be fine for the next planting season-say storing them over a few months of the winter and planting them in the spring-but even after a year or more a sizable number of properly stored seeds should germinate as they're supposed to when you finally plant them.