Completing my seed order this year made me think: I’ve got to find time to save more seed of more plants this summer and fall; and I’ve got to do a better job of storing any seed, purchased or saved from the garden, so that it retains its viability as long as possible.

Not that I’m not getting great value from the seed I order. Less than $4 worth of pole bean seeds should produce more than 150 pounds of beans. That’s a good pile of beans.

But ordering more than a few of those $2, $3 and $4 packets of various seeds adds up quickly (although the total is still less than a weekly trip to the grocery store for an average family).

Seed of non-hybrid tomatoes, for example, can be saved fairly easily. These plants are largely self-pollinating, so saved seed should generally produce the same variety of fruit. You can just scoop some seeds out of a ripe tomato, plop them on a piece of newspaper, and let them dry. One gardener I know does this, not bothering to separate the seed from its surrounding gel. After the gel and seed dry, he stores it, and the following spring just breaks the seed apart to plant it.

You can ferment tomatoes to extract seed and eliminate most of the gel. Just cut up some ripe tomatoes, put them in a container of water and let them sit for four days or so, until a mass of frothy goop forms on the surface of the water. Pour this froth off, then strain the remaining water and tomato seeds through a tea strainer, rinsing and straining the seeds a few times until they’re clean enough for your standards. Then plop the seeds onto a newspaper or paper towel, spread them out so that they’re one seed layer deep, and let them dry.

Beans can mature and the pods can dry on the vine; or, if it’s late in the season and the pods aren’t quite dry yet, bring the vines indoors to dry. Hang them upside down in a greenhouse, garage or porch, for example, until they’re dry. Once the pods are brittle, you can put the vines on a tarp or in a grain bag and beat them or stomp them to break the pods open. I heard one gardener suggest putting the filled grain bag under your truck tire and driving back and forth over it. Becky Sideman, a professor of horticulture at the University of New Hampshire, says she cuts a small hole in the bottom of the grain bag after beating it, and the beans fall out the hole, leaving most of the chaff behind.

With other plants with dry seeds, including flowers such as echinacea and calendula, you can simply hang the mature, spent flower heads upside down, place a paper bag around them, and collect the seeds as they mature. (Of course, these two plants also self-seed in the garden.)

Whether you save seeds from the garden or from seed companies, proper storage — i.e., cool and dry — is the key to making it last as long as possible. A rule of thumb is to have the relative humidity plus the temperature (F) add to less than 100. If you just store seeds indoors in paper packets, it’s easy to exceed 100 when, for example, the temperature in the house is 70 F and the humidity is 40 percent.

A good way to store seeds is to put them in an airtight glass jar with some silica gel and keep the jar in the refrigerator. The gel absorbs moisture, keeping the humidity in the jar at 5 percent. Fedco Seeds (fedcoseeds.com) sells beads of reusable silica gel for this purpose.

Although I had heard in the past that seeds will last longest if stored in a freezer, Jodi Lew-Smith of High Mowing Organic Seeds in Vermont said that this is not necessary when she spoke at the Farmer to Farmer Conference last fall. The danger with freezing containers of seeds is that condensation that occurs when you remove them from the freezer can moisten the seeds and reduce their storage life.

For more about saving and storing seeds, see Suzanne Ashworth’s book “Seed to Seed: Seed Saving and Growing Techniques for Vegetable Gardeners.”

To share seeds that you’ve saved and, possibly, pick up some other interesting seeds (and scionwood for fruit-tree grafting) that others have saved, come to the Seed Swap and Scion Exchange at the Maine Organic Farmers and Gardeners Association’s Common Ground Education Center in Unity on March 27 from noon to 4 p.m.