Saving Vegetable Seeds: What You Need to Know

An open-pollinated plant is naturally pollinated (by animals or wind) and produces a new generation representative of parent plants. Such varieties breed true as long as the parent plants are isolated from cross-pollination with other varieties or closely related species.

The definition of an heirloom is a little more challenging to pinpoint. Typically, heirlooms are open-pollinated varieties that have been around for at least 50 years and often have origins in a particular region or climate. Some say heirlooms shouldn’t be commercially available, yet they’re gaining such popularity with home growers (because of legendary flavor and adaptation to regional growing conditions) that seed companies are offering increasingly larger selections each year.

Hybrids result when two specific varieties or cultivars are cross-pollinated, a process that can occur naturally and with human manipulation. Breeders have long known that hybridization is an efficient way to combine the best traits of different varieties into a single plant.

For example, the popular ‘Early Girl’ F1 (meaning Filia 1, or first generation offspring) was developed in France during the 1960s as an early maturing ketchup tomato. Inadvertently, this full-sized, exceptionally flavored tomato also became a hit in the commercial home gardening market. Varieties have since been created to resist Fusarium wilt and other diseases.

Despite some recent confusion that links hybrids with genetically modified plants, hybrids are good to have in your garden – and they have been for centuries. If you’re a bit of a mad scientist, you can create hybrids at home once you understand the basics of pollination and saving seeds. Just be aware, if you plant the seeds from hybrid offspring, the resulting plants will run the gamut of variability, and most will not resemble the parents.

Ease into your savings plan

If you’re planning on collecting seeds this year, start with species and varieties that offer the best chance of success. To be absolutely certain your seed will produce true-to-form offspring next year, you will want to isolate many of your plantings from others of the same species. However, species with “perfect” flowers – those that include both female and male (stigma and stamen) parts – are less likely to cross-pollinate with others in the same species and need not be grown in total isolation.

Tomatoes, beans, peas, peppers and lettuce all have perfect flowers and are good options when collecting seeds for the first time, particularly if you didn’t isolate spring plants. Of these, tomatoes are probably easiest.

Because the tomato pollen source is so close to where it needs to be for pollination, tomatoes rarely cross-
pollinate. Even though tomatoes self-pollinate for the most part, if you plan to save the seed, it’s best to separate varieties by at least 20 feet.

Choose firm, ripe tomatoes for your seed source. The easiest way to collect tomato seeds is to ferment them from the pulp. Scoop the seed-bearing gelatinous center of the fruit into a jar and cover with water. Cover the jar loosely with a lid (don’t screw it on or you might have a tomato-goo explosion on your hands) or several layers of cheesecloth held in place with rubber bands. Store it in a warm place for one to three days before pouring off the scum, bad seeds and tomato chunks. It will smell like a homebrew experiment, so don’t panic.

The viable tomato seeds sink to the bottom. Add more water and stir. Do this three times over the course of seven to 10 days, and you should have healthy seeds to dry for next year. Dry them on a plate or towel for several days before storing the seeds in an airtight container.

Floral perfection

Peppers, peas and beans also have perfect flowers, although they also have a slightly greater tendency to cross-pollinate through insect visitation. If you didn’t grow different cultivars next to each other, you can save seed with reasonable confidence that it’ll be the same variety next season. If you had all your peppers next to each other, the pollen might mingle; you will wind up with peppers of all kinds if you save the seed and grow them out next season.

To minimize the chance of cross-pollination, keep a handful of bean or pepper plants out of the reach of bees and other pollinators. I use a portable cold frame with pull-over netting.

Another option with all self-pollinating varieties – particularly with beans and peas – is to cover the plants with lightweight tulle netting. Drape it over your plants before the flowers open. You can also assist the pollination process by gently shaking the plants a couple of times a day to allow the pollen within the flower to reach the stigma, but it’s not absolutely necessary. Once fruit begins to set, remove the netting.

To save pepper seeds, allow the best-looking peppers to fully ripen. Pick the pepper, cut out the seeds and allow to dry completely on a paper towel or screen.

For beans and peas, leave the pods to dry completely as long as the weather permits. This is usually six weeks past when you would harvest them to eat. If a frost threatens, pull the entire plant up by the root and hang it upside down in a garage or storage shed to dry. To collect the seeds, pop open the pods and spread the seeds on a towel for a week to ensure they’re completely dry before storing them.

When saving seed from lettuce, bolting is a good thing. Each tiny white or yellow blossom will produce a single seed. After the lettuce has gone to seed, allow it to ripen a couple of weeks before harvesting. Shake the cluster to gather ripe seeds or cut the stalk and hang it upside down over paper to collect fallen seeds.

Imperfect but delightful

Other fruits and vegetables are more challenging because they don’t have perfect flowers; they have separate male and female flowers, which require insects or wind for pollination. This makes segregation imperative if you’re going to maintain pure strains.

Squash, pumpkins and cucumbers fall into this category. To make certain the offspring are true to the parent plant, any time during the season, cover several female flowers with a brown bag or tulle netting secured at the base to prevent bees from pollinating them.

The female flowers are easy to find – they have a swollen ovary (looks like a small squash or cucumber) at the base of the bloom, while the male flowers do not. Because you’re keeping the natural pollinators away, you need to hand-pollinate them. To do this, use a small, soft-bristled paintbrush to collect pollen (swirl the brush around the central, pollen-producing stamens) from the male flowers and deliver it to a female flower’s stigma (centrally located pollen-receiving structure) on the same plant. Mark the female flowers you segregated so you’ll know which fruit to harvest for next year’s seeds.

Winter squash and pumpkins should be left on the vine until after a light frost. To save seeds, cut the fruit open and scoop out the seeds. Pick out any squash “guts” and dry the seeds on a towel for at least a week (in dry conditions). You can tell these larger seeds are completely dry when you can easily break them in half.

If the squash aren’t quite ripe before a hard freeze, you can cut them off the vine, leaving part of the stem attached, and store them in a cool place for three to six weeks to finish maturing before collecting the seeds.

For summer squash and cucumbers, allow them to ripen past the edible stage because the seeds need to be fully developed. Toward the end of the season you can allow them to stay on the vine until they’re dead before harvesting.

Cucumbers need to be fermented like tomatoes. Follow the same techniques of scooping out the inside and soaking in water for several days. Dry the ones that consistently sink to the bottom on a plate or towel.

Alternating years

Biennial crops, such as carrots and parsnips, don’t form seeds until the second season, making this a perfect time to plan for next year’s seed collection.

For carrots, cut back the foliage to roughly 1 inch tall and mulch heavily. In the spring, the plants will send up flower stalks. Carrots have perfect flowers, but they need to be pollinated by insects.

The good news is not many home growers save their own carrot seed, making cross-pollination with another garden variety unlikely. Carrots will readily cross with wild Queen Anne’s Lace,  so if it is prevalent in your area you’ll need to isolate the carrot flower heads with a bag or netting and hand pollinate.

Once the seed head dries out, you can shake out the seeds or rub the head between your hands over a plate to collect the seeds. Allow them to dry further for a few days before storing.

As with carrots, leave parsnips in the ground through the winter after trimming back the leaves. Mulch well once again to make sure they survive the cold temperatures. Parsnips will form large seed heads the following year. Once they’re mature, cut them off and hang them upside down to dry with a collection plate underneath.

Saving seeds requires more effort throughout the season, but it’s the only way to ensure you’ll have your favorite varieties for the seasons to come.

Store the spoils

Once you’ve gone to all the trouble to save seeds, it’s important to store them correctly or they will quickly lose their viability. Place seeds in airtight containers – freezer bags or film canisters (if you can find them anymore) work well – and add a desiccant packet if possible.

Keep the seeds out of direct sunlight and in a relatively cool, consistent environment. Metal ammo cans, available at many military surplus stores, make excellent storage containers since they’re airtight and rodent proof. An empty coffee can will also work. Store them in a basement away from heat sources or in a root cellar, for best results.

Seed viability depends on how well the seeds are stored, as well as the variety. You can count on decent germination for two to four years after collection as long as they’re stored properly.

Amy Grisak is a garden writer who uses her home garden in Great Falls, Montana, as a testing ground to learn new and improved ways to grow all sorts of fruits and vegetables in the challenging Montana climate.