Seed collecting is fundamental to preserving plant biodiversity and food independence for future generations. The art of collecting, processing, and storing seeds has been practiced by cultures around the world for millennia. This ancient tradition does not require formal training as a botanist - rather an appreciation of the natural word and a curiosity to learn. Keep in mind that the more precise your pollination methods and record keeping, the more valuable your seeds are to other gardeners and farmers.
In selecting the plants from which to save seed, assess the condition of the whole plant, looking for disease and insect resistance, drought tolerance, vigor, color, earliness of fruiting, lateness of bolting, hardiness, uniformity, and trueness. You can influence your future crop characteristics by selecting seeds on the basis of size, shape, color, productivity, flavor, shelf life, and more. Although it is not guaranteed that the same characteristics will be expressed in the next generation, over time you will be able to influence the traits of your seed stock.
Harvesting of dry seeds must be done before winter rains set in, to prevent the seeds from molding in storage. In the event of an early hard frost warning, pull the plants out and hang them to continue drying for about a week, which allows the seeds to continue maturing fully. Many gardeners in seasonal climates harvest dry seeds into paper shopping bags for processing and cleaning during the winter months.
A variety of processing techniques are used, depending on the seeds' size, volume, and weight relative to the chaff. You can be creative and experiment with different techniques and equipment to suit your own circumstances.
The first method is called threshing, a process of beating or rubbing to separate the seeds from their containers. Brassicas, such as kale and cabbage seeds that are held in dry pods may be processed this way. Threshing can be done by rolling the seed heads between your hands.You can also place the seeds in a large cloth bag such as a pillow case or a feed sack, and beat it on the floor, or use your feet, a broom handle or a board. If the seed head is not too tough, you can sometimes press the seeds through a screen, as described below.
Winnowing is the step of separating the seed from the rest of the seed head material and chaff. On moderately windy days, this can be done by gently tossing seeds into the air for the wind to catch the chaff, although this requires practice and a reliably consistent wind speed. The chaff can also be separated by swirling the seed material in smooth metal bowl, collecting the chaff on top, then tipping the bowl and blowing the chaff away. Before winnowing, consider separating most of the chaff out of the seeds by using screens of various dimensions.
For fruits and vegetables with seeds contained in wet fleshy material, like tomatoes, first remove the seeds from the fruit by scraping them out or crushing or mashing the fruit. Notice that tomato seeds have a gelatinous sac around the seeds.This sac contains compounds that are germination inhibitors, preventing the seeds from germinating inside the mother fruit. After all, a tomato is full of moisture and is often warm - the perfect germinating conditions. For these fruits, let the seeds sit in the pulp and juice for several days before washing. The pulp and seeds ferment, and mold eats the sac off the seeds in a few days.
Plastic containers such as Tupperware, yogurt containers, plastic bowls, milk or juice gallon jugs that are cut open, and five-gallon plastic buckets are all good containers for wet processing. Fruits can be pulped, fermented, and cleaned in the same container.
To wash the seeds free of pulp and juice, add at least twice as much water to the mixture in a bowl or bucket and stir. Non-viable seeds will float, and can be poured off with the water and fruit debris. Repeat this process until only clean viable seeds remain at the bottom of the container. For the final rinse, put the seeds in a strainer and rinse under running water.
To dry the seeds prior to storage, spread them thinly onto a cookie sheet, screen, glass or ceramic dish, or piece of plywood. Do not use paper or cloth since the seeds will stick to it. Seeds should be dried quickly, out of the direct sun, and below 96° F. In humid areas, a fan may be used. Stirring the seeds frequently hastens drying.
When properly stored, seeds can retain their viability for several years. Viability is compromised if seeds are harvested prematurely and if storage conditions fluctuate. When storing seeds, it is essential to keep them in a cool, dry, and consistent environment that protects them from high temperatures, moisture, and direct sunlight. Do not store them in a greenhouse or leave jars of seeds in the sun while gardening, as you will cook your seeds very quickly. Assign a "seed mother or father" to make sure the seeds are kept in the shade and paper seed packages are not placed on the soil where they will absorb moisture and rot.
Store seeds in airtight containers, preferably glass or metal. Glass jars with rubber gaskets, such as baby food jars and canning jars, are perfect. Gallon jars can be used, ideally with homemade gaskets cut out of bicycle or car tire inner tubes. Envelopes of various sizes are good for storing relatively small amounts of seed. You can record the species, variety names, and harvest dates on the envelopes. Coin envelopes work well for seeds as they can be sealed or closed with a paper clip. You can also make your own seed packets. A template is available at www.tipnut.com/seed-packets or see the GSN Resources section. Common plastic bags, such as bread bags, are not moisture-proof and should be avoided. If you want to use plastic bags, use a heavy plastic such as Zip Lock™ or Seal-A-Meal™, and store the smaller seed bags together in a glass jar. Paper envelopes and small muslin bags labeled with the species and variety can also be used in this way. This enables the storage of several varieties of a species together in one container.
Silica gel can be added to jars to desiccate moisture if you are concerned about variations in humidity. Color-indicating silica gel is available-the small plastic-like beads turn from deep blue to light pink as they absorb moisture. They can be dried out and reused by microwaving them or setting them in a 200° F oven for about eight hours.
It is important to keep good records when saving seed. Most important is the labeling of your seed material with the species name, variety, and date of harvest. If you have the resources and inclination, several other pieces of information can be very useful, especially if you plan to share your seed or if it will be used within a community or organization. Additional helpful information to record: common names; historical or cultural information; location grown; germination rate; days to maturity; plant descriptors such as height, fruit size, color, and shape; productivity; ideal growing conditions; and theoretical seed viability.
Although seeds stored under proper conditions can remain viable for several years, viability naturally declines over time and it is important to grow plants out regularly and save new seed. Expected seed viability varies depending on the species, ranging from only one year (e.g. parsnip, garlic, Jerusalem artichoke) to 10 years (e.g. cucumber). Seed viability data is provided for many vegetables in Seed to Seed, a seed-saving guide.
Keeping record of the harvest date of your seeds enables you to make decisions about growing out your stock to retain its viability. You may want to record the theoretical seed viability in the same place as the harvest date for easy reference in future planting decisions.