Seed Saving Basics
Dr. John Navazio, OSA and Micaela Colley, OSA
The brochure, Seed Saving for Farmers & Gardeners, is free and available to download at www.seedalliance.org.
Seed saving started roughly 15,000 years ago. By selecting and saving seeds from best plants and replanting these, we co-evolved with these seeds. Farmers did most of our plant domestication, making edible plants from wild plants. In an amazingly short blip of time, we’ve lost this interaction with our crops. But the fact is that seed saving involves some very accessible skills that anyone can acquire and have success with.
Why save seed? One main reason is to preserve it for the next generation. By choosing to save seed that is well adapted to your environment, you ensure that you will have that particular variety of seed year after year.
A variety is defined as a population within a species that holds common characteristics within the species.
Open Pollinated Varieties are the easiest varieties to work with. These are stable varieties that breed true from seed. Their seeds freely cross with other individuals.
Hybrid Varieties are varieties that are created by crossing two separate, true breeding strains of the same species. Seeds bred from hybrids will not breed true to type. They will segregate out with traits from each of the parental strains. Hybrid varieties often experience fertility issues; it may take a long time to cross hybrid seeds to get desired traits (to create a new variety).
GMO Varieties are covered by plant patents. Genes have been inserted into a segment of the DNA. These genes are often from different species, genera, or even kingdoms (transgenic). You may not save seed from patented varieties.
For seeds to develop, there must be (1) pollination (pollen moves from anther to stigma) and (2) fertilization (pollen moves down into the ovary). Specific climatic conditions are required for fertilization to occur. To ensure success in saving seed, you need to know your crop and the climate conditions necessary for fertilization.
Annual Plants are plants that complete the seed cycle in one season. You must plant annuals early enough in the season to allow the plants to mature and produce seed. In Hawai‘i, you should plan your planting for the wet season in order to harvest seed in the dry season. Seed must be harvested in the dryer time of year. Many diseases can occur if you harvest seeds during the wet season.
Biennial Plants complete their cycle in two years. Carrots, cabbage, and celery are biennials. These plants need about 8 weeks of temperatures below 50 degrees to vernalize. Vernalization means cold treatment—or how much time the plant needs at or below 50 degrees to produce seed. If you don’t have temperatures below 50 degrees, you can dig the plants up and put them in the refrigerator for a few weeks to simulate colder temperatures.
Perennial Plants are plants that produce seed after a year or two of growing.
The value of variety trials is to see which plants produce seeds under which conditions. For example, beets require a combination of vernalization and lengthening days, so it is difficult to get beets to produce seed here. Variety trials help us to see which are adapted to this climate.
99% of true breeding plants cross-pollinate, and all self-pollinating species will cross-pollinate, especially if you raise the humidity and increase biodiversity. If you want to cross them, you can do it. If you don’t want to cross them, be mindful of the distance between plants. Inbreeders like lettuce only need to be 3–5 feet apart to ensure that they don’t cross. Commercial distance recommendations are greater than those for home gardeners to ensure true seed.
Inbreeders require populations of 16–50 plants to produce seeds. Outbreeders require populations of 80–120 plants. If you can’t grow 80 plants, try saving seeds as a group. In New Mexico, small growers plant together to ensure there are enough plants. That’s what traditional seed swapping is about. Everyone shares a handful of the seed produced.
You should follow these guidelines to maintain genetic diversity, population resiliency, and important traits. Take a balanced seed sample to ensure genetic variability.
Allow plants to mature before harvesting seed. Feed the plant and keep it alive as long as possible because the plant is feeding the seed. Allow the seed to set, but not shatter. Harvest at the bulk of maturity—this is the peak window to get the largest harvest of high-quality seed.
To maximize seed harvest, shake plant seeds into a bucket on repeated days, or place drop cloths around plants to catch dropping seeds.
Post harvest, dry the seed. Green houses allow good air circulation for drying seed. Remember to protect seed crops from rain.
Threshing releases seed and breaks up plant material. Or you can stomp seed in a bucket. Use your foot as pressure to grind plant material against plant material to get plants to release seeds.
Wet seeded crops are those in which the seed is held inside fruit. The fruit is harvested ripe. To break the seed apart from the flesh, blend the pulp into a slurry, ferment the slurry for 2–3 days at 75–90 degrees, and stir twice a day. Fermentation breaks down the gelatinous coat on the seed. Be careful because seeds will be wet, decant off the pulp and skin, and good seed will sink to the bottom. Add water and continue to pour off the pulp until you have a pure line of seed. Pour into screen to catch seed and dry quickly, because wet seed exposed to air start germinating. Spread the seed on a screen with a fan to get it to dry as quickly as possible.
Dry seeded crops are harvested by fanning and winnowing—a gravity separation technique. Winnowing separates by density; screening separates by size. Alternate between the two, doing each technique at least 3 times.
Screening for dry seeded crops separates the seeds by size and removes larger chaff and smaller debris to separate out heavy seeds. For this, use a colander, galvanized hardware cloth, or the bottom of nursery trays, which all work well to separate seeds.
Always save a little of the original seed of a variety that you really like, so that you can go back to the original seed if your successive generations lose vigor over time.
The soon to be released “E-extension E-organic database” will describe varieties that do well across the northern U.S. This database will include results of variety trials under organic growing conditions. When it is released, you will be able to search this database by disease, crop, climatic information, soil information, etc., to learn more about different varieties. This is a great potential resource.