AMES, Iowa -- The late growing season is a good time to collect seeds from vegetables and flowers. Seed saving allows gardeners to preserve heirloom varieties or their favorite plants from year to year. In this article, Iowa State University Extension and Outreach horticulturists answer questions on the basics of harvesting, preparing and storing seed from your garden.
Which plants are easiest to save seed from?
It is easiest to save seed from varieties of vegetables and plants that are open-pollinated. These seedlings typically resemble the parent plants as long as they are not allowed to cross pollinate with another variety of the same species. In contrast, F1 hybrids are produced by crossing two specific varieties and planting the resulting seed. Seed saved from hybrid plants will not produce progeny that resemble the parent plant and, in many cases, they produce inferior fruit or flowers.
Self-pollinated varieties of plants are easier to save seed from than cross-pollinated types. Self-pollinated plants do not require an external vector, like wind or an insect, for pollination and are more likely to produce seed that resembles the parent plant. When an open-pollinated plant requires cross-pollination, you can still get true-to-type seed if you only grow one variety of that species in any given season. These plants can also be isolated by distance, grown in containment tents made of netting, or grown at different times of the year to produce true-to-type seed.
The easiest plants to save seed from are annuals that are open-pollinated and self-pollinated. Beans, lettuce, peas, tomatoes and peppers are great vegetables for beginning seed savers. Flowers great for seed saving include marigold, zinnia, morning glory, cleome, nasturtium, poppy, snapdragon and sunflower.
When and how do I harvest seeds to grow next year?
The precise timing of seed harvest will vary from species to species. Collect seed after it’s been allowed to reach full maturity. Just as flowers and fruit form at different times on the plant, seed will mature at different rates. Collect individual pods or fruit that contain seeds throughout the growing season as they mature. When seeds are in dry husks or pods, leave them on the plant to dry as long as possible. If conditions become too wet or cold, entire plants can be harvested and hung to allow seeds to fully mature.
Harvest seed from the best performing plants in the garden. Save seed from the plants with the best color, tastiest fruit, most-desirable form or growth habit, and that exhibit the fewest disease issues. This will ensure that future generations will perform well in your garden and produce the most desirable plants, flowers and fruits.
How do I prepare seeds after harvest?
Cleaning methods for seeds will vary from species to species depending on whether the seeds are in dry or fleshy fruit. Seeds in dry fruit, such as lettuce, radish, grains, beans, peas and cole crops, are typically dry-processed. The mature seed can be separated from the chaff in several ways. Threshing, smashing and shelling can be used to physically separate the seed from the flower head, husk or pod. Screening with colanders, sieves or other screen materials can also be used to separate seed from chaff. Winnowing separates heavier seed from lightweight chaff by using a fan to blow away the chaff. Seed lots are often screened or winnowed several times to remove as much chaff as possible.
Seeds in fleshy-fruit, such as tomato, pepper, squash and melons are typically wet-processed. The fruit is cut open and seeds removed. Place seeds in a large bowl, add water, and agitate to separate pulp from the seeds. Plant debris, pulp and nonviable seeds will float to the surface and can be decanted off the top. Repeat the process until the water is fairly clear. Some species, like squash, benefit from soaking for a few hours to loosen the pulp clinging to the seeds. Other species, like tomato, may need to be fermented to break down and loosen the gelatinous covering around the seed. The seeds can then be rinsed using running water and a colander or screen. When completely clean, it is important to dry the seeds as quickly as possible. Spread seeds over screens, coffee filters, sheet pans or plywood and provide good airflow. Do not dry seeds on paper or cardboard as they will stick, and avoid drying in high temperatures (over 95 degress Fahrenheit) and direct sunlight. Once seeds are fully clean and dry, they can be stored.
How do I store seeds?
Proper storage conditions for seeds are essential to maintain viability and good germination at planting time. Seeds should be kept dry and cool. Ensuring the seed is dry after cleaning and processing is the most important step to successfully storing seed. Place seed in labeled envelopes. In a separate envelope, place an equal amount of silica gel. Place both envelopes into a clean glass jar and seal shut. After one to two weeks, the seed should be sufficiently dry for storage. Remove the silica gel and return the envelope to the glass jar. Some seed may dry sufficiently utilizing a fan in a seed drying cabinet. Avoid the use of a food dehydrator to dry seed as they usually get too warm and damage the seed. A sealed glass jar can keep excess moisture out and protect seeds from pests like mice or insects. Store jars in a cool, dry location such as a cool closet, root cellar, or a refrigerator. Test the germination rate on the seeds about one month prior to planting.