Ames, Iowa-The late growth period is a good time to collect seeds from vegetables and flowers. Seed preservation allows gardeners to preserve heirloom varieties or their favorite plants year after year. In this article, Iowa State University extension and outreach gardeners answer questions about the basics of harvesting, preparing, and storing seeds from your garden.

It is easiest to preserve seeds from various open-pollinated vegetables and plants. These seedlings are usually similar to parent plants, as long as they are not allowed to cross-pollinate with other varieties of the same species. In contrast, F1 hybrids are produced by crossing two specific varieties and planting the resulting seeds. Seeds preserved from hybrid plants will not produce offspring similar to the parent plants, and in many cases they will produce poor-quality fruits or flowers.

Self-pollinated plant varieties are easier to preserve seeds than cross-pollinated varieties. Self-pollinated plants do not require external agents (such as wind or insects) for pollination, and are more likely to produce seeds similar to their parent plants. When open-pollinated plants require cross-pollination, if you plant only one species of that species in any given season, you can still get true types of seeds. These plants can also be separated by distance, planted in shelter tents made of nets, or planted at different times of the year to produce true types of seeds.

The easiest plants to preserve seeds are open-pollinated and self-pollinated annual plants. Beans, lettuce, peas, tomatoes, and peppers are good vegetables to start seed preservation. Flowers suitable for seed preservation include marigold, zinnia, morning glory, citrus, nasturtium, poppy, snapdragon and sunflower.

The exact time of seed harvest varies from species to species. Collect seeds after they are fully mature. Just as plants form flowers and fruits at different times, seeds also mature at different rates. Collect individual pods or fruits containing seeds at maturity throughout the growing season. When the seeds are in a dry husk or pod, leave them on the plant to dry as long as possible. If the conditions become too wet or too cold, the whole plant can be harvested and hung up to allow the seeds to fully mature.

Harvest seeds from the best performing plants in the garden. Preserve seeds from plants with the best color, the most delicious fruit, the most ideal morphology or growth habit, and the least disease. This will ensure that offspring will perform well in your garden and produce the most desirable plants, flowers and fruits.

Seed cleaning methods vary from species to species, depending on whether the seeds are dried or fleshy. The seeds in dried fruits, such as lettuce, radishes, grains, beans, peas, and rape crops, are usually processed dry. The mature seeds can be separated from the chaff in a variety of ways. Threshing, crushing and dehulling can be used to physically separate seeds from flower heads, husks or pods. Screening with a slotted spoon, sieve or other screen material can also be used to separate seeds from the chaff. Winnowing uses a fan to blow away the chaff to separate the heavier seeds from the light chaff. Seed batches are usually screened or winnowed multiple times to remove as much husk as possible.

The seeds in fleshy fruits, such as tomatoes, peppers, pumpkins, and melons, are usually wet processed. Cut the fruit and remove the seeds. Put the seeds in a large bowl, add water and stir to separate the pulp from the seeds. Plant fragments, pulp, and non-viable seeds will float to the surface and can be poured out from the top. Repeat this process until the water becomes quite clear. Some species, such as pumpkins, can loosen the pulp attached to the seeds by soaking for several hours. Other species, such as tomatoes, may require fermentation to break down and loosen the gelatinous covering around the seeds. You can then use running water and a filter or sieve to rinse the seeds. After complete cleaning, it is important to dry the seeds as soon as possible. Sprinkle the seeds on a sieve, coffee filter, pan or plywood, and provide good airflow. Do not dry the seeds on paper or cardboard as they will stick, and avoid drying at high temperatures (above 95 degrees Fahrenheit) and direct sunlight. Once the seeds are completely clean and dry, they can be stored.

Proper storage conditions for seeds are essential for maintaining vigor and good germination during planting. The seeds should be kept dry and cool. Ensuring that the seeds are dried after cleaning and processing is the most important step for successful seed storage. Put the seeds in a labelled envelope. In a separate envelope, put an equal amount of silica gel. Put the two envelopes in a clean glass jar and seal them. After one to two weeks, the seeds should be dry enough for storage. Remove the silicone and put the envelope back in the glass jar. Some seeds can be fully dried using a fan in the seed drying cabinet. Avoid using food dehydrators to dry the seeds, as they often become too hot and damage the seeds. The sealed glass jar prevents the ingress of excess water and protects the seeds from pests such as mice or insects. Store the jars in a cool, dry place, such as a cool closet, cellar, or refrigerator. Test the germination rate of the seeds about one month before planting.

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