Types of Seeds: Heirloom, Hybrid, and Open-Pollinated

To save seeds that are healthy, vigorous, and true-to-form, it’s important to understand the different seed types available in today’s market.

Cherokee purple heirloom tomato

‘Cherokee Purple’ is an heirloom tomato that has roots with the Cherokee tribe that pre-date 1890. It’s known for its beautiful color, superb sweet flavor, and large-sized fruit.

Photo by Brian Dunne (bbdunne@southern.edu)

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One of the more important decisions every gardener makes is the choice among hybrid, heirloom, and non-heirloom open-pollinated seed cultivars. Each of these seed types has something to offer, depending on the gardener’s needs, interests, and values.

For seed-saving purposes, the most significant distinction among these types of seed is that gardeners can save true-to-type seed from open-pollinated and heirloom cultivars, but not from hybrids. Following are a few more distinctions that might help you decide what seed types to grow in seasons to come.

Defining Open-Pollinated, Heirloom, and Hybrid

Open-pollinated plant cultivars are pollinated by insects, birds, wind, or other natural mechanisms. Open-pollinated plants may also be pollinated by hand to help ensure that the seed remains pure. Because there are fewer restrictions on the flow of pollen among individuals, large populations of open-pollinated plants tend to be more genetically diverse. This in turn can allow individuals in the population to more readily adapt to local growing conditions. As long as pollen isn’t shared among different cultivars within the same species, the seed produced will remain true-to-type year after year.

Heirloom plants are time-tested and have a history of being passed down within a family or community, similar to the generational sharing of heirloom jewelry or furniture. An heirloom plant cultivar must be open-pollinated, but not all open-pollinated plants have been passed down long enough to be considered heirlooms. While some companies create heirloom labels based on dates (such as a cultivar that is more than 50 years old), the nonprofit Seed Savers Exchange (SSE) defines heirlooms as cultivars that have been saved and shared by generations of home gardeners.

Hybrid plant cultivars are often created through a controlled method of pollination, in which the pollen of one species or cultivar is transferred by human intervention to fertilize the flowers of another species or cultivar. Hybridization can occur naturally, but commercially available hybrid seed, often labeled as F1, is deliberately created to elicit desired traits in the resulting plants. The first generation of a hybrid plant also tends to grow better and produce higher yield than the parent cultivars due to a phenomenon called “hybrid vigor.” However, any seed produced by F1 plants is genetically unstable and shouldn’t be saved for use in following years unless you are looking to develop new cultivars. The resulting F2 generation of plants won’t be true-to-type and may be less vigorous. Gardeners who use hybrid plant cultivars must develop or purchase new seed every season to produce plants that exhibit the same characteristics. It is possible for advanced growers to eventually stabilize hybrids and develop them into open-pollinated cultivars by growing, selecting, and saving the seed over many generations.

While some folks mistakenly equate hybrid seed with new, modern, and genetically modified (GM) seed, humans have been creating plant hybrids for thousands of years. And only within the past 33 years have some modern hybrids and non-hybrid plants been developed using advanced GM technology.

Promoting Seed Diversity

When saving seed from a small garden, it’s important to consider the effects of “bottlenecking” — the loss of genetic diversity in a plant population due to garden-specific selection pressures and small sample size. The best way to avoid bottlenecking and the potential loss of performance characteristics is to inject diversity back into your home population. You can accomplish this by obtaining fresh seed from a grower who knows how many plants and fruits need to be sampled to preserve at least 95 percent of the population’s gene pool from generation to generation. In the case of flour corns, for example, it’s prudent to save seed from at least one ear of 200 individual plants each year to maintain the population’s diversity.

Benefits of Different Types of Seed

While hybrids may provide the benefits of vigorous growth and higher yields, choosing open-pollinated cultivars can help conserve the genetic diversity of garden vegetables and prevents the loss of unique cultivars in the face of dwindling agricultural biodiversity. Furthermore, focusing on heirloom cultivars creates a historical connection to gardening and food production while building a more sustainable and resilient future for our food system.

By choosing open-pollinated and heirloom cultivars, you have the ability to help conserve biodiversity and contribute to the stories behind our seeds.

Learn more about seed saving and SSE’s collection of heirloom vegetable seeds at www.SeedSavers.org.