Updated 08 April, 2025

Different people may define the meaning of heirloom seeds differently. Some use the words “heirloom” and “open-pollinated” interchangeably, while others, including True Leaf Market, define heirloom seeds as a subset of the open-pollinated category with a history of 50 years or more of growth. We understand this may seem a bit confusing at first. For greater clarity, we break down the different types of seeds and the top reasons to grow heirloom varieties.

Heirlooms and Other Seed Types

All seeds offered by True Leaf Market are non-GMO (not genetically modified organisms). These can include both open-pollinated and hybrid seeds. Both have their benefits and drawbacks depending on what you prioritize in your garden. Open-pollinated types are best for those wanting to save, trade, or store seeds. Heirlooms fall into this open-pollinated category. Hybrids are best for those wanting the most improved and resilient options on the market. Both open-pollinated and hybrid seeds are produced conventionally and using organic growing practices

Non-GMO Seed

True Leaf Market has signed the Safe Seed Pledge, an agreement to only sell non-genetically modified seeds or plants to “protect the diversity and genetic integrity of our seeds to provide the foundation for a stable, safe food supply for us and for generations to come.” While genetically modified organisms have a lasting history of doing good, such as the production of insulin, reducing the demand for pesticide use, and enhancing the nutritional value of foods in places experiencing disease and deformities relating to nutrient deficiencies, they also come with significant drawbacks over time.

You may be familiar with the phrase, “Nature is the great equalizer.” Through natural evolution, the most resilient and adaptive attributes persist through time. Genetic modification strives to cheat this process by allowing people to pick and choose what attributes end up where rather than allowing the genetic code to evolve and strengthen over time. This is why it is so important to preserve non-genetically modified seeds. Many people fear genetically modified organisms because of the instances where genetic material may be taken from an animal and injected into a plant. While this does happen, it is much more common for genetics to be taken from one plant and integrated into another, as there is a much greater likelihood of compatibility. Regardless of this, True Leaf Market supports the preservation of seeds grown and developed through natural biological processes for greater diversity and stability in food production.

Open-Pollinated Seed

Openly pollinated seeds are able to produce true-to-type characteristics even though they may be cross-pollinated with plants with different qualities. Simply put, open-pollinated seeds produce plants that look, smell, taste, or feel as you would expect them to because their traits have reached a level of dominance. Just as any natural genetic line can, open-pollinated seeds may experience genetic drift over a period of many years. This is why many growers prefer to stick with heirloom seeds that have proven to produce true-to-type harvests over a period of 50+ years.

• Heirloom Seeds

  As mentioned above, heirlooms are open-pollinated seeds that have proven to stand the test of time. Because their genetics have stabilized for multiple generations, the seeds may be harvested and planted year after year, yielding the same expected results. While True Leaf Market considers heirloom seeds to be open-pollinated varieties that have been grown for 50+ years, you may find some seed companies that use 30 years as a benchmark for sustained genetic stabilization. Others may not consider a timeline for stabilizing genetics at all and instead use open-pollinated and heirloom synonymously.

Hybrid Seeds

Hybrid seeds are the misjudged seed of the bunch. They are often confused with genetically modified seeds. Hybrid seeds are NOT GMO’s. They are plants that have been bred using natural biological processes. Just as a dog may be bred with another breed with desirable characteristics, so can plants be crossed and selected for desirable attributes like disease resistance, color, flavor, aroma, etc. Hybridized plants largely fall into two categories: a cross between two different species or the child of an inbred genetic line.

Interspecific and Intraspecific Hybrid Seeds

Hybrid flowers are often developed by crossing between or within species, resulting in new color patterns and shapes. Plants, including petunias, fruit trees, roses, salvia, and amaryllis, are often developed using these methods. The latin name of plants of interspecific hybrids follow a format of Genus species x Genus species while an intraspecific hybrid has a latin nomenclature format of Genus species x G. species

F1 Hybrid Seeds

Vegetables are more commonly bred for desirable recessive traits via inbreeding. Because inbreeding for several generations can lead to weaker plants, it is important to cross the plants with another genetic line to re-introduce genetic variety and produce very healthy, strong plants. This is why you will often see hybrid plants identified as F1 hybrids. This means that the seeds you are receiving are of the first generation that reliably express the desired characteristics, along with a mix of genetics that allows for healthy growth. Hybrid seeds can be developed by controlling which plant’s pollen and ovules are combined via hand pollination instead of allowing cross-pollination by chance via insects.

Growing Practices vs Seed Type

Other considerations for what type of seeds you want to grow should include the growing practices used. Organic seeds and produce are often favored because they support sustainable practices. Organic seeds are not genetically different from conventionally grown seeds of the same variety. They were simply grown using different methods. Organic growing practices limit pesticide and synthetic fertilizer use while prioritizing diversity and soil health. Conventional practices allow for greater pesticide and synthetic fertilizer use, large-scale monoculture plantings, and a significant influence of irrigation and machinery technology.

Why are Heirlooms Best For Saving Seeds?

When it comes to saving seeds, always choose open-pollinated varieties. Avoid saving seeds from hybrid plants because they will likely not produce true-to-type. What exactly do we mean? Hybrid plants have a high likelihood of producing seeds that result in unexpected characteristics because they are a first-generation cross of inbred genetics. Saving the seeds of hybrid plants would be like crossing a domestic housecat of a known breed and a stray field cat. You may get fruit, but it will likely vary from the original F1 hybrid seeds you grew.

How to Find Heirloom Seeds from True Leaf Market

You can easily identify heirloom varieties on trueleafmarket.com by using the side filtration settings, shopping the heirloom seed category, or using our seed finder quizzes. Each heirloom seed will display an icon over the seed image when displaying a category or search result page. On individual seed pages, you may view an heirloom badge.