Open-pollinated (OP) varieties
Open-pollinated (OP) varieties produce true-to-type offspring that closely resemble their parents by sharing specific traits, provided no cross-pollination with other varieties was involved. They are naturally pollinated by insects, birds, wind or manually by humans. Thanks to an unrestricted movement of pollen between individuals, this result in a greater genetic diversity within the plant populations, allowing plants to gradually adapt to local growing and climate conditions as well as diseases over the years.
Heirloom varieties
Heirlooms – also referred to as heritages – are plant varieties that carry a history of being passed down and preserved within a family or community over several generations through careful selection. These were commonly grown during earlier periods in human history. Today, gardeners, homesteaders, as well as seed saving groups and activists are striving to maintain and preserve this heritage in danger of extinction. Note that while an heirloom must be open-pollinated, not all open-pollinated plants are heirlooms.
Hybrid varieties
Hybridization is a controlled method of pollination where a crossing – often deliberate – between two genetically distinct parents is made by human intervention in order to breed a desire trait. In most instances, the new plant created and its seeds become the patented property of the breeding juridical entity. Commercially available hybridized seeds (also known as “F1” for “first filial generation”) are extensively used within commercial farms and intensive agriculture as they give highly predictable, homogenous, resistant, and high-yield plants, maturing simultaneously. Those standardized factors make them easier to grow, harvest, store, transport, and sell. However, they are frequently nutritionally inferior compared to open-pollinated varieties. Due to hybrid vigor (also called heterosis), the first generation tends to grow better and produce higher yields, especially for crops subject to strong inbreeding depression (discussed here) such as corn and many brassicas. Offspring that are produced from such crosses may, however, vary greatly from their parents and will result in either genetically unstable or sterile plants in the next generation (F2). Should the seeds from F1 plants saved, their offspring will indeed fail to grow true and will often be less vigorous, therefore forcing gardeners to purchase new seeds every year. F1s can however be stabilized over several years of careful selection through a dehybridization process.
Commercial hybrid seed production is essentially driven by the financial advantage conferred by the production and promotion of proprietary varieties that no one else can multiply in their original form. While hybridization is a phenomenon that occurs spontaneously in nature, the large-scale industrialization and monocultural disposition of such a production threaten the preservation of plant biodiversity and genetic heterogeneity, fueled by unsustainable, intensive and ecologically destructive agricultural practices. This makes commercial hybrids not well regarded among grassroot gardeners and permaculture enthusiasts, who then tend to favor and support open-pollinated and heirloom varieties instead.