Heirloom plants, by definition, have some history behind them. Some say an heirloom variety must be at least fifty years old, some say even older. Heirloom seed is described as being from a plant variety that has been passed on through generations. Perhaps more significantly, the word “heirloom” is a marketing term.
Heirloom varieties must be open pollinated, meaning that pollination occurs naturally by insect, bird, wind, or animal, or, in the case of tomatoes, they can self-pollinate. Seed produced by the heirloom variety will grow true to type as long as the flowers are pollinated by the same variety. Open pollination creates a more genetically diverse gene pool which allows plants to slowly adapt to local growing conditions. Importantly, while all heirlooms are open pollinated, not all open-pollinated plants are heirlooms.
Open-pollinated plants reproduce through natural pollination methods such as wind, insects, or self pollination. Many varieties of tomatoes are designated as open-pollinated, but not heirlooms, maybe due to their history of production not being long enough to earn the term “heirloom.” These plants are genetically stable, meaning they will produce offspring that are true to type, as long as pollinated by the same variety.
Hybrid plants are developed manually by breeders to cross-pollinate two “parent” plants, each chosen for particular traits. For example, one parent might be desirably sweet, while the other has large fruit). The seeds from this first-generation cross are referred to as F1 hybrids. This process is carefully planned to produce offspring with specific, desirable traits from both parent plants. Unlike heirlooms and other open-pollinated plants, the seed saved from hybrids will not grow true to type in the next generation and will be less vigorous and more genetically variable.
It should be pointed out that hybrid plants are not genetically modified or GMO plants. A GMO plant, or genetically modified organism, is a plant that has had its genetic makeup altered using biotechnology techniques, allowing scientists to change specific characteristics of the plant, like making it resistant to pests or herbicides, by introducing new genes into its DNA.
Napa Master Gardeners are available to answer garden questions by email: mastergardeners@countyofnapa.org. or phone at 707-253-4143. Volunteers will get back to you after they research answers to your questions.
Visit our website: napamg.ucanr.edu to find answers to all of your horticultural questions.
