Heirloom produce, flowers, seed, and books about heirloom foods keep trending. But what exactly does "heirloom" mean? The first thing to understand about heirloom is that there is no single or legal definition for the term. It is open to some (occasionally heated) interpretation. This can be frustrating for gardeners who want to understand what they are planting, what they should plant, and why. It also complicates our eating and farmers' market shopping lives: What is heirloom?
Reduced to a sentence, heirloom produce is the result of a type of pollination, repeated over time. Here is the heirloom equation: Open Pollination + Heritage = Heirloom.
The first part is unequivocal: Heirloom plants are open pollinated—the result of natural selection rather than of controlled hybridisation. All heirloom seeds are open pollinated, but not all open pollinated seeds are heirloom. Open pollination is when wind and insects carry pollen spontaneously from one plant to another. The result of open pollination is seed that produces plants whose characteristics remain fairly—but not absolutely—consistent from one generation to the next. As a result, heirloom varieties may vary in appearance.
In open pollinated fields plants that veer too far from an established heirloom variety's standards are generally removed. Culling highly unusual plants prevents them from pollinating others and producing too much variation.
By contrast hybrid plants are usually the result of controlled pollination (although hybridisation can occur spontaneously): two different parent plants are chosen by a grower to combine specific and desirable characteristics from each. These characteristics are reflected in the hybrid child plant. Hybrids are uniform and predictable from one generation to the next.
The broader sense of what heirloom means is associated with heritage, history, and nostalgia. In short, heirloom is seed saving. Heirloom plants are understood to grow from seeds handed down from one generation to the next. Hardcore heirloom wisdom suggests that a plant can only claim heirloom status if it has a minimum pedigree of 50 years. Or even before the hybrid breeding boom, post-World War II. So, in theory, you can begin a new heirloom tradition now, saving the seed of a new, open pollinated plant, knowing that it will only qualify as heirloom in 2059!
The heritage aspect of heirloom also encompasses plants that were not grown commercially, but by small farmers, families, and individuals within a community to be used by that community. Seed saving ensured the continuation of a plant that was not bred to travel long distances without blemish, for example, like the spookily perfect, round, scarlet 24/7 supermarket tomato. This sense of heritage can also mean the rescue or revival of a vegetable, fruit or flower that has come close to disappearing from cultivation. Seeds saved from a community that no longer exists, can bring that tradition back to life.
Understanding that heirloom plants grew for generations in a specific place is important. Seeds from heirloom tomatoes that grew for decades in the Hudson Valley, with its particular soils, humid summers, and local pests, will carry traits that are best adapted to those conditions. They will be different from seeds collected from tomatoes grown by families in southern California, with dry summers, and supplemental watering. The New York-origin plants will not fare as well in California. Because they can be better adapted to certain environmental stressors such as drought or flooding "this can make them incredibly delicious but also sometimes inconsistent in their performance," says Sarah Owens, the author of the new cookbook, Heirloom: Time-Honored Techniques, Nourishing Traditions, and Modern Recipes.
Regional specificity is why heirloom produce is most often found at local farmers' markets; and it is part of the heirloom appeal. Heirloom produce in its most true form belongs to a place. Regional seed saving companies address and market this aspect directly, while large seed companies sell ubiquitous heirlooms (think 'Brandywine') that anyone can cultivate, anywhere.