Taste: They taste essentially the same as the vegetables our ancestors ate, before flavours were compromised by hybridization.
Appearance: Heirloom varieties are likely to be less uniform in size and appearance than the clone-like vegetables displayed at supermarkets.
Time tested: Heirlooms of all types are defined by West Coast Seeds as "cultivars — that is, cultivated varieties (not wild) that have been deliberately selected for specific characteristics. When grown, harvested and propagated correctly, those characteristics will be retained from one generation to the next." Saved hybrid seeds will not necessarily reproduce from one year to the next.
Open-pollinated: Heirloom foods are open-pollinated, meaning pollination occurs by insect, bird, wind, humans or other natural mechanisms. "Because there are no restrictions on the flow of pollen between individuals, open-pollinated plants are more genetically diverse," says the Iowa-based Seed Savers Exchange. "This can cause a greater amount of variation within plant populations, which allows plants to slowly adapt to local growing conditions and climate year to year. As long as pollen is not shared between different varieties within the same species, then the seed produced will remain true to type year after year."
Not genetically modified: This is an important consideration for those who are concerned about the quality of some of the new species of food being bred by modern science.
Not necessarily organic: Many heirloom seeds are classified as "organic" and many are grown organically, but not all. Consumers looking for "organic" heirlooms should verify this with the seed provider or grower.