Heirloom seeds are non-gmo by definition. Heirloom varieties are cultivars from gardeners, or communities of gardeners, that have been saving seeds for years, even generations. There is a debate about how old a variety has to be before it is considered an heirloom variety. Some think the variety needs to be 100 years old, others feel 50 years is enough.
Hybrid varieties became popular with seed companies and gardeners around the 1950's. With the advent of hybrid varieties, not as many gardeners saved seeds. We at Garden Seeds want to encourage you to save your own seeds from the heirloom or landrace garden varieties you grow. But, we realize that it is not realistic to expect everyone to have the time or ability to same all your own seeds. That is why we have a list of heirloom seed companies.