Buying organic seeds, buying seeds from seed companies that have signed the safe seed pledge (stated in their catalogs), buying seeds from companies that test seeds for GMO contamination, and asking seed companies if they screen for GMO seeds are ways that help assure that seeds have not been genetically altered or contaminated with transgenes during production and storage.
Please check the Council for Responsible Genetics for FAQs about GMO seeds and a list of seed companies that pledge to offer exclusively non-GMO seeds.
Additionally, the Garden of Eatin’ website lists seed companies that haven’t signed the non-GMO pledge, but claim they are also non-GMO. There is also a list of at this site of companies to avoid.
Seed companies we recommend include: