What constitutes an heirloom anyway? The answer to this depends on who you ask, so I will include a few opinions:
1. Heirloom plants are open-pollinated and were more commonly grown prior to the industrialization of agriculture, before genetic diversity was traded for sturdiness, productivity and high yield.
2. A cultivar that has been nurtured, selected, and handed down from one family member to another for many generations.
3. One school of thought places an age or date point on the cultivars. For instance, one school says that the seeds must be over 100 years old, others 50 years, and others pick an arbitrary date of 1945 which marks the end of World War II and roughly the beginning of widespread hybrid use by growers and seed companies or industrial agriculture.