There is no one single definition for an heirloom plant variety.
Generally they are thought of as older varieties (originating before the 1950s) that have been preserved and passed on through multiple generations of gardeners through seed saving. They were chosen because they expressed some remarkable trait such as high yield, unique flavor, color or shape, exceptional disease resistance, heat tolerance, adaptability to soil types, etc.
Heirlooms are open pollinated, non-hybrid varieties. This means seeds saved from heirlooms will yield the same or similar plant when sown (a.k.a “grows true”).
Some hybrid varieties stabilize and become open pollinated, but are not considered heirlooms. One day maybe these will become new heirlooms.
There are more heirloom varieties available than we can list. Here we have chosen some of the most popular, unique and best suited varieties for the Portland area.