While the phrase heirloom seeds is controversial as to exactly what qualifies as heirloom, there is common ground that everyone does agree. Heirloom seeds are seeds that have been handed down from previous generations without any genetic alterations what-so-ever. Heirloom seeds are not the varieties that have been engineered to be rot or mold resistant.
Some vegetables have been altered to be different colors in order to be trendy, a la the purple carrot. Call me a purist but carrots are not supposed to be purple, even if they do taste the same, cook the same, and have the same nutritional value as regular carrots. I have tried them and they taste just fine, but no thank you, not for me.
The most controversial aspect of heirloom seeds is the age of the cultivar. Many believe that when plant breeders first introduced hybrid seeds that were developed from inbred lines in 1951, that is when the unmodified seeds became heirloom, while others focus on seed varieties that were used by the Native Americans. That debate may never end.
Another aspect of heirloom seeds is whether or not it has been open pollinated. When heirloom gardeners refer to open pollination they mean that a particular cultivar can be grown from seed and will be "true to type." For example, I grow Brandywine heirloom tomatoes to sell at the farmer’s market and if I were to collect the seeds and process them properly from the mature fruit, I will get the same traits as the fruit that bore them. On the other hand if I were to use any tomato hybrid seed and process them same way as I did the Brandywine variety, there is a good chance that the seed would be sterile producing no fruit at all. Even if it were to germinate, it may not have any resemblance of the fruit that produced that seed.
Probably the most important aspect of heirloom produce is the flavor. We’ve all enjoyed a big, red fresh tomato that was just minutes off the vine and was juicy and packed with flavor; now compare that with a tomato that you buy at the local supermarket. Enough said?
Have you ever noticed that all the tomatoes at the grocery store all look perfect, and the same size? That’s not an accident; those seeds have been engineered to produce huge crops of perfect looking, cardboard tasting fruit unlike Brandywine tomatoes, that has achieved cult status (really) for being abnormally shaped and ugly, but most importantly, delicious.