Choosing Seeds: Hybrid and Heirloom

By Billie Parish, Butte County Master Gardener, March 13, 2015

Spring is around the corner, which means it is time to plant.  Starting from seed can be a gratifying and economical way to grow many edibles and ornamentals, but choosing seeds can be confusing.  Do you want a black tomato or a striped tomato? Organic? Heirloom? Hybrid?  What is the difference?

The definition of ‘heirloom' is not always agreed upon -- some say an heirloom variety must be at least fifty years old, some say it should be older.  But generally speaking, an heirloom seed comes from a plant variety that passed on through several generations within a family or community. Varieties were often chosen for their superior taste, appearance, and overall performance. For example, thanks to John Bidwell, here in Chico we have the Bidwell Casaba, a melon dating back to the late 1800's.

Heirloom varieties must be open pollinated, meaning that pollination occurs naturally by insect, bird, wind, or animal.  Seed produced by the heirloom variety will grow true to type (it will resemble the parent plant) as long as the flowers were pollinated by the same variety.  Open pollination creates a more genetically diverse gene pool which allows plants to slowly adapt to local growing conditions.

Importantly, while all heirlooms are open pollinated, not all open-pollinated plants are heirlooms.  Hybrid seed is produced when open pollination occurs between two specific varieties carefully chosen for their superior traits.  Such controlled cross-pollination producing hybrid seed results in offspring with desired traits, such as disease resistance, uniformity, and greater vigor.  Unlike heirlooms, however, the seed saved from hybrids will not grow true to type in the next generation and will be less vigorous and more genetically variable.

Reliance on a single vegetatively propagated potato variety with no genetic diversity led to the Irish potato famine of the 1840s, when a fungus destroyed the potato crop four years in a row, leading to mass starvation. Because only one variety of potatoes had been planted over and over, the lack of genetic diversity led to potato fields that were highly susceptible to disease.

Hybrids should not be confused with Genetically Modified Organisms, or GMO's.  GMOs are created by inserting genes from one species into an unrelated species. Some of these combinations might seem like creations of science fiction! Although never commercialized, tomato was experimentally modified with genetic material from fish to improve frost tolerance. On the other hand, papaya genetically modified with a viral protein saved the Hawaiian papaya industry from papaya ringspot, a devastating virus disease. 

Although 70% of the processed foods we eat contain GMO ingredients, it is unlikely that the seeds you find in your local nursery are genetically modified.  These types of seeds are primarily used commercially for crops such as corn, soybeans, canola, sugar beets and cotton.

Regardless of what kind of seed you choose, it is important to understand the distinctions among them in order to make informed decisions based on your priorities.