The Meaning of Heirloom, Hybrid and GMO

Here are some simple definitions of seed-related terms you often read about in association with seeds, particularly seeds for vegetables and herbs.

Heirloom Seeds

Heirloom seeds are a variety that has been around for many decades. The seeds themselves are not heirloom, the variety of plant is. These varieties are the results of careful, considered crossing by farmers and home gardeners over several seasons in the hopes of improving a vegetable’s flavor, color, or habit. Examples of popular heirloom varieties include ‘Brandywine’ tomato, ‘Moon and Stars’ watermelon, and ‘Danvers Half Long’ carrot.


Open-pollinated (OP) means a variety “comes true” from seed: if you have two plants of the same variety, you can cross pollinate them and the resulting seed will be nearly identical to the parent plant. This means that you can save the seeds from an open-pollinated variety, plant them the following season, and you’ll end up with a plant that is more or less the same in terms of size, shape, color, and taste of the vegetable you purchased from a seed company. By definition, all heirloom varieties are open-pollinated.

Hybrid Varieties

Hybrid varieties are created by crossing multiple varieties of a plant. However, they differ from heirloom varieties in that they are usually not open-pollinated; that is, they do not come true from seed (there are a few exceptions, however – like ‘Bright Lights’ Swiss chard: too new to be an heirloom, but is, in fact, an open pollinated hybrid). If you buy a hybrid variety from a seed catalog and try to save the seeds, even if you crossed two flowers on the exact same plant, the fruit you get the following season will NOT be the same as the variety you bought. It could be better but it will probably be of lower quality, as hybrid varieties are created through a series of complex crosses that the breeder will not share with the public. The primary breeding goal for most hybrid vegetable varieties is uniformity and pest/disease resistance – the fruits borne by the plant are all roughly the same size, color, and shape. Some examples of hybrid varieties are ‘Big Boy’ tomato, ‘Silver Queen’ corn, and ‘Sugar Baby’ watermelon.

Both heirloom and hybrid vegetable varieties begin life the same way: as the progeny resulting from the crossing of two different varieties of the same type of vegetable. Heirloom varieties are all hybrids – hybrid merely means the result of a cross. However, heirloom varieties are open-pollinated and can be perpetuated through saving the seeds of one season’s crop for the next; Hybrid varieties can only be created through controlled crossing and their parentage is typically rather secret.

Heirloom vs. Hybrid Varieties

There is a great deal of subjectivity and value judgments that swirl around these two notions – there are a lot of “preachers” on the heirloom side who swear that heirloom tastes better and is the only thing worth growing. However, hybrid varieties have a great deal to recommend them: they typically display vigor (you may have even heard the term “hybrid vigor,” which describes crossing plants for stronger, healthier growth) and disease resistance. Often, if you look at a hybrid tomato description or even the little plastic tag in cell pack of tomato plants, you’ll see a code of letters – something like “VFNT.” This means that this tomato is resistant to the common tomato foes: verticillium wilt, fusarium wilt, root-knot nematodes, and tobacco mosaic virus. So for gardeners in areas where these diseases are wide-spread, choosing hybrid, disease-resistant tomatoes is a no-brainer.

What about Organic?

Which brings us to the term “organic.” As it applies to home garden seed, organic means that the parent plants were grown using certified organic techniques – no synthetic pesticides or fertilizers were used to produce or store the seed. But here’s the thing – both heirloom and hybrid varieties can be organic. It is a matter of seed production, not seed origin. So though “heirloom” and “organic” are often tossed about as though they are mutually inclusive, they definitely are not. You can have non-organic heirloom seeds and organic hybrid seeds just the same as you could have organic heirloom seeds and non-organic hybrids.

Genetically Modified Organisms (GMO)

And with that comes the most confusing part and most often misused seed term, GMO. GMO stands for “genetically modified organism” and it means just that – a technician literally goes into the seed and physically inserts a gene from another organism. The process of genetically modifying seeds results in a DNA-level change of a plant’s physical and chemical make-up. Is it bad? Well, here’s the kicker – no one really knows. There have been no studies researching the effects of genetically modified food on humans or the environment. GMO techniques have one primary goal: to make more money for the company producing them. They do not make food tastier, more nutritious, less expensive, or higher yielding. Their benefits are purely profit based, and the profits are solely for the enrichment of the company behind the modification.

To that end, it is currently unlikely that genetically modified varieties will enter your vegetable garden. It is a relatively expensive process and is typically reserved for cash crops (rapeseed, cotton, and most famously, corn). However, since the USDA inexplicably does not require genetically modified food to be labeled as such, there is a possibility that the practice could eventually intersect with the life of the home vegetable gardener. Fortunately, if seed is certified organic, by definition, it cannot carry any genetic modifications. So buying organic seed is one way to be absolutely sure that you don’t buy GMO seed; another option is to only shop with brands and retailers who have taken the Safe Seed pledge to never knowingly buy or sell seed that has undergone genetic engineering.

No More Seed Propaganda

These terms have become loaded and emotional and widely misunderstood, making it difficult for the average home gardener to understand what exactly they mean. Though long-winded, I do hope these definitions take away some of the emotion and propaganda that many other garden bloggers use in discussing the issue.

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