For the novice gardener searching for seeds in a catalog, the array of terms like hybrid, non-GMO, open-pollinated, and heirloom might make the task of deciding among all the tempting descriptions of plants more difficult. Depending on which catalog you read, some types of seeds are almost vilified, while others are ignored.
Almost all seeds on the market for gardeners are either hybrid or open-pollinated. Scientists genetically engineer GMO (genetically modified organism) seeds by inserting genes from plants, bacteria, or other living species into a plant’s DNA in ways that cannot happen in nature. For example, Bacillus thuringiensis, or BT, is a bacteria organic gardeners apply to plants to kill caterpillars. Scientists figured out how to insert the BT gene into corn genes, and the resulting seed kills the corn earworms when they begin feeding on the ear of corn. The corn you eat has the BT gene inside it.
Proponents say this reduces the amount of pesticides introduced into the environment, while skeptics don’t like messing around too much with the natural order of things. You will know it if you buy GMO seed: you will probably have to sign some document saying you won’t sell or even save the seed, and you may have to put up a sign near the field identifying the crop. There is no danger of the home-gardener accidentally buying some GMO seed at the local store and planting it; it’s usually reserved for farmers.
Open-pollinated seeds form when the pollen of one plant is transferred to another plant, usually with the help of wind or insect pollinators. The resulting offspring are similar to the parent plants because plants that are similar genetically cross with each other. Gardeners save seed from open-pollinated plants and expect to get a similar plant from the seed next year. All seeds were originally open-pollinated, and farmers and gardeners were able to save seed from plants that did well in their gardens for free. Once a crop sets seed, they could grow gardens indefinitely, as long as they saved seed from the crop each year, without ever buying any more seed.
Heirloom seeds are usually open-pollinated, and they have some historic or cultural value. They are seeds your great-grandparents might have grown. The definition of heirloom seed varies from catalog to catalog, but some examples are Brandywine tomatoes, Kentucky Wonder beans, and Red Russian kale.
Hybrids pollinate either by wind or with the help of a plant breeder, but the seed grower makes sure pollination occurs in controlled circumstances among varieties of plants that are distantly related. The seed, the offspring of two specific parents, is usually the first generation of the breeding between the two plants that possess desired characteristics. For example, a breeder may cross a tomato resistant to tobacco mosaic virus with a tomato resistant to cracking to get a tomato resistant to both cracking and tobacco mosaic virus. The seed of a hybrid tomato, however, contains the genetic traits combined in an uncontrolled manner and the traits of the offspring are unpredictable. Hybrids often do not even produce seed, or they may produce sterile seed that will not germinate. If you plant hybrid crops, you will have to buy new seed every year. Breeders label seed “F1” hybrid, which denotes the seed as the first offspring of the parent plants.
Each of the types of seed has its own advantages. Hybrids often offer better disease-resistance than open-pollinated varieties, but open-pollinated varieties often taste better and, if you save the seed, you don’t have to buy the seed again.
Harvesting a tomato crop at all has been an ongoing challenge for me because the disease has been killing my plants. Last year, I planted many different types of seeds and the hybrid tomatoes resisted disease the best. A few of the open-pollinated seeds did fairly well too, and I’ll grow them again along with some new types. Last year I actually had a tomato harvest, and, although purists would eschew any seeds not open-pollinated, I am practical: it’s better to grow something in my own garden instead of buying it elsewhere, even if it's from hybrid seed. Planting many different types of seed is the best way to ensure a harvest: if one variety dies, something else may survive.