When buying seeds for your garden, the terminology can seem overwhelming. Open-pollinated. Self-pollinated. Heirloom. Or hybrid. How does a gardener choose? Maybe you're interested in saving seeds. Maybe you prefer vegetables grown from seeds passed down for generations. Or maybe you're even trying to create your own vegetable varieties. Whatever your garden goals are, it's time to go back to biology class and re-familiarize yourself with the terms. Once you do, you'll be able to purchase and save seeds with confidence, knowing that next year's crop will yield fruitful results.
Open-pollinated plants require the wind, insects (pollinators like bees), or the gardener to help pollinate the flowers so they can set fruit and produce seeds. In some cases, the plant will produce both male and female flowers, like squash or pumpkin plants. If this is the case, moving the pollen from a male flower to the stigma of a female flower is all that is needed. The seed of open-pollinated plants, when planted in subsequent years, will yield the same type of plant as its original. Gardeners call this "true to seed" growing. For instance, if you have a "Musque de Provence" squash plant, and you've ensured no cross-pollination, the resulting seeds you save from your crop will grow the same "Musque de Provence" variety next year.
Self-pollinated plants are those that grow what's considered "perfect" flowers—both the pistil and stigma are present in the same flower. Often, all that's required for pollination is simple blooming, which will transfer the pollen to the stigma. There is some evidence that self-pollinated plants pollinate better with the help of wind or from the gardener giving the plant a shake now and then. But in general, self-pollinated plants manage pretty well on their own.
Cross-pollination is common for any open-pollinated plant and can certainly happen with self-pollinators, too. (Do note: self-pollinated plants fall under the umbrella term "open-pollinated," too.) For instance, if a bee visits one tomato plant and then lands on another, it could end up cross-pollinating. If you're interested in saving seeds and keeping the seed true, make sure to isolate your self-pollinators, just to be sure. Examples of self-pollinators include certain types of tomatoes and peppers.
Heirloom plants are always open-pollinated or self-pollinated. This can be confusing, however, because not all open-pollinated plants are heirlooms. The term "heirloom" refers to a plant or variety of vegetable that's at least 50 years old and is either open-pollinated or self-pollinated (according to Seed Savers Exchange). Today, you'll see terms like "new heirloom" in garden catalogs. But when you think of an heirloom as the equivalent of a vegetable "antique," you realize this term is just marketing hype. How can something new be an heirloom? It can't. Instead, the plant in question is a newly-introduced open-pollinated (or self-pollinated) variety.
A hybrid plant is a cross between two different types, or varieties, of plants. Growers hybridize a vegetable by isolating the most coveted traits from one variety and combining them with traits from another to form a totally new offspring. For example, a plant breeder may have an open-pollinated tomato plant that produces vigorously, but the fruit is sub-par. Then, he also grows an open-pollinated tomato plant that produces terrific fruit but has a wimpy production. Next, he spends years working with the plants, growing them and selecting seeds from each that contain the best attributes (in this case, vigor and flavor). Once he's satisfied with his seed selection, he then grows the plants separately and cross-pollinates them. The resulting plant yields a high production of wonderful tasting fruit.
That said, never save seeds from a hybrid. Since they don't grow true to seed, the resulting plant will be a version of one of the two original open-pollinated varieties.