Vegetable seeds come in three basic varieties: open-pollinated, hybrid, and organic. Some gardeners advocate and plant only a single variety; others mix at will. Each seed variety contains a range of vegetable types. If you want to grow an heirloom garden, for example, you will find open-pollinated seeds available for lettuces, greens, carrots, beets, and especially tomatoes. Knowing how seed varieties are produced, determined and designated will help you grow the kind of vegetable garden you want.
Open pollination is the pollination of seeds by natural means: wind, birds, and insects. Even though our school lunch may contain carefully hybridized vegetables, the naturally-conducted pollination process we read about in class is what is called open pollination. For most vegetables, this means fertilization with pollen from the same kind of plant; in a patch of Brandywine tomatoes, bees go from one tomato plant to another, enabling the growth of more Brandwines. If you save seeds at the end of the growing year and plant them the following spring, they will grow up true-to-type, that is, as more Brandywines. This is what farmers have done for centuries. The upside is consistency in what you grow--that great Brandywine taste every time. The downside is that a whole crop of the same plants (called "monoculture") can be lost to a disease to which the type is susceptible. The best known example of this is the Irish Potato Famine, where blight was unstoppable in the single type of potato planted all over Ireland.
Famines like the Irish were one reason that breeders following botanists' discoveries about cross-breeding within plant types (Mendel's "Experiments in Plant Hybridization" was published in 1865). Joining the disease-resistant qualities of one tomato type with the delicious flavor of another's fruit was painstaking work that became a lifetime career for seed-breeders like W. Atlee Burpee. Home gardeners and farmers alike were eager in the early 20th century to trade consistency for durability. One suspects that some of the reports in the 1970s and '80s, announcing a square tomato, specifically designed for easy packing and shipment, were highly overdrawn. Hybridization, however, greatly increased the range of vegetables, fruits and flowers available throughout the country because specific concerns could be addressed in breeding. Hybridized seeds must be purchased every year; saved seeds do not grow predictably true-to-type.
While both open-pollinated and hybridized seeds may be encouraged to grow with the aid of chemical fertilizers, weed killers and pesticides, seeds that are eligible for organic certification may not. Organic seeds must come from organically grown plants, as regulated by National Organic Program standards. The only exception is that non-certified seeds may be grown and their produce certified organic only if a certified seed is unavailable. Seeds are chosen from among open-pollinated types.
Among commercial and recreational vegetable growers, seed-selection is influenced by a number of concerns. Both open-pollinated and organic growers base their efforts on preserving biodiversity (some "old-time" seeds grow well only in certain areas and ship poorly, leading farmers who grew them to shift to newer hybrids). They also point to what may be left out in hybridization--the taste of a square tomato may resemble the sound of one hand clapping. Hybridizers point with pride to liberating food growers from devastating diseases and insect damage, suggesting that the use of chemicals must be intelligently balanced against human hunger. Be aware of these concerns as you create your own garden--and enjoy your vegetables!