Like many other businesses, agriculture has become specialized: farmers carry out only the steps actually involved in growing plants or animals -- none of them make their own tractors or compound their own weedkillers. Most farmers go even further, and grow only a few kinds of crop or animal. In North America, many farmers raise only a single crop, often corn.

One part of this specialization surprises many people: few farmers save seed from one harvest to plant for the next crop. The vast majority of farmers planting nearly all kinds of crops buy their seeds from seed companies. This is true not only of "traditional" farmers in developed countries, but also of "organic" farmers and farmers in poor countries.

There are two reasons most farmers buy from seed companies, one economic and one biological.

The economic reason is that storing seed is not as cheap or as easy as it sounds. Growing plants for seed sometimes requires different techniques than growing plants for for food. The seed itself then needs to be purified to remove insects (and their eggs), weed seeds, and other pests. The seed also needs to be checked to be sure it doesn't carry any diseases which would infect the next crop. Finally, the seed needs to be stored so that it remains viable, and neither sprouts nor rots in storage. Few farmers have the equipment or skill to do all these things.

The biological reason is that most plants with good traits don't breed true -- some are even hybrids. Seed from these plants won't generally grow into plants with the traits the farmer wants, be they high yields in North America, or drought tolerance in Africa.

Seed companies have been around for a long time. In the United States, the first one, David Landreth and Sons, was founded in 1784. Since that time, they've gradually grown in importance, especially in the twentieth century, when they developed many new varieties and hybrids of plants. Today, seed companies large and small provide nearly all of the seeds planted world-wide.

Biotechnology is unlikely to increase seed companies' market dominance, since there's little room for them to increase it. Nor will contracts that forbid farmers from saving seed really matter, since few farmers bother anyway.