Seed regulation has been empirically controversial.

In my new book, “The Food Sharing Revolution: How Start-Ups, Pop-Ups, and Co-Ops are Changing the Way We Eat,” I look at sharing from a variety of angles — good, bad, and downright ugly. One example is the custom of seed sharing, which can be traced from indigenous societies and the earliest fall festivals that ultimately inspired American Thanksgiving.

For centuries, people in agrarian societies shared seeds to help each other subsist from year to year. Today, thanks to intellectual property rights and often well-intentioned laws, our ability to share seeds is restricted. Realizing this, food activists, garden enthusiasts, and community leaders are trying to make it easier by making seeds available through libraries. Surely there’s nothing controversial about that, right? Actually, there is.

Until the early 1800s, U.S. farmers either saved seed from their own crops or obtained it through personal networks. Then in 1819, Treasury Secretary William Crawford called upon all ambassadors and military officers stationed overseas to collect seeds and bring them home, where they would be shared freely.

Initially this program was informal, but in 1839 Commissioner of Patents Henry Ellsworth persuaded Congress to appropriate funds for it. Ellsworth owned large tracts of land in the Midwest, so his motives may not have been strictly public-minded. Soon his office was distributing 60,000 seed packages annually through the U.S. mail. By the turn of the 20th century, the Department of Agriculture was shipping a billion free packages of seed each year.

This was relatively uncontroversial until 1883, when a group of representatives from mostly vegetable seed trade firms formed the American Seed Trade Association. No business model can work if the government gives away for free what private merchants want to sell.

After decades of lobbying, the group convinced Congress to end the free seed program in 1924. Without granting ownership rights to plant breeders, members argued, there would be no incentive to “improve” seed for qualities such as yield, tolerance, germination length, root depth, or aesthetics. As two plant breeders put it in 1919:

“The man who originates a new plant which may be of incalculable benefit to the whole country gets nothing — not even fame — for his pains, as the plants can be propagated by anyone.”

The 1930 Plant Patent Act was a watershed. It initially applied only to nursery plants propagated through cuttings, such as roses and apple trees. Soon, however, breeders of agricultural commodities pressed to expand the law in recognition of their labor. As a result, the majority of commercial crops and garden plants in use today were developed by agricultural companies, to the point that three companies — Bayer Monsanto, DuPont, and Syngenta — account for roughly 50 percent of all global seed sales.

Today, the seed industry is highly controlled. Every state has laws that require suppliers to obtain licenses, test seeds to ensure they are the variety advertised, and properly label them. And the federal government regulates seed sales across state lines.

These laws exist for good reason. If farmers buy seed that turns out to be the wrong variety, or doesn’t germinate, their livelihood is at risk. Seed laws hold providers accountable and protect buyers. Some laws apply even to those who offer seeds for barter, exchange, or trade.