Glyphosate

Glyphosate emerged from an unlikely source—a failed water softening compound—to become the world's most widely used herbicide. Its discovery at Monsanto exemplifies how scientific detours often yield transformative destinations, and how a single molecule can reshape global agriculture.

The adjacent possible began with phosphonic acids. In the late 1960s, Monsanto's Organic Division had synthesized compounds intended to chelate minerals in hard water—water softeners, not weed killers. Two of these phosphonic acid compounds showed surprising herbicidal activity when tested by Dr. Phil Hamm's screening program. The chemistry intrigued John Franz, an organic chemist who had recently transferred to Monsanto's new Agricultural Division.

Franz took over the research in 1969 with an incorrect but productive hypothesis. He theorized that the phosphonic acids acted as 'proherbicides'—compounds that plants would metabolize into the actual active ingredient. This led him to synthesize possible metabolites. In 1970, the third compound he created—N-(phosphonomethyl)glycine, or glyphosate—proved spectacularly effective at killing plants.

Glyphosate worked unlike any herbicide before it. The molecule inhibits EPSP synthase, an enzyme in the shikimate pathway that plants use to synthesize aromatic amino acids essential for protein production. Animals lack this pathway entirely, suggesting (controversially, as it turned out) a favorable safety profile. More practically, glyphosate killed almost all plants—grasses, broadleaves, perennials—making it a true broad-spectrum herbicide.

Monsanto began commercial development in 1973 and introduced glyphosate to the market in 1974 under the trade name Roundup. Initial applications focused on industrial vegetation control—clearing railways, roadsides, and utility rights-of-way. But glyphosate's potential for agriculture awaited another invention: herbicide-resistant crops.

The cascade transformed modern farming. In 1996, Monsanto introduced Roundup Ready soybeans—genetically engineered to survive glyphosate treatment. Farmers could now spray entire fields, killing weeds while leaving crops unharmed. Roundup Ready corn, cotton, canola, and sugar beets followed. By 2014, glyphosate usage exceeded 826 million kilograms globally—a 100-fold increase since 1974. The herbicide enabled no-till farming, reducing soil erosion while increasing yields.

Franz received the National Medal of Technology in 1987 and induction into the Inventors Hall of Fame in 2007—far greater recognition than the $5 Monsanto paid him for the original patent. Farm Chemicals magazine named Roundup one of the 'Top 10 Products That Changed the Face of Agriculture.' Whether that change was entirely beneficial remains contested, as glyphosate's environmental and health effects sparked decades of scientific and legal controversy.