Peppermint and History

Dan Allosso

On Monday, Andrew Sullivan blogged at The Dish about “The Atomic Gardening Society.” After WWII, researchers explored ways to use the new discoveries of atomic energy to improve daily life. Atomic Energy Commission Chairman Lewis Strauss declared in 1954 that atomic energy would soon produce electricity that would be “too cheap to meter.” And, as Alexander Trevi records in an interview with Paige Johnson, which Sullivan highlights on his blog, national laboratories in the U.S. and U.S.S.R. developed gamma gardens, where they irradiated plants and seeds in an effort to improve flowers and agricultural crops.

One of the results of the gamma garden at New York’s Brookhaven National Laboratory was a disease-resistant strain of the peppermint plant, Mentha piperita. As Johnson says, commercial peppermint fields were increasingly suffering from Verticillium wilt, a fungal disease that reduces oil yields and ultimately kills the plants. Merritt J. Murray, a researcher for the A.M. Todd Company of Kalamazoo, developed two cultivars of Mitcham, the main commercial variety of peppermint, which were named “Todd’s Mitcham” and “Murray Mitcham.” Nearly all of the peppermint oil that finds its way into such products as chewing gum, toothpaste, mouthwash, and candy comes from these wilt-resistant plants.

It’s tempting to think of these scientific experiments of the 1950s to 1970s as the beginning of technical modifications to our food supply that have culminated in the genetically modified foods (GMOs) now causing public debate. But compared to current transgenic processes that manipulate plants and animals on a gene-by-gene basis, the process used by researchers in the gamma gardens was like stone tools versus scalpels. As Johnson notes, the “exact nature of the genetic changes that cause [Todd’s Mitcham] to be wilt-resistant remain unknown.” Scientists were literally shooting particles at plants and seeds, and then growing them to see what happened.

The other reason we can’t point to the gamma gardens as the beginning of GMOs, at least in peppermint, is that the Mentha piperita plants the researchers irradiated were already a hybrid that had been carefully nurtured by growers since at least the 1750s. Mentha piperita makes its first recorded appearance in Linnaeus’s Species Plantarum (1753). According to an 1851 history of the English town of Mitcham, titled Mitcham: Its Physic Gardeners and Medicinal Plants, the peppermint plant had been a principal product of the area’s medicinal gardens for about a hundred years. But the original, 1750s Mitcham peppermint itself was a genetically modified, sterile hybrid that could only be propagated by root cuttings.

The sterility of peppermint plants is due to the fact that they are a hybrid of two other Mentha species, water mint (M aquatica) and spearmint (M spicata). While this cross may have originally happened naturally, the resulting plants do not set seeds. They would not have been able to spread across the planet, without the active participation of mint farmers. And peppermint did spread across the globe. Brought to New England during the Colonial period, peppermint was grown, distilled, and sold through an elaborate web of early American commerce. Carried to upstate New York and then Ohio, Michigan, and Indiana by members of the mint-growing families, peppermint became a key crop in southern Michigan and northern Indiana, and later in the river valleys of Washington, Oregon, Idaho, and ultimately, India. Along the way, the peppermint plant has changed, due to the year-by-year choices of farmers deciding which roots to save, as well as through the efforts of specialists like Murray.

It’s interesting to speculate about what point we want to start calling a plant product like mint “genetically modified.” It’s also fascinating to think, as we’re brushing our teeth or drinking a cup of mint tea, that the plant whose flavor we’re tasting is basically the same genetic individual as the one planted by Michigan growers in the 1860s, or Massachusetts farmers in the 1810s, or Mitcham “physic gardeners” in the 1750s. For me it cuts to the heart of that interest in continuity and change that makes us historians.

Note: Dan may be slightly obsessed with this subject, as he’s currently writing a dissertation that looks at rural American history through the peppermint oil industry.