Thanksgiving tables across America usually tend to look the same: the gigantic roasted turkey, the mashed potatoes, some sort of vegetable masquerading as a desert, and, of course, cranberry sauce. Depending on family traditions, that sugary smooshy stuff is either made from scratch with whole cranberries or plopped out of a can. But canned or fresh, there is a very high likelihood that your cranberries come with a less-than-sweet past.

Ocean Spray is the world’s leading supplier of cranberry-related products, controlling 75% of cranberry farms in the US and Canada since 1930. This includes their cranberry juice, fresh cranberries, craisins (which were created as an Ocean-Spray marketing ploy, by the way), cranberry sauce, and a whole smattering of other products. Ocean Spray sells 20% of their fresh cranberries during the week leading up to Thanksgiving—a whopping 80 million pounds of them.

The cheerful nature of Ocean Spray’s advertisements leads you to believe that cranberry farming is clean, natural, and safe: the cranberries sitting in lush fields of water, sparkling in the sunlight, and farmers talking about how many generations they have been sitting in a cranberry bog, just to bring fruit to your family’s table. Unfortunately, that’s not the full story.

Cranberries are grown in bogs primarily in the northern part of the US in soft, marshy ground with acid-peat soil. They’re hard to harvest on the vines they grow on, so instead, the bogs are flooded at harvest time, water reels pull them off the vine, and the cranberries float to the top, allowing them to be collected and sent off to market. Those images you see of farmers in waders, up to their chests in water with cranberries floating all around them? Totally accurate.

Cranberries aren’t easy to grow, and Ocean Spray figured that out quickly. In the 1950s, they began spraying bogs with aminotriazole, a chlorophyll inhibitor that had been known to cause growths in lab rats, as a means to clear the bogs of grasses, cat-tails, and other weeds. Farmers were only permitted to use aminotriazole one week after the November harvest so that it had rubbed off the finished fruit in time for Thanksgiving. But in 1959, word got out right before Thanksgiving that a small barrel of cranberries harvested in the Pacific Northwest had tested positive for the herbicide.