It’s rare to happen upon someone strolling through a cornfield—and for good reason. If you’ve never walked through one, it is not a pleasant experience. Tightly packed rows of stalks almost 10 feet tall create an almost full canopy overhead. Underneath, row widths much narrower than your hips include sharp, jutting corn-leaf edges that inflict papercut-like nicks to any exposed skin as you brush past. And if you’re there during the tasseling and silking stages, your skin may break out in a rash from the falling pollen. Appropriate attire for field scientists in cornfields includes boots, long pants, and sleeves, a sturdy hat, and glasses to protect your eyes from being cut by the leaves. In other words, anyone making the trek into a cornfield is going with purpose, whether to sample insects or surreptitiously grow marijuana.

When the person approaching saw us, our field gear, and our surprise, they quickly disappeared back into the dense sea of green stalks. While we never saw them (or their marijuana) again, it became clear that this was not an isolated incident. Almost every corn grower I spoke to that summer had a tale of discovering marijuana in their cornfields at harvest time. Which led me to ask: what is it about the nation’s largest crop that has made it so attractive to marijuana growers in recent years?

The answer: Growing marijuana has become possible and desirable, not to mention nearly untraceable, thanks to the very innovations that created industrial-scale, precision agriculture in the first place.