This fall, for the first time since 1970, farmers throughout the United States were set to harvest federally legal hemp. From New York to Kansas to Oregon, they had applied for licenses to plant nearly half-a-million acres of the non-psychoactive cannabis. Farmers had purchased seeds and tended fields throughout the summer. But toward the end of the growing season, many of them realized that their plants weren’t turning out as expected — and at worst, that their entire crop would have to be destroyed.

While the corn and soybeans had, as usual, sprouted all at once and grown to a uniform size, new hemp plants tended to grow on different schedules, to different heights. Sometimes there weren’t that many hemp plants at all, because a relatively small percentage of the seeds had sprouted. The most dramatic surprise, however, was to farmers who had intended to plant hemp with a high concentration of the chemical compound known as CBD — a potentially lucrative prospect given the ingredient’s addition to everything from lattes to pet treats — and instead ended up growing what the federal government classifies as marijuana.

All cannabis plants, including hemp, have some amount of the psychoactive chemical compound THC. Cannabis sold legally as marijuana may have as much as 20% THC on a dry-weight basis, while farmers growing hemp for textiles, food, or CBD are required by law to meet a much lower limit of 0.3%. Neither a 0.3% THC cannabis plant nor a 0.4% THC cannabis plant will get you any higher than smoking grass from your lawn, but in the eyes of the law, that tiny tenth of a percent makes all the difference.

To comply with federal rules, states must ensure the “disposal” of a hemp crop that tests over the 0.3% limit, a process that usually involves plowing it down or burning it on-site. A draft of new hemp-growing guidelines proposed by the USDA, the first such guidelines from the federal government, establishes a margin of error for meeting the THC limit, but is strict about the consequences of failing the test. If the rules go into effect as written, farmers with what the industry calls “hot” crops that exceed the 0.3% limit will be responsible for paying an estimated $200 per acre to destroy their own crops, on top of losing the commercial value of the plants. This is true even if the grower is operating in a state that has legalized recreational marijuana, which requires a different type of license.

The problem is that while the race to plant hemp has taken off at a sprint, the race to study hemp is a marathon that is just getting started.

Almost 90 hemp sites in Colorado have tested “hot” this year, the state department of agriculture told OneZero. The Oregon Department of Agriculture said eight hemp sites have tipped the limit, while Hawaii reportedly destroyed more than half of its hemp crops because of high THC content. Meanwhile, the advocacy organization Vote Hemp estimates that only 50% to 60% of the hemp planted this year will actually be harvested, due to what it calls “crop failure, non-compliant crops, and other factors.”

The problem is that while the race to plant hemp has taken off at a sprint, with 17,000 farmers applying for licenses this year alone, the race to study hemp, which has also been essentially banned wherever the crop was illegal, is a marathon that is just getting started. Published research, seed certification processes, and understanding of the cannabis plant’s genome are all lagging behind the plant’s rapid commercial adoption.

At a time when the genetics of other crops are so well developed that corn farmers can choose between certified seed that will be ready to harvest in 79 days, 84 days, or 89 days, hemp farmers have no way to know for sure how much THC any variety of cannabis plant will produce under a variety of conditions — not to mention whether they’re buying high-quality seed at all. As Michael Bowman, the co-founder of a public benefit corporation that partners with small hemp growers, puts it, “it’s been a crap shoot.”