A message for those ­­interested in growing hemp in Iowa: Don’t do it, yet.

“Hemp is not legal in Iowa right now, though we expect it to be starting next year,” said Robin Pruisner, the state entomologist and ag security coordinator at the Iowa Department of Agriculture and Land Stewardship. “I’ve received calls from farmers who say they already bought their seed and are ready to go. That’s a problem.”

Pruisner shared the stage with Adam Ornawka, a farmer from Saskatchewan, Canada, during a breakout session of the Iowa Farm...