It’s that time of year when you see cars and pickups parked in odd places along the road. When people bearing bread sacks full of gray lumps are mum about where they’ve been. When sales of those lumps show up online for huge sums. Yes, it’s time for hunting morel mushrooms.

While the delicacies appear in almost every state and in other countries, different species grow in different areas. In Iowa, the gray morels come out first, followed by the yellow ones. The largest ones, Morchella crassipes,...