Spring is the most beautiful time of year when the earth wakes up right before our eyes. Leaves and flowers are popping. And our favorite tasty morsels, mushrooms, are also showing up, including morels.
You might have heard some old wives’ tales about morel emergence in the past. “When oak leaves are the size of a squirrel’s ears”, “when may apple leaves open up like umbrellas”, etc. What indicators can we rely on that are more scientific and measurable to help predict when it is time to go out ‘shroom hunting?
Soil temperatures can serve as a good indicator for morel emergence. Professor Jeanee D. Mihail from the University of Missouri found that the best predictor for morel popping in Missouri was the accumulation of degree days. “Soil warming of 410 degrees F over a twenty-day interval is a very useful predictor for the first appearance of morels in the Missouri region.”
Of course, soil warming is not the only factor that can determine the likelihood of morel emergence. Winter weather, chilling duration, and the soil temperatures/warming in the spring are important factors to consider. Morels can start popping up when soil temperatures reach around 50-60 degrees F, and most of Iowa has 4” soil temperatures hovering right around 50 degrees F now in mid-April.
Degree days are calculated as the accumulated days experiencing temperatures above a specified threshold for a specified timeframe. Using a growing degree day (GDD) air temperature base of 40 degrees F, a weather station near Ames, Iowa, recorded an accumulation of 400 degree days by April 1st. 
Another great way to estimate when morels might be popping is to track reported findings of morels near you. There are a couple different ways you might go about this. The Great Morel has a map that tracks sightings that anyone can view. Also, if you’re on Facebook, there is a group called Iowa Morel Report that posts weekly updates of where morels have been found in the state by county.
Source: Jeanne D. Mihail (2014) Is It Time for Morels Yet?, McIlvainea 23 (53–60): http://www.namyco.org/publications/mcilvainea/v23/time_for_morels.html
Written by: Madelynn Wuestenberg (Climate Extension Specialist) and Chelsea Harbach (Plant Disease Diagnostic Specialist)
Chelsea Harbach Plant Disease Diagnostician
Chelsea Harbach is the plant disease diagnostician in the Plant & Insect Diagnostic Clinic. She is passionate about plant pathology and helping people, which makes a career as a literal plant doctor a perfect fit.
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