Toxicity of Morels and False Morels in the Pacific Northwest

Introduction

Mushroom edibility is not a simple yes or no. Even widely eaten species cause reactions in some people. Some foragers in Scandinavia and Eastern Europe eat Gyromitra esculenta after repeated boiling, but that does not reliably remove its toxin, and we do not recommend eating it. Reactions vary from person to person and with the amount eaten and how the mushroom was prepared.

This article gives an overview of the toxicity concerns for morels and similar mushrooms in the Pacific Northwest.

We still know little about the toxins in many mushrooms. Thorough cooking often lowers the chance of a reaction to a wild mushroom, but it does not rule one out. The first time you eat a species, eat a small amount and wait 24 hours before eating more. Eat only properly identified specimens, especially when less experienced foragers have contributed finds.

Morels

Morels are prized for their flavor, but they can cause illness. Raw or undercooked morels can cause gastrointestinal illness in some people, and the toxin responsible has not been identified. Thorough cooking often lowers the chance of a reaction but does not rule one out, so don’t eat them raw or partly cooked. (The hydrazine compounds discussed below are the toxins in Gyromitra, not in true morels.) For more on morels and alcohol, the neurologic syndrome, and the evidence behind these statements, see Are Morels Toxic When Consumed with Alcohol?

Between late March and mid-April 2023, a restaurant in Bozeman, Montana, was linked to an outbreak that made 51 people ill; 3 were hospitalized and 2 died. Both people who died had chronic underlying medical conditions, and neither clinical nor food testing identified a causative agent. Raw morels were more strongly associated with illness than partly cooked ones. DNA sequencing identified the morels as Morchella sextelata, and they had been cultivated and imported fresh from China (Demorest et al., CDC MMWR, 2024).

Gyromitra esculenta

Gyromitra esculenta contains gyromitrin, which the body converts to monomethylhydrazine. Poisoning typically begins with vomiting, abdominal pain, and diarrhea; in more severe cases it damages the liver, and in some cases it causes neurologic effects such as confusion, seizures, and coma. Monomethylhydrazine interferes with enzymes that depend on vitamin B6 (Benjamin). Cooking drives off much of the toxin, but the vapor is itself poisonous, and preparation methods do not reliably make the mushroom safe. In the NAMA case registry’s roughly 2,000 reports from more than 30 years, 27 people were reported sick from G. esculenta, 3 of them fatally (Beug et al.). In one 1967 report of 513 cases, 14% were fatal (Benjamin). Because the registry depends on voluntary reports, these counts are minimums.

Verpa bohemica

Sources disagree about Verpa bohemica, the early morel. Mushrooms of Cascadia (Siegel & Schwarz) lists it as edible. Arora reports severe stomach cramps and loss of coordination, especially after large amounts eaten on several days in a row, and a 2020 toxicology review (Lagrange & Vernoux) recommends against eating it. Davoli and Sitta describe a long tradition of eating it in Emilia-Romagna, in Northern Italy, where it is sold officially, and conclude that it shares the edibility status of true morels; they note that most North American texts list it as suspect or toxic. See the Verpa bohemica page for more.

Helvella vespertina

Mushrooms of Cascadia (Siegel & Schwarz) lists the western black elfin saddle, Helvella vespertina, as edible if cooked well. Raw or undercooked Helvella have caused gastric upset, and the toxins responsible are not well understood, so don’t eat them raw. See the Helvella page.

Hypomyces cervinigenus is a parasitic mold that grows only on Helvella, coating them in whitish fuzz that slowly turns pink (Kuo). Kuo gives no information on its edibility, so discard any fuzzy or discolored specimen.

Conclusion

Edibility and toxicity depend on the species, how it is prepared, how much is eaten, and individual sensitivity, and research on many species is thin. Cooking, drying, and parboiling can lower the risk of a reaction in some species but do not eliminate it. Serious mushroom poisonings are rare, and the routine risks of wild mushrooms are worth weighing against those of common foodborne pathogens such as norovirus, Salmonella, Listeria, and E. coli. Identify every mushroom you eat with care.

References Cited

1. Beug, M., M. Shaw, and K.W. Cochran. “Thirty years plus of mushroom poisoning: summary of the approximately 2,000 reports in the NAMA case registry.” McIlvainea 16(2): 47–68 (2006). Read more.
2. Benjamin, D. “Gyromitrin poisoning: more questions than answers.” Fungi 13(1), Spring 2020. Read more.
3. Horowitz, K. M., Kong, E. L., & Horowitz, B. Z. “Gyromitra Mushroom Toxicity.” In StatPearls [Internet]. StatPearls Publishing. Read more.
4. Lagrange E, Vernoux J-P. “Warning on False or True Morels and Button Mushrooms with Potential Toxicity Linked to Hydrazinic Toxins: An Update.” Toxins. 2020; 12(8):482. Read more.
5. Davoli, P., & Sitta, N. “Early morels and little friars, or a short essay on the edibility of Verpa bohemica.” Fungi 8(1): 4–9 (2015). Read more.
6. Kuo, M. (2023). “Hypomyces cervinigenus.” MushroomExpert.Com. Read more.
7. Demorest, H., Hinnenkamp, R., Cook-Shimanek, M., et al. “Outbreak Linked to Morel Mushroom Exposure — Montana, 2023.” MMWR Morb Mortal Wkly Rep 2024;73:219–224. Read more.
8. Ebelt, J., & Whaley, H. (2023, July 19). DPHHS and GCCHD Provide Final Summary on Foodborne Outbreak Linked to Morel Mushrooms. Montana Department of Public Health and Human Services. Read more

Sources: Mushrooms of Cascadia (Siegel & Schwarz, 2024); MycoMatch (© Ian Gibson), a compilation of published descriptions through which most other field-guide authors named here are quoted; the references listed above, including the CDC MMWR report on the 2023 Montana outbreak and the NAMA case registry summary (Beug et al.).