What do rocket fuel and this fungus have in common? No, it has nothing to do with the third line in the lyrics of Elton John’s and Bernie Taupin’s Rocket Man.
However, it does have something to do with the inevitable question that is asked of mycologists leading tours: “Can I eat it?”. As an aside, I know of one mycologist who occasionally goes on walks with ornithologists (bird scientists) and asks the same question. Anyway, despite the epithet esculenta (meaning “edible”), it is not advisable to ingest false morels. Dr. Tom Volk answers the question of why not and explains the rocket fuel association in his page on Gyromitra esculenta:
Eight to ten species of Gyromitra exist on the North American continent and about two or three in Europe. Although they are much sought after in Europe as an edible species (Gyromitra esculenta), 2 to 4 per cent of all mushroom fatalities are associated with them. It is not clear whether the same species occurs in North America, although we call one species here by that name. The active ingredient is called gyromitrin (N-methyl-N-formylhydrazine), which is metabolized to monomethylhydrazine (rocket fuel!) in the body. Eaten raw, most of the Gyromitra spp. are quite poisonous. In an attempt to prevent poisoning caused by ingesting the mushrooms, they are usually parboiled to evaporate the gyromitrin, which gives off a chocolaty odor. The process is usually repeated twice, with the water being discarded each time. However, the volatile chemical can be inhaled through the nose, and enough can be left in the mushrooms to cause illness when eaten. So just standing near the boiling pot of mushrooms can cause problems, and there is still the possibility of poisoning by ingestion.
(Another aside: some of you may know Dr. Volk had cancer and then underwent a heart transplant after the radiation therapy damaged his heart. In February 2018, Tom did a TEDx talk about his journey: A Change of Heart: My Transplant Experience)
It is absolutely worth reading Tom’s page about Gyromitra if you are considering eating these, but I’ll summarize: there is some taxonomic doubt as to whether the Gyromitra esculenta of North America (or all of North America) is the same species as in Europe. There is also apparently variation among populations of Gyromitra esculenta in North America in terms of toxicity, which is seemingly the case for other species of Gyromitra as well. Tom’s conclusion is that these have a significant amount of risk, if being consumed.
Weird and Wonderful Wild Mushrooms has a write-up about Gyromitra esculenta and Gyromitra gigas: Two False Morels. Two other excellent resources (as always) are Mykoweb: Gyromitra esculenta and Michael Kuo’s MushroomExpert.com: Gyromitra esculenta.