Top Ten Poisonous Mushrooms of California

Concerns about poisonous mushrooms outweigh the love of mushrooms in the general populace, and in a few species these concerns are valid. To go into the woods to find mushrooms for food is noble, but to know mushrooms that are poisonous is to be safe. People should be careful, and get to know poisonous species before they start to eat mushrooms they gather

themselves from the wild. Plus these can be interesting mushrooms to find: some are common, some are beautiful.

If you are planning on finding mushrooms for food in the wild, as an extra challenge for the season this year and for safety’s sake, try to find and ID these also. Just make sure you don’t eat them!

For ID confirmation, come to one of FFSC's events; join our Google Group, or try other resources where experts can be found. (See our FAQs for links.)

This list was compiled with help from Mike Beug, Professor Emeritus of Evergreen State College, Olympia WA. The Toxicology Chair of the North American Mycological Society, Mike has been compiling stats on mushroom poisonings for years, and was very helpful in creating this list. The list is the top ten weighted by the seriousness of the poisoning along with the number of poisoning cases from the western US each year.

1. The Death Cap — Amanita phalloides

The Death Cap is the most deadly of mushroom species, accounting for more deaths that any other. It contains amanita toxins which block cells’ ability to function, and then destroys the liver. A. phalloides causes serious illness, liver damage or failure, and death. Each year a few cases of this occur in California, usually from people moving here that were used to eating edible Amanitas at home.

Identity can be determined by a thick base with a volval sack, off-white grey to grey-green cap, and bright white stipe, gills, and partial veil. Usually found with live oak in California, there are rare sightings with other oaks reported. Common in the Bay Area and south, it is slowly moving out to other areas of California, and can be found from Mendocino to Los Angeles, and east through the central valley.

2. The Destroying Angel — Amanita ocreata

A mushroom as deadly as A. phalloides, also containing the deadly amanita toxins. This one causes fewer deaths, because it seems to be eaten less often. Perhaps because while A. phalloides is found early to mid-season, this one is usually found mid to late-season. Still a serious concern, and can be confused with the fairly popular local edible Amanita velosa, which shares the same season and habitat.

This species has a similar base and stipe to A. phalloides, with the thick base, and volva, and the same bright white stipe, gills, and thin partial veil. This species differs in that the cap is usually off-white, sometimes with a tan central disc, and rarely with pink colors in the tan. The partial veil on the stipe of this one is so thin, it often disappears, something to keep in mind for a careful ID.

3. Green Spored Parasol — Chlorophyllum molybdites

The most common cause for poisoning cases in the USA, but this is more true in the midwest and east than for California. Causes severe gastrointestinal distress in most people, and enough to cause some to end up in the hospital. Usually confused with the edible Shaggy Parasol (Chlorophyllum rachodes/brunneum) which it can look very similar, except the poisonous species has green spores, and the edible species have white spores. Found in grassy places, and landscaping.

4. The Fly Agaric — Amanita muscaria and A. pantherina

Amanita pantherina. © Darvin DeShazer (from mushroomobserver.org)

Amanita muscaria subsp. flavivolvata. © Darvin DeShazer (from mushroomobserver.org)

A tie for fourth place, these two species have similar effects on people, and cause similar numbers of cases in the west. These contain muscimol and ibotenic acid which produce a number of effects in people, from severe sickness to fever, sweating, and delirium. Along with being poisonous, it is also one of the most popular mushrooms from the wild. If someone asks me to ID this fantastic mushroom they saw hiking, it is usually the A. muscaria. These are very common species in California, found among pine and fir trees.

5. The Western Jack-o-Lantern — Omphalotus olivascens

This mushroom causes gastrointestinal upset. It’s a “wishful thinking” poisoning: if compared for long enough with a chanterelle picture, "maybe it will be OK to eat!"

Although this mushroom isn’t really that close to the chanterelle, they do share orangish colors, and a vaguely vase-shaped body form. The Jack-o-Lantern is different in that it often grows clustered, on wood, with brown-green colors, and thick, true gills in comparison to the vein-like false gills of the chanterelle.

6. The Deadly Galerina — Galerina marginata (autumnalis)

A small brown mushroom, this one also contains the amanita toxins that are found in A. phalloides, and can be a quite serious and deadly mushroom if eaten. It is rarely eaten, and almost never confused with any mushrooms used for food, but it could be confused with Psilocybin mushrooms if those were desired. Found on wood, it is small, brown, and usually with a fibrous veil near the top of the stipe, that is brown with adherent spores.

7. The False Morel — Gyromitra esculenta

A spring-time ascomycete that shares the same season and habitat with the popular edible Morels. This is a confusing mushroom in term of edibility: it was called a choice edible for years, but it contains poisons that get processed into monomethylhydrazine in the body. The tolerance for this chemical in the body is extremely variable, going from nothing to kidney failure. This is the cause of many serious poisonings in the midwest, but poisonings are rare in California.

8. Psilocybin mushrooms — Psilocybe coprophila / cyanescens and others

This is a collection of species that contain the chemicals psilocybin and psilocin, which are hallucinogens. They cause confusion and delirium in people, and send a few to the hospital each year. These are more a concern for small children, where their low body weight makes the effect stronger, and at least one case of death of a small child is attributed to these. Small brown mushrooms with deep purple-brown to black spores, they usually stain blue when bruised. Depending on species they grow on either wood chips or dung.

9. False puffballs — Scleroderma polyrhizum / cepa / areolatum

These are similar to puffballs, growing on the ground, with spores developing inside. They differ from other puffballs with a thick yellow-brown skin, a yellowish inside when young, and spores that are purple-black when mature. Other puffballs develop deep brown spores. They have caused kidney/liver failure in pigs and dogs, but this hasn’t been seen in people yet. Poisonings of these are rare in the US, but more common in California, perhaps due to the popularity of puffballs for the table here. Make sure you can ID Scleroderma before eating any puffballs.

10. Poison Pax — Paxillus involutus

A species that is sometimes eaten in Europe, but it contains poisons that result in kidney failure if they build up in your system. There are some deaths attributed to the mushroom, but poisonings seem to be rare in California, perhaps because it is such a drab and fairly ugly mushroom in our area. This can be identified by its vase shape, long decurrent gills, and brown velvety cap.

And wait, there’s more... Mike Beug actually put a surprise species higher on the list here —

Morels! — Morchella elata / esculenta

Although these are a top ten edible, when raw and undercooked they account for a number of poisoning cases in California. I’ve pushed this to an afterword to point out other species and keep the top ten format, but people should keep this in mind when eating morels.