Mushrooms in the forest


Each year, winter rains bring a variety of mushrooms out at Midpen preserves. The multitude of fungi are amazing, but some are deadly poisonous. Picking and eating wild mushrooms can kill you! Mushroom collecting is not allowed anywhere in Midpeninsula Regional Open Space District. Please leave mushrooms alone for other visitors to see and for the safety of you and your family.

Ecologically Sensitive Mushroom Finding Tips

Though dreary skies can sometimes put a damper on human spirits, constant moisture creates a paradise for mushrooms and other fungi. If you are a fungus fan, the rainy season is the best time to go on an ecologically sensitive mushroom hunt. Here are some tips to help you find some cool new mushrooms while out on the trail (keep in mind that collecting mushrooms in Midpen preserves is illegal! Please take only pictures):

  1. Learn about trees! This may seem counterintuitive, but certain mushroom species will only grow in relationship with certain species of trees. If you learn to identify these trees, then finding new varieties of mushrooms becomes much easier. Some important mushroom host tree species to know are Western hemlocks (Tsuga heterophylla), coast live oaks (Quercus agrifolia), Douglas fir (Pseudotsuga menziesii), and pine tree species (Pinus spp.).
  2. Take a close look at rotten logs! Look at the log from every angle. Sometimes you have to get really close to see the tiny fungi that live in the cracks of decomposing wood.
  3. Take it slow! Many miniscule and inconspicuous fungi will be missed by a hurried searcher. You often make the coolest observations when you take the time to really look.
  4. Persistence! Often the most frustrating thing about fungi is that they are unpredictable. You may venture out on a misty morning, expecting to see some cool exotic coral fungus, or a bright orange jelly ear and spot none. However, as you continue to spend time enjoying the brilliant company of fungi, you will soon intuitively learn much about how they exist – their patterns and habits.
Tiny white mushrooms on the forest floor

Toxic Mushrooms

The Bay Area is home to two of the world’s most toxic mushrooms – Amanita phalloides (the death cap) and Amanita ocreata (the western destroying angel). Both grow near oak trees and contain lethal toxins.

The Death Cap (Amanita Phalloides)

The death cap is a medium to large mushroom that typically has a greenish-gray cap, white gills, a white ring around the stem, and a large white sac at the base of the stem. It fruits early in the fall, usually right after the first rains. Though the death cap is mainly associated with oak trees, it has been found growing with other hardwoods. It was accidentally introduced to North America on the roots of European cork oaks, and is now slowly colonizing the West Coast.

photo of a cluster of death cap mushrooms

The Western Destroying Angel (Amanita Ocreata)

Amanita ocreata (the western destroying angel) is a medium to large mushroom that usually has a creamy white cap, white gills, a white ring around the stem that disappears with age and a thin white sac at the base. It fruits from late winter into spring, and is associated exclusively with oaks. Unlike the death cap, it is a native California mushroom.

photo of the Western Destroying Angel

 Both of these species contain amatoxins, a group of molecules that inhibit cellular metabolism in many animals. In mammals, the liver and kidneys are typically the first organs affected after ingestion. Symptoms don’t usually appear until about 12 hours after consumption, beginning as severe gastrointestinal distress and progressing to liver and renal failure if treatment is not sought immediately.

While these two species are responsible for most cases of mushroom poisonings in California, deadly amatoxins can be found in Galerina and Lepiota species as well, both of which occur in the Bay Area.  

Pet owners are encouraged to keep their animals under close watch during the winter months, and contact a veterinarian immediately if you suspect your pet has eaten a toxic mushroom.



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