A mushroom, technically speaking, is the fleshy, spore-bearing fruiting body of a fungus. Although that doesn't sound terribly appetizing, edible mushrooms represent a low-calorie, beneficial food source that can add value ﻿-- and flavor -- to your diet. They are a good source of protein, vitamin B, vitamin D and the essential minerals selenium, copper and potassium. One ounce of mushrooms amounts to only about 20 calories.

Understanding the many parts of a mushroom can help you distinguish the edible varieties from the poisonous ones. Many have a cap (curved top) with gills on the underside. If they do not have gills (feathery membranes), they have pores (small holes) in the cap; both are used for spore reproduction. The stipes (stems) are stalks that support the cap.

Edible: Oysters (Pleurotus) are gilled mushrooms, also known as abalone or tree mushrooms.
Edible: Oysters (Pleurotus) are gilled mushrooms, also known as abalone or tree mushrooms. (Photo by Mike Davis/University of California)

Some mushrooms have rings and cups. The ring is a fleshy ridge that extends around the stem. Some varieties have stems that rise from the cup (also called the volva), usually at soil level or underground. Amanita, the most deadly genus of mushrooms, has rings and cups. Although there are edible varieties of Amanita, they should be avoided unless you are an experienced, skilled —‰'shroomer".

Mushrooms "pop up" in order to spread spores for reproduction, then are either eaten or rot away. The mycelium, an underground network of threadlike cells, is the central part of the fungi; it can survive for many years. Most of the mushrooms we encounter grow on or above the soil or on nutrient sources such as the bark or decaying roots of trees. You may see them sprouting up out of the mulched areas of your landscape, your compost pile or even on an old section of fence.


There are thousands of varieties of mushrooms; according to the Sonoma Mycological Association, 171 edible varieties can be found in Northern California.

Some consider the "standard" definition of the term mushroom as describing those fungi that have a stem, a cap and gills or pores on the cap's underside. However, more generally (and in this article), the term is used in its broader sense to describe varieties with fleshy fruiting bodies, leathery/woody fruiting bodies and those with or without stems.

Although several varieties are toxic, only a few are truly deadly. Symptoms from ingesting toxic species include severe cramping, vomiting, diarrhea, gastrointestinal and stomach pain. (See details on several varieties in the accompanying list.)

With more of us wanting to get in touch with where our food comes from and with the "slow food" movement pointing to the advantages of "growing your own," foraging is becoming ever more popular. Although foraging can be a fun, rewarding endeavor, it is extremely important to know the exact variety of any mushroom you encounter before you take a chance on eating it. Learning about the mushrooms that pop up in your backyard is also important for keeping your children and pets safe.

We have many mycologists (those who study fungi) right here in the Bay Area. If you are interested in learning more, in growing your own mushrooms or venturing out on a hunting expedition, contact one of these groups:

  • Bay Area Mycological Society (BAMS): http://bayareamushrooms.org

  • Mycological Society of San Francisco (MSSF): www.mssf.org

  • Fungus Federation of Santa Cruz (FFSC): http://fungusfed.org

  • Sonoma County Mycological Association (SOMA): www.somamushrooms.org

    Rebecca Jepsen is a Santa Clara County Master Gardener. Also contributing to this article were Master Gardeners Jim Maley and Marilyn Diamond. The Santa Clara County Master Gardener Program is a UC Cooperative Extension volunteer organization dedicated to providing research-based gardening information to home gardeners. If you a question, call the UC Cooperative Extension Master Gardener hotline in San Jose at 408-282-3105 from 9:30 a.m. to 12:30 p.m. Mondays through Fridays. Visit the Master Gardeners website, www.mastergardeners.org.

    10 mushroom varieties

    Death Caps (Amanita phalloides) account for about 50 percent of all deaths caused by mushrooms worldwide. They have large sporeless caps that can be 2 to 6 inches wide and range in color from pale yellow to olive green. Caps are covered by a thin white veil. Stems and gills usually are white and have a ring and cup (you may have to dig into the soil a bit to see these). The Death Cap is often mistaken for the edible Paddy Straw mushroom (Volvariella volvacea), which has pinkish brown gills. Fortunately, the Death Cap is seldom found in urban gardens, but is abundant in the Santa Cruz Mountains and near the coast, where it grows near coast live oak and cork trees. Ingesting it can cause liver and kidney damage and, as the name implies, can be fatal.

    Destroying Angel (Amanita ocreata) grows on or near a variety of oak trees. The cap may be white or ocher, and it often has a brownish center. The stem and gills are white. Ingestion can cause jaundice, delirium, seizures, coma and death.
    Green-spored Parasol (Chlorophylium molybdites) is responsible for the most common cause of serious, but nonfatal, mushroom poisoning in North America. It is a large, attractive, creamy-white species often found in lawns.
    Jack O'Lantern (Omphalotus olivascens) has orange flesh, rather than white, and it often a greenish tinge and deep gills. It is commonly mistaken for the edible Golden Chanterelle. Ingestion causes serious gastrointestinal symptoms, sometimes lasting several days.


    (These varieties have a symbiotic relationship with living trees)
    Porcini (Boletus edulis grandedulis) is a common species in California, first identified in 2007. The porcinis have convex caps that flatten out with age. They are generally reddish-brown, fading to white near the edges. Stems can grow up to 10 inches tall and nearly 3 inches thick, and they tend to bulge in the middle. They can grow extremely large; some specimens have weighed in at more than 2 pounds! Since Porcinis develop symbiotic relationships with living trees, they are found only by foraging. They are not currently cultivated.
    Chanterelles (Cantharellus cibarius) generally are orange, golden or black and are funnel-shaped. They have an aroma similar to apricots and a peppery taste. They have smooth caps and long, gill-like ridges running almost the whole way down the stem. One of the most common local varieties is found under oak trees.
    Shaggy mane (Coprinus comatus) commonly grows on lawns or along gravel roads. They first emerge as white cylinders with bell-shaped caps that open out. The caps are covered with scales; they are initially white, turning pink and then black. They are best eaten when young. They are very unusual, in that they turn black and almost completely dissolve within a matter of hours after being harvested.


    (These varieties thrive in a created, controlled environment with a food source).
    Button (Agaricus bisporus) is the most commonly and widely cultivated variety of mushroom in the world. Young specimens have closed caps, and they are pale white to light brown in color. Immature versions with darker flesh are marketed as brown, cremini or baby portobellos. Mature specimens have slightly opened caps and are known as the prized portobellos.
    Oysters (Pleurotus) are gilled mushrooms, also known as abalone or tree mushrooms. They are widely cultivated and eaten throughout the world. Cylindrical in shape, they are often laterally attached to their host without a stem. They are generally creamy white to light brown, and they can grow quite large. They can appear to be gowning in a stacked fashion on a tree. Boxed kits are available that allow you to grow your own.
    Shiitakes (Lentinula edodes) are featured in many Asian cuisines (fresh and dried) and are native to East Asia. They are often widely considered to have medicinal properties and have been harvested for more than 2,000 years. They generally have golden to maroon-brown or blackish caps with gemlike dots around the rim. Many mushroom aficionados successfully grow their own shiitakes with specialty logs, spawn and lots of patience.
    -- Rebecca Jepsen