Winter mushroom walk, by Martin Holden

In January, noted Bay Area mycologist Robert Mackler led one of his popular fungal forays into the moist oak forests of Garber Park. A past president of the Mycological Society of San Francisco, Bob Mackler has been explaining the mysteries of mushrooms to since the 1970’s. Bounding through the wintery woods in his big boots and mushroom-dyed cap, he resembled a real-life Tom Bombadil. We were only a few paces into the park before we discovered our first fungus— a log festooned with Tukeytails (Trametes versicolor). Though not really edible, the leathery polypore is traditionally used to boost the immune system.

Previous walks had focused on the role of fungi in the changing ecosystem of the canyon. This time, we concentrated on the adaptations that allow particular fungi to live in the canyon’s varied environments. Some of the factors that we looked at were moisture, soil chemistry, and light. We also learned about the “lifestyle” specific to each fungus, whether parasitic,saprophytic, or mycorrhizal.

An abundant parasite in the canyon is the bracket fungus Ganoderma known as the “artist’s conk,” which grows on bay laurel trees. Brown on top, with a white underside which you can draw on (if you’re good at drawing upsidedown). Among the many saprophytes observed in the canyon was Marasimius quercophilous, which helps to decompose oak leaves. Without such “composting” fungi, the canyon would soon be filled to the brim with debris!

But it was the mycorrhizal mushrooms that generated the greatest interest. These fungi live in a symbiotic relationship with the roots of host trees, receiving sugars fromthem while helping them absorb vital nutrients from the soil. The oak trees in Garber Park have two important mycorrhizal partners— one delectable, and the other deadly.

The delectable one, of course, is the chanterelle (Cantharellus cibarius). This last winter was the best chanterelle season on record in coastal California, and though the season was nearing its end, it wasn’t long before walk participants had discovered handfuls of the golden, funnel-shaped fungi. Growing nearby was a fine example of the “death cap,” Amanita phalloides. Bob explained that this poisonous mushroom is a fairly recent introduction from Europe, apparently having been introduced in the vicinity of the Stanford campus about 40 years ago. Now, it’s responsible for most of the mushroom-related fatalities in California.

The competition for the cutest mushroom in Claremont Canyon ended in a tie. One contender was a tiny LBM (“little brown mushroom”), scarcely half an inch high, that grows in the moss on the bark of the big-leaf maples. The competition is the Candy Cap (Lactarius rubidus), a dusky red mushroom that smells just like maple syrup when dried. It can be used in cookies, or in one of Bob Mackler’s favorite recipes: Candy Cap creme brulée.