The mysterious mushroom, sign of a healthy garden


A wood-decaying polypore mushroom on a fallen tulip poplar tree. (Adrian Higgins/The Washington Post/ADRIAN HIGGINS/THE WASHINGTON POST)
Adrian Higgins
Gardening columnist October 12, 2011

We are in the midst of mushroom madness, the likes of which we haven’t seen in years. This is thanks to a soaking September. Gardeners, who are by nature controlling, just have to go with the flow. You never know when — or where — a mushroom might pop up.

My veggie garden has a wood-chip patio, from which erupted a robust, classically formed mushroom with a cap that was a ruddy-brown. I pulled it to examine the thing: the stem was white and stout, and the gills beneath the cap an ivory yellow and distinctively branched. I’m fairly sure this is a fungus called the burgundy cap, and the guides say that it tastes good when young. The trouble is, when it comes to mushroom foraging, “fairly sure” doesn’t hack it.

Adrian Higgins has been writing about the intersection of gardening and life for more than 25 years, and joined the Post in 1994. He is the author of several books, including the "Washington Post Garden Book" and "Chanticleer, a Pleasure Garden." View Archive

The common and tasty meadow agaricus is remarkably similar to the toxic yellowing agaricus. Amanita virosa looks pristine white and delicious, to its victims it is the destroying angel.

Mushrooms, or the darker term toadstools, carry ominous connotations in our mycophobic culture. They are associated with poison and hallucination, the occult, with fairies and the underworld. There is the idea that a toadstool is killing our plants.

A few fungal types do harm garden plants, notably the honey fungus. It is one of the bad guys that feed off living trees (unusually drought stressed). More species feed off wood that is already dead. Here’s the thing about the mushroom. It is merely the fruiting body of a much larger and permanent organism that lives beneath the soil. It is akin to the flower of a plant, dispersing its seed. I like to think of a mushroom as the dorsal fin of some great whale that lives in the depths. It flashes, it is gone, the leviathan passes from our consciousness, but it is still there.

This awareness, or lack of it, is changing. The interest in organic gardening has stirred a deeper knowledge of soil life. We know now that most fungi live in partnership with our garden plants in a veiled symbiosis. The myriad threadlike strands, the mycelia, of each organism effectively extend the root system of trees, shrubs and virtually all other plants. The plants feed the fungi sugars, giving them the energy to produce mushrooms. The fungi deliver nitrogen and other nutritious elements to the plants.

Although the strands are fine, they can form enormous webs. “It’s a loose network of filaments that can extend for miles,” says James Nardi, a biologist at the University of Illinois and author of “Life in the Soil.”

About 5,000 species of fungi grow on the roots of approximately 2,000 species of coniferous and flowering trees, Nardi writes. Another 130 fungal species tap into the roots, threading their strands between cell walls.

Next time you look at a mushroom, don’t assume it’s hurting your trees or lawn. It may kill you, but it’s doing your oaks a lot of good. And because we only see a fraction of the whole organism, kicking it over isn’t going to do anything. The creature, though, puts an enormous amount of energy into forming a mushroom. It seems unfair to destroy it casually.

Compost gurus like to smell, touch and perceive the finished product, and look for those little white fungal threads as a mark of a compost teeming not just with good fungi but bacteria as well. Indeed, scientists have discovered that fungal partners of plant roots also contain beneficial bacteria. “It’s a relationship between the bacterial, fungal and plant kingdoms," Nardi says. So it’s a relationship with us as well, and mushrooms are a wonderful reminder of that. We can promote this rich if hidden biosphere by building a compost pile and forgoing chemical sprays that can harm soil life. “If gardeners stay away from pesticides and add lots of organic matter to their soil, the fungi will come,” Nardi says. “Fungal spores are ubiquitous.”

As someone who gets vegetables, fruit and honey from the garden, I’d love to get to know mushrooms better for the plate. To do this correctly, however, I’d have to join a club of knowledgeable foragers. Until that happens, I’m content simply to observe the mushroom display that follows a period of soaking rain and think about the world beneath our feet.

Follow @adrian_higgins on Twitter for updates on gardening and other cosmic events.

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