Notes from the Field Station: Fall is a Good Time for Mushrooms

Tuesday, October 11, 2011

With the seasonal return of rain and a drop in temperatures, mushrooms will happen.  Those creatures, sometimes called fungi or molds, deserve our attention at the Field Station for many reasons.  They intrigue us and they are beautiful.

They are nature's recyclers and are, simultaneously, handsome in their own way.  At a time not too long ago (as when I was a college student) fungi were considered part of the Plant Kingdom.  Now with revised taxonomy and the tools of genetics and chemistry they are placed into their own Kingdom Fungi.  They deserve that.  The more we learn about them, their chemistry and life cycles, the greater become their differences with plants. Fungi grow without sunlight and display unusual reproductive habits. 

At latest count, more than 70,000 species of fungi have been described in the technical literature.  That may be only a fraction of the total number of kinds of these creatures.  We could be talking millions.  In recent years, about 1,000 new kinds of mushrooms are discovered every year.

Several hundred beauties, all the same kind of mushroom, are growing under white pines in a plot of the Field Station that parallels the Fayette-New Wilmington Road.  Technically, they are Amanita muscaria.  Otherwise they can be called toadstools or poisonous mushrooms.  They grow to a height of six inches and have an umbrella about five inches in diameter.  The umbrella is yellow-orange and has what appear to be scales on the top.  The white stalk has a ring, called an annulus or veil, just below the umbrella.  They are loosely attached to the ground below the pines.  Their attachment, though fragile, is very complicated.  Tiny threads, called hyphae, are their "roots" and extend out from the mushroom 20 to 100 feet. In actuality, all of these mushrooms amid the pines may be connected by their hyphae to each other and to the actual roots of the pine trees.  Hyphae that penetrate root tissues are called mycorrhizae. These amanita mushrooms are beautiful but poisonous to humans.  Strangely, some rodents feed on them with impunity and never suffer or die.

Not too far from the patch of amanitas is another spot near our Nursery where mushrooms of a different sort thrive.  These look more like lost soccer balls than mushrooms.  They are called giant puffballs or Calvatia gigantea.  That's a good name.  They have no umbrella or stalk but, like the amanitas, have an extensive underground network of hyphae.  For humans, the big difference is that the giant puffball is flavored for our taste and is an edible delicacy.  Cut this puffball open and the inside looks like angel food cake.  Sliced and sautéed with sizzling butter, it graces any table food (for those who like mushrooms).

Across the Field Station in our Arboretum and growing on an old cherry tree stump is a mushroom that definitely fits the season.  This is the Jack O' lantern mushroom, or Ompholotus, that definitely deserves mention in this time before Halloween.  Here are two special features: It is a brilliant orange in color and shows a spectacular phenomenon called bioluminescence.  It actually glows in the dark.   What more could one want from a Jack O' lantern?  Be careful, this one is mildly poisonous.

What these three mushrooms have in common, besides their ability to obtain their organic food in the soil by way of hyphae, is their reproductive cycle.  All are what we call Basidiomycetes, producing spores on little clubs (called basidia).  Genetically, the spores are of two types, indistinguishable under even the best of microscopes.  We don't call them male or female, just "plus" or "minus" spores.  The spores will grow their own hyphae and eventually "plus" hyphae meet "minus" hyphae underground.  Voila!  They are attracted to each other.  They begin fertilization.  They then grow their own "combination plus/minus" hyphae that become the familiar above-ground mushrooms.  The cycle is complete - no egg, no sperm, just two kinds of hyphae with genetically different nuclei that fuse and flourish.  This happens with amanitas, giant puffballs, Jack O' lanterns as well as the common agricultural mushrooms we buy in the grocery stores or eat as a delicacy on pizza.

So, what makes one mushroom poisonous and the other not?  Or, as I'm often asked, how do you tell a poisonous one from a good one?  Here is the short answer.  It takes two to tell - one to eat the mushroom and the other to take notes.  Chemistry provides the technical answer.  Each kind of mushroom produces unique chemicals under genetic control.  Some of these chemicals are toxins or poisons; they interfere with our metabolism and we suffer pain or even death.  Amanitas produce "amatoxin" that prohibit processes essential to protein synthesis.  When amatoxins are ingested, cell metabolism grinds to a halt and each cell (and eventually the human body) dies or becomes very ill. 

The best advice is to select mushrooms in the store or, if going for wild ones, do that with an old timer who had "been there done that" before you!  An axiom of worth is:  There are old mushroom hunters and there are bold mushroom hunters; but there are no old, bold mushroom hunters!

Clarence Harms, Director
Field Station
(724) 946-6001

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Jack O'lantern mushrooms growing on a cherry tree stump


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Poisonous Amanita mushrooms grow amid roots of pine trees


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Giant puffball with insides that are white and edible when young