Fairy Rings

A perfect circle of mushrooms.  They pop up after a rain in summer or fall.  A fairy ring.  The name suggests magic and there is a deal of biological magic taking place.  There are several fairy rings in our suburban neighborhood in North Carolina.  The one we see the most is a ring of the poisonous mushroom Chlorophyllum molybdites. This fairy ring starts with a single, microscopic spore of the fungus landing in the soil.  This spore germinates and sends out hyphae, microscopic threads of cells, that absorb nutrients from the soil.  The hyphae grow out symmetrically in all directions making a circular colony fungus. As the colony gets larger the older part in the center dies and the living portion is along the perimeter of the colony.  When the moisture and temperature conditions are right, the hyphae on the circumference send up mushrooms in a ring.  The mushrooms carry out sexual reproduction and release more spores.  These spores float through the air and if they land on a favorable patch of ground, a new fungal colony can form.    

A fairy ring of Chlorophyllum molybdites on a lawn in Salisbury, NC. 

Chlorophyllum molybdites makes a large white mushroom.  The stalk of the mushroom has a distinctive ring just below the cap.  The mushroom’s cap has off-white scales on the top and spore producing gills on the bottom.  One of the unique features of Chlorophyllum molybdites is it makes green spores.  The spores give the gills a pale green color too.  Spore prints are a good way to see the color of fungal spores.  To make a spore print you remove the stalk from the mushroom, lay it on a piece of paper, cover it with a bowl and wait 24 hours.  The spores are released and fall straight down onto the paper making an exact print of the gills and showing the color of the spores too. 

A single mushroom of Chlorophyllum molybdites just emerged from a lawn.

Two Chlorophyllum molybdites mushrooms with scales on the cap. 

The underside of the cap of Chlorophyllum molybdites showing the ring on the stalk,

A closeup of the gills of Chlorophyllum molybdites with the green color.

Spore print of Chlorophyllum molybdites.  The spores make an exact impression
of the gills and show the spore color.

Chlorophyllum molybdites has several common names.  The most interesting is vomiter from the consequence of ingesting this poisonous mushroom.  Chlorophyllum molybdites causes most of the mushroom poisoning cases in the United States.  A person unlucky enough to eat Chlorophyllum molybdites experiences gastrointestinal distress.  It starts with cramps, then vomiting and diarrhea, sometimes-bloody diarrhea.   Chlorophyllum poisoning is almost never fatal and the symptoms clear up in a couple of uncomfortable days. 

Fairy ring season is upon us.  Enjoy the magic but don’t eat the mushrooms.