The fungus among us

The frilly underside of mushrooms, full of spores. — Linda Fortuna/Creative Commons

The damp, mild weather of spring and fall is perfectly suited to the overnight appearance of some of the strangest life forms we know - the mushrooms.

Not an independent plant at all, the mushrooms we see above ground are really only the fruiting bodies of a larger fungus whole. They are attached to a net of threadlike fibers (known technically as the mycelium) "like apples on an apple tree," as one writer puts it. Actually, it might be more useful to think of them as the vegetative tip of an underground iceberg.

One of my all-time favorite news stories concerned the discovery in 1992 of a mushroom fungus living underground on the upper peninsula of Michigan that was estimated to weigh 220,000 pounds (about the same as a blue whale). Covering 37 acres of forest floor and believed to be at least 1,500 years old, the specimen of Armillaria bulbosa rates as one of the largest and oldest living creatures known to modern science.

Its fruiting bodies, known as honey mushrooms for their color, were innocuous enough. But below the surface, drama: Its dense, shoe-string sized tentacles invade and digest dead tree roots. Snaking slowly through the soil, they locate their helpless prey and secrete an enzyme that dissolves wood into a form it can consume.

Once they've located a rich vein of rotting root, the fungus strands tunnel into it, burrowing through the roots as far into the underground depths as they descend. Sounds like a slow-motion horror movie. Pretty creepy, no?

I was thinking about the surprising nature of mushrooms lately when my newly tilled flower bed suddenly sprouted a crop of weird 'shrooms that looked like death stars. Perched on a ghostly white stalk, maybe 6 inches tall, was a spooky black "flower" with gills pitched upward in malevolent imitation of the clove-scented pinks.

It may have been the humus, the dried manure or the Michigan peat (Michigan - oh, no!) I had tilled into the soil that carried, unbeknownst to me, the spores of this fungal intruder. It could have been the covering blanket of mulch, hugging the sun's warmth to the earth, that brought them out in such numbers. I don't mind telling you that I found them a little off-putting..

''Let it rot" could be the motto of the fungus among us. God knows, they love whatever decomposes, a process they are happy to help along. Many of the mushrooms that spring up suddenly in your lawn or shrub borders are actually feeding on the decaying wood of an underground stump or dead tree roots. Not to ruin your appetite, but many commercially grown mushrooms are nourished on the partially decomposed cellulose produced by the inefficient digestive system of the horse.

Honey mushrooms, big - really big - in Michigan. — ressaure/CC

Like you, probably, I've seen many different kinds of mushrooms in the yard over the years, especially in periods of sustained wetness. The conventional toadstool kind is usually a mottled brown on top, but the cap also can be white, yellow, red or a combination thereof.

I've seen bright red ones, tubular in form, that look like ICBMs emerging from underground silos. I've had shelf fungus attached to trees that were half the size of dinner plates and one ground-dwelling mushroom that, when broken apart, turned from milky white to bright blue right in front of my eyes.

As mycologists (mushroom specialists) can tell you, the common names of various mushrooms are wonderfully weird: shaggy mane, bearded tooth, hen-of-the-woods, death cap, sulfur shelf, coral fungi, doghair mushroom and jack-o-lantern, an orange kind that sometimes glows in the dark.

Unless you are trained by someone definitely in the know, it's better to refrain from eating your finds. Most poisonous mushrooms disturb the digestive system with diarrhea and vomiting, or cause swollen lips, headaches or hallucinations, but it can get worse; a single cap of the mushroom known as the destroying angel (Amanita virosa) can kill a good-sized man.

These mushrooms contain one of the deadliest poisons known and the sneaky little devils look like innocent puffballs early in their development. No matter what you have heard, there is no magic trick that will help distinguish edible from poisonous mushrooms - forget testing with silver spoons, boiling with copper pennies, peeling the caps and all the rest of that folklore.

One fun thing you can do with your mystery mushrooms is to make a spore print. Individual spore are too tiny to be seen with the naked eye, but spore prints will show their distribution and color, an important tool to identification.

Here's what you do: Carefully cut off the stem and place the mushroom cap gill-side down on a piece of white paper. Cover with a bowl or jar and leave undisturbed. If the mushroom is at the spore- shedding stage, a print will gradually develop like a photographic image emerging in a chemical bath.

You can see remarkable detail, including the arrangement of parallel gills, meticulously outlined in the ghostly spore dust. It's fun, it's harmless and obviously collecting mushrooms for this activity won't much impact the more massive fungus body below ground.

Just don't lick your fingers.