Types of Mushrooms

Beware of Mercury When Picking Wild Mushrooms

Wild mushroom foraging continues to be a popular past time for fun and food, however the continued accumulation of scientific research suggests it could turn into a hazardous past time.

Consider the findings of the following two articles examining the toxic content of various edible mushrooms, especially with respect to Mercury.

  • Metal Exposure in Boletus edulis
    Here we present the first evidence of peptides of the phytochelatin family being responsible for binding a large fraction of Cd in caps of the macromycete Boletus edulis exposed to excess metals. Concentrations of Cd, Zn, Cu and Hg, as well as cytosolic Cd-binding capacity (CCBC), glutathione (GSH) and free proline (Pro) were quantified in fruiting bodies of B. edulis differentially exposed to a wide range of metals.
  • Contents of Cadmium and Mercury in Edible Mushrooms
    Some species, mainly from the genera Agaricus, Macrolepiota, Lepista and Calocybe accumulate a high content of cadmium and mercury even in unpolluted areas. Levels of these metals increase considerably in heavily polluted sites, such as in the vicinity of both working and abandoned metal smelters or inside cities.

The articles suggest a general consensus forming around the fact that wild mushrooms growing near metal smelters and within the wind range of fossil fuel power plants, especially coal fired power plants, contain harmful levels of mercury.

According to the Center for Disease Control (CDC), children are especially susceptible to mercury exposure. They state,

Mercury's harmful effects that may be passed from the mother to the fetus include brain damage, mental retardation, incoordination, blindness, seizures, and inability to speak. Children poisoned by mercury may develop problems of their nervous and digestive systems, and kidney damage.

The third article concluded, "The total mercury concentrations were compared to data in the literature and to levels set by legislation. It was concluded that consumption of the majority of the studied mushrooms is not a toxicological risk as far as mercury content is concerned, although the species B.pinophilus, A.macrosporus, L.nuda and B.aereus should be consumed in low amounts."

Because many boletus species are considered choice edibles, the word to the wise can be supplemented with a map for the wise.

The Mercury Emissions Map of the United States shows the areas either currently subject to high mercury emissions levels or susceptible to mercury emissions because of their proximity to coal fired power plants.

The entire Appalachian trail, along with the Upper Great Lakes areas, popular wild mushroom hunting areas, are situated in the mercury warning areas.

With the exception of a small area on the border of Washington and Oregon, along with a large area in the mining area of Northern Nevada, much of the area in the Cascades and Sierra Mountains of the West shows little mercury susceptibility.

Types of Mushrooms

Using tabs furthers the mushroom conversation. The gallery provides information on different types of mushrooms from a handful of mushroom families.

picture of inky cap mushrooms

Inky cap mushrooms often grown in residential areas. As the fungi ages, the gills begin turing an inky black.

picture of a manzanita bolete mushroom

Most people associate pores with bolete mushrooms. The mushroom in the picture also displays visible scabers on the stipe, indicating a leccinum species, l. manzanitae, or Manaznita bolete

picture of an admirable bolete

The Admirable Bolete (Boletus mirabilis), a striking mushroom, grows on tree stumps.

picture of a pair of Fly Agaric mushroom

Amanita often get introduced as some of the most poisonous wild mushrooms in North America. The over one hundred documented North American species share physical characteristics such as the presence of a veil that covers the mushroom during the maturation process, with veil remnants visible on the fungi's mature caps.

Fly Agaric, the common name for Amanita muscaria, is recognized by the orange spotted top, as shown in the top picture, represents the last stage of fruiting.

picture of a Snow Mushroom

The snow mushroom (Gyromitra montana) receives its name based on its habit of fruiting at higher elevations in the West along the snow melt line.

Research over the past couple of decades has led to some confusion among Gyromitra species, with debate existing as to whether Gyromitra gigas and Gyromitra montana should be considered the same species.

Physically, the mushroom grows very close to the ground, often with only the rounded cap showing. Its low growing feature helps differentiate it from other Gyromitra species that grow on longer, above ground stipes.

Gyromitra montana sometimes gets called the false snow morel and brain mushroom.

picture of a gilled bolete

Most boletes fit the category of pored mushrooms. The Gilled Bolete (Phylloporus rhodoxanum) goes against the grain. A handful of Phylloporusgenus species grow in the United States, some bruise blue, others do not. The picture additionally highlights the bright yellow gills.

picture of a purple cort mushroom

Cortinarius, the world's largest genus of mushrooms, gets its name from the partial veil that covers the cap of the young fruiting bodies. The presence of lamellulae, or short gills also provides a good field ID clue for Cortinarius species.

Caps and stipe come in a variety of red, brown, tan, yellow and purple shades. The picture shows the very purple Cortinarius violaceus.

picture of a club mushroom

Coral Mushrooms, a colorful group of mushrooms, fit into a handful of mushroom orders. The picture shows a club coral in the clavaria genus.

Typically Clavariaceae species tend not to be the dominant mushroom family found in any area. However, many of the brighter colored species can be easy to spot as they stand out against their typical green and brown forest background. When the colorful species are not readily visible, try looking around the base of downed trees or stumps. Smaller corals often sprout in the area.

picture of a morel mushroom

Morel mushrooms (Morchella) ranks at the top of the edible mushroom list. Mushroom hunters know them as spring fruiting fungus, often associated with either recent burn areas or deciduous forests, although they can be found in coniferous forests.

While morel mushrooms grow in a variety of habitats across North America, finding them can be difficult. It's probably more accurate to say that morels pick humans rather than the other way around. Without practical knowledge about specific morel growing spots, often gained by year after year success with a specific location, mushroom pickers can literally walk themselves in circles around potential growing spots without finding any. Sometimes not looking for them helps. That's the time they begin to pop up on the side of the road somewhere.

They can grow large, over six inches with stem. Generally two types can be found, easily differentiated by the shape of the honeycomb patterned cap.

The picture shows a yellow morel with a round cap. Yellow and black morels contain a toxic substance so they cannot be consumed raw. Cooking them easily removes the toxin.

Like boletes, morels retain their flavor when dried. Unlike boletes, they are hollow on the inside.

Drying Mushrooms

Dried mushrooms are the second best thing to fresh mushrooms.

Whether found in fields and forests, or purchased at a local market, most mushrooms have a limited shelf life. Drying them extends the shelf life.

Of course, not all mushrooms are created equal for drying. Mycologists and culinary enthusiasts generally recommend morels and some bolete species as the prime candidates for preservation by drying. They are among the few mushroom genera that retain their flavor and texture when dried and reconstituted.

As most mushroom foragers known, picking wild mushrooms for drying requires caution. Many bolete species, but not all of them, are considered choice edibles. Others can cause gastronomical distress. Likewise, poisonous morels, or false morels, compete with choice morels for the average mushroom picker's attention.

The top picture in the box shows a bolete mushroom cut in half with the pores removed. The flesh is white except for a bruise on the lower part of the stem.

The worm holes and decaying flesh of the mushroom in the second picture indicate that the mushroom is well past its prime. A close look at the picture also shows some blue discoloration on the mushroom stem. Mycologists generally warn against eating any blue staining bolete species.

A field check for bluing is easy and is accomplished by ruing a thin object across the pores. Breaking off a piece of the cap also promotes bluing.

The picture also brings to mind the old truism, buyer beware. Purchasing wild mushrooms from local vendors carries risks. Requesting vendors cut fresh mushrooms in half prior to purchase is a generally accepted practice at farmer's markets.

With mushrooms in hand, the actual drying process begins with preparing the mushroom. Preparation initially involves cleaning the mushrooms.

Using a clean cloth to remove excess dirt, and where applicable pores, from the mushroom usually completes the cleaning process. Mushrooms tend to absorb water, so experts recommend against soaking them in water for cleaning purposes.

Preparation continues with slicing the mushroom, with the size of the slices individually determined. In drying situations, typically uniform slices dry more uniformly.

After slicking, mushrooms can be set on the trays of a conventional dehydrator set at a low temperature, no higher than 120o, for approximately six hours. Higher drying temperatures tend to cook rather than merely dry mushrooms.

When the mushroom pieces completely dry, they look leathery. Placed in an air tight container, expect the dried mushrooms to have two year shelf life two year shelf life.

© 2007-2012 Patricia A. Michaels. All Rights Reserved.