Sulphur Shelf Mushroom
October 15, 2019
What kind of organism is a fungus? Certainly not a plant, although
until recently even scientists believed that was the case.
However, most fungi build their cell walls out of chitin, the same
material as the hard outer shells of insects, and plants do not make
chitin. Now it has been determined that they are more
closely related to animals, and have been placed in their own
Kingdom. The body of the fungus is made up of a web of
microscopic filaments that are buried in the soil, in wood, or in
another food source. These webs live on and grow unseen
until they develop mushrooms, puffballs, truffles, brackets, cups,
“birds nests,” “corals” or other fruiting bodies.
The fruiting bodies often seem to sprout up overnight. They can do this
because when they begin to enlarge they already contain their full
complement of structural cells. It requires only a heavy rain to fall,
at which time the fungus body pumps water into these cells, and almost
overnight some mushrooms can go from pin-head size to full size.
Generally, we avoid picking the numerous mushrooms we find along our
hiking trails as we don’t have the expertise to be confident in
identifying the edible varieties. Two exceptions are the morel and the
sulfur shelf. Most Wisconsinites are familiar with the
morel, but unless you frequent the woods you may not have seen a sulfur
shelf. This large fungus, which is also known as
“chicken-of-the-woods”, announces its presence with a bright orange top
and gorgeous sulfur yellow underside. Called a bracket or shelf
mushroom because of the way it extends from a tree trunk, the sulfur
shelf is often found on or around an oak tree and often comes back year
after year. One year, we discovered a huge specimen growing
in the farmyard on our old willow.
Young sulfurs are moist, rubbery, and easily broken, while more mature
specimens become pale, tough, and are often dotted with insect holes.
Many think that the texture and even flavor is reminiscent of chicken,
but those who would like to try it should be aware that, as with any
mushroom, some individuals have a bad reaction, including
light-headedness and nausea. "The neat thing is that it is impossible
to misidentify," said Greg Mueller, curator of mycology at Chicago’s
Field Museum. "It's the only big, bright orange bracket mushroom with
sulfur pores growing on wood out there." This was pretty much the
accepted wisdom well into the 1980′s, but as allergic reactions seemed
to become more numerous, it was found that specimens growing on certain
trees and in certain areas sometimes did cause problems and gastric
distress. Eucalyptus, evergreens, and locust in particular were suspect
and the advice now given is to avoid any sulfurs collected from these
The sulfur shelf grows in large flattened fans that lie in horizontal
tiers, sometimes becoming huge and weighing as much as a hundred
pounds. It is more accurately called a polypore because, rather than
having gills underneath its cap like many other mushrooms, it has
tubes, or pores -- tiny holes dotting the underside. These are lined
with spore-producing organs, as fungi must produce enormous numbers of
spores so that at least a few will land on favorable surfaces for
All polypores have two or three kinds of cells -- the rapidly expanding
inflatable generative cells, along with two kinds of reinforcing cells,
referred to as ‘binding’ or ‘skeletal’. The hard woody conks you see on
trees have all three and will persist on their hosts for several years.
The sulfur shelf has but two -- the quickly expanding (and edible)
generative type, and the more rigid, slower growing binding kind. These
latter cells give the fruiting body strength and rigidity and can even
hold it together for a time after the softer tissue dries out and
The sulfur fungus may grow inside a tree for some 50 years in order to
build up enough energy to form the colorful fruiting bodies, and during
that time it is feeding upon the tree's inner tissues, causing decay.
All wood is composed mostly of two substances -- cellulose which is
white and forms the primary wall of all plant cells, and lignin which
makes up the brown inner wall in some cells, especially those of trees.
Polypores, such as the sulfur shelf, harbor both brown rot fungi that
degrade only the white cellulose leaving the brown lignin to crumble to
dust, and white rot fungi that decompose the lignin and leave the white
stringy cellulose behind. As the decay proceeds, hollows are created
that house all sorts of creatures, and eventually the fungi will
accomplish the transformation of the tree into soil.
Meanwhile, springtails, nematodes, and other tiny beings graze on the
fungi inside the tree, while fungus gnats, fungus flies, pill bugs, and
various fungus beetles feed on the shelf fungus itself and are in turn
picked off by birds. These fungi play an important role in the health
and vigor of the forest but harvesting their fruits will cause no harm,
and we can enjoy discovering the eye-catching color amidst all the
green, and have it for supper, as well.