Sulphur Shelf
Common Name
: Sulphur Shelf, Chicken-of-the-Woods, Chicken mushroom, Rooster Comb, Polypore soufré (French), Schwefelporling (German), Трутовик (Russian – pronounced ‘troo tow vick’) – The fungus grows in overlapping shelf-like, semicircular brackets with a spore-bearing pore surface on the underside of the bright orange caps that is sulphur yellow in color – it is a Sulphur-colored Shelf-type fungus.

Scientific Name: Laetiporus sulphureus - The Latin word laetus means ‘fat’ or ‘rich’ when applied to animals and ‘fertile’ when applied to either land or plants. The generic use here probably refers to the refulgent appearance of the pores (Latin porus). Sulphureus is Latin for sulfurous; the yellow-hued element sulfur (atomic number 16) was a well-known in the ancient world as both a medicine and as a means of fumigation. An alternate scientific name that is often used is Polyporus sulphureus.

Sulphur or Sulfur (both are correct orthographies) Shelf is among the most recognizable of all the edible fungi and is accordingly gathered with justifiable reckless abandon by neophyte mycophagists; it has no look-alike doppelgangers (at least in the Mid-Atlantic States region). The exploded rosettes of violent orange are hard to miss and can be discerned in even the densest of woods even from across a ravine. The profusion of individual and overlapping fan-like fruiting body caps from a single source readily fills a large rucksack from which many meals can later be created; a veritable forest fungal cornucopia. Charles McIlvaine in One Thousand American Fungi provides the anecdote that: “On an old willow at Mt. Gretna, a cluster 18 inches across afforded a dozen meals. Whenever a meal was wanted a pound or two was broken off. It lasted until January.” They can and do get quite large; the 2009 Guinness Book of World Records lists a Chicken-of-the-Woods mushroom found in New Forest, Hampshire in the United Kingdom on October 15, 1990. It weighed 100 pounds (45.35 kg).

Cooking Sulphur Shelf
The common name Chicken-of-the-Woods captures the gustatory sensation elicited by the fungus; when cut into small chunks and sautéed, it has the look, texture and taste of the white breast meat of a chicken. It doesn’t look anything like a chicken, unlike the Hen-of-the-Woods (Grifola frondosa) which actually does look like a hen sitting in the woods. The Chicken-of-the-Woods should also not be etymologically confused with the Fried-chicken mushroom (Lyophyllum decastes) which tastes like fried chicken – the two “chicken mushrooms” bare no physical similarity. McIlvaine, the audacious and self-proclaimed American authority on fungal edibility (mycophagism) - his stated quest was to research mushroom varieties (he relishes in calling all fungi ‘toadstools’) that would “appease the appetite of a hungry naturalist” - offers the following advice: “If P. sulphureus is cooked properly it is a delicious fungus. Cut fine, stew slowly and well, season, add butter, milk with a little thickening.” The photograph affords a cook’s eye view of the commendable result.

There are a few caveats to the universal appeal of the Sulphur Shelf as an edible fungus. It is an unlikely looking food source, as bright colors quite frequently indicate toxicity, the aposematic coloration of animals such as the poisonous red eft a case in point. With characteristic aplomb, David Aurora offers his version in the classic Mushrooms Demystified: “There is always an element of disbelief in stumbling onto a large cluster – it looks like something out of a Jacques Cousteau movie. You would no more expect to find it on an aging eucalyptus stump by the railroad tracks than you would expect to find a freight train at the bottom of the sea.” He also addresses the other caveat to eating this fungus; there have been reports of Sulphur Shelf poisoning, particularly in California and the Pacific Northwest. Most field guides offer cautionary notes relating to observed side effects. Gary Lincoff, the generally acclaimed doyen of amateur mycologists and author of The Audobon Field Guide to North American Mushrooms, writes that “It becomes somewhat indigestible as it ages and, in some, causes an allergic reaction, such as swollen lips.” He also notes that the apparent toxicity is related to the host on which the fungus is growing, with a specific caution against those found on eucalyptus trees, which are native to Australia and which were introduced into California and thereafter spread northward through the Pacific Northwest. Is there a need to be cautious when eating Chicken-of-the-Woods? Depending on where you gather them, yes.

Laetiporus sulphureus var. semialbinus or Laetiporus cincinnatus
Until recently, the Sulphur Shelf had been thought to be a single species with perhaps one variation; it has long been observed that a variant of L. sulphureus could be occasionally found that had white pores instead of the standard sulphur-colored pores. This variant was known as either Laetiporus sulphureus var. semialbinus (Latin for ‘half white’) or as Laetiporus cincinnatus (from the Ohio town of Cincinnati where it was first identified). Recent research has revealed that there is much more complexity to the genus than macroscopic observation alone would provide. A seminal paper entitled “The Genus Laetiporus in North America” by H. Burdsall and M. Banik was published in the Harvard Papers in Botany (Vol. 6 No.1 pp. 43-55) in 2001. This paper reported on a number of separate studies on the taxonomy of L. Sulphureus. Based on an analysis of 116 separate Sulphur Shelf collections, which involved not only the genotypic methods of polymerase chain reaction and restricted fragment length polymorphism but also the traditional pairings to determine sexual compatibility, the unexpected conclusion was reached that there may be five or six separated species in North America.

L. conifericola
The species of Laetiporus can be distinguished based on geographical, environmental, and growth factors. In addition to the original L. sulphureus and L. cincinnatus, the taxon now includes L. conifericola, L. gilbertsonii, L. huroniensis and L. percinus. One of the major findings of the Harvard study is that the fungi on the west coast are different from the fungi elsewhere. These are L. conifericola, which, as its name implies, grows only on conifer trees and L. gilbertsonii, which grows only on oak (Quercus) and eucalyptus trees; it is named for Robert Gilbertson, a noted mycological taxonomist. As can be seen in the photograph taken of a Sulphur Shelf type fungus growing on a fallen conifer tree in Olympic National Park, L. conifericola is essentially indistinguishable from its Eastern cousins. Reports of the apparent toxicity of Sulphur Shelf that emanate from Western North American sources are indubitably due to the fact that they are talking about a different species. For example, Michael Beug, a mycology professor at Evergreen State College in Olympia, Washington, reports that ingestion of either of the western variants can cause gastro-intestinal distress in the form of nausea and vomiting. Further, he states that “One young British Columbian girl who ate Laetiporus conifericola raw became disoriented, lost coordination, and described visual hallucinations.” The constituent components of any species are a direct result of what it ingests from its environment. It is therefore quite probable that the unique enzymatic content of the Laetiporus species that grow on conifers and eucalyptus trees is at the heart of the mysterious reports of Sulphur Shelf sickness.

The Harvard study also addressed some significant differences between L. sulphureus and L. cincinnatus other than the readily discerned difference in the lighter color of the spore-bearing pores on the underside of the cap of the latter. This is of some importance as the two species overlap in geographical habitats in Eastern North America. The differences are associated with the manner in which the nutrients are extracted from the host tree. L. cincinnatus extracts nutrients from the tree’s roots or from the butt of the tree which is that part adjacent to the roots. It is therefore the only Laetiporus species that can be found fruiting on the soil (the hyphae extending to the roots below), though it is normally found further up the tree to a height not exceeding five feet. L. sulphureus, on the other hand, is a heart rot fungus, meaning that it extracts its nutrients from the heartwood of the tree. When a tree grows and the trunk diameter increases, the innermost part or “heart” at the center of the bole relinquishes its role of water and nutrient transport to the outermost layer, which is called the sapwood. The heartwood provides the core support at the center of the tree. When the heartwood is parasitized by the L. sulphureus, the tree is weakened by the reduction in its load carrying capacity. This can have dire consequences for the (mostly) oak trees that are its predominant host. According to Fungal Strategies of Wood Decay in Trees by F. Schwarze, a study conducted in 1990 in England after the “Great Storm of 16 October, 1987” found that “L. sulphureus was the secondcommonest fungus species associated with failure of tree stability and fracture-safety of all trees investigated.” The cause was reputed to be the destruction of the heartwood of the trees and the concomitant loss of strength against wind shear forces.

The mild toxic qualities of some species of Sulphur Shelf are due to the production of proteinaceous substances synthesized by the fungus over the course of evolutionary history. One such enzyme is tyrosinase which is used to assist in the oxidation of the phenols in the heartwood of the host tree. The likely source of Laetiporus toxicity is a lectin called LSL, which induces both hemolytic (release of hemoglobin) and hemagglutinating (coalescence) of red blood cells. Foods with high concentrations of lectins (which include some beans, seeds and nuts) can cause gastrointestinal distress, particularly if consumed uncooked and in excess. This is the fundamental reason why it is advised to cook all fungi and to eat them in moderation. It should come as no surprise that Sulphur Shelf enzymes, if used in appropriate quantities against an appropriate malignancy, would likely have medicinal properties as well; lectins are known to lyse some cells. There is some evidence that Laetiporus fungi inhibit the growth of some bacteria, notably Staphylococcus aureus of staph-infection infamy.