Mushroom of the Month, May 2018: Hemlock Varnish Shelf, Ganoderma tsugae

A Field Guide to Mushrooms of the CarolinasToday we initiate a new monthly series, Mushroom of the Month, brought to you by Michael W. Hopping, co-author of A Field Guide to Mushrooms of the Carolinas:  A Southern Gateways Guide, just published by UNC Press. 

Mushrooms in the wild present an enticing challenge: some are delicious, others are deadly, and still others take on almost unbelievable forms. A Field Guide to Mushrooms of the Carolinas introduces 650 mushrooms found in the Carolinas–more than 50 of them appearing in a field guide for the first time–using clear language and color photographs to reveal their unique features.

A Field Guide to Mushrooms of the Carolinas is available now in both print and ebook editions.

Look for more Mushroom of the Month features on the UNC Press Blog in the months ahead.

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Hemlock Varnish Shelf, Ganoderma tsugae

Hemlock Varnish Shelf, Ganoderma tsugae

Hemlock Varnish Shelf, Ganoderma tsugae (Photo by Michael W. Hopping)

The polypores or bracket fungi are a diverse assemblage of wood rotters whose members typically dress in bureaucratic browns, grays, or dirty whites. Timid nonconformists might opt for a striped cap, decorative scales, a hairy upper surface, or mossy accents. But even here, among the ranks of work-a-day polypores, can be found a few in open rebellion against drab expectations. In the Southern Appalachians the little red corvette of these miscreants is the Hemlock Varnish Shelf, Ganoderma tsugae, also known as Hemlock Reishi.

As a group, young varnish shelf mushrooms set themselves apart with a dry but shiny (varnished) upper surface. Four species are currently recognized in the Carolinas. Two inhabit deciduous trees, one prefers pine. Not surprisingly, the Hemlock Varnish Shelf specializes in Eastern Hemlock but can also occur in firs and possibly other conifers.

Each spring a new crop of brackets, first appearing as soft white balls, sprout on the trunk or at the base of an infected tree, log, or stump. The developing mushrooms morph into fan-shaped caps up to 31 cm wide. These are anchored by short, stout stalks to the fungus hidden in the wood or tree roots. The shiny upper surface of growing caps is brightly colored, often in flaming shades of red or orange and peripherally zoned with a band of yellow then white at the cap margin. The underside is also whitish, consisting of a densely packed field of tiny (4-6/mm) pore openings. Damage to the pore surface causes a brown discoloration. Although white parts of the Hemlock Varnish Shelf are edible when young, the flesh soon becomes tough and unpleasantly bitter.

By mid-summer the caps have matured and begun to fade. The top darkens to a uniform reddish brown or burgundy. Any residual varnish shine may disappear under a brown dusting of spores. The once white pore surface and interior flesh turn brown as well.

Ganoderma tsugae is prized in the alternative medical community by virtue of its very close relationship to Lingzhi, a Ganoderma species with a 2000 year history of medicinal use in China. In Japan it is called Reishi. Science long knew it as G. lucidum, a rotter of deciduous trees. But genetic analyses of specimens obtained from around the world have complicated matters. The classical concept of “G. lucidum” proved to contain several species, and these possess widely differing amounts of the compounds thought to benefit health. Ongoing studies are needed to confirm therapeutic activity and which species are good for what. A conservative overview of the clinical state of affairs is accessible at https://www.mskcc.org/cancer-care/integrative-medicine/herbs/reishi-mushroom

Ganoderma lucidum proper turns out to be European, but the Carolinas are home to a pair of species sometimes labeled as such. Ganoderma curtisii has a stalk; G. sessile does not. Both infest/recycle deciduous trees. Widespread commercial production of “G. lucidum” in the broad sense, ensures that those mushrooms and mushroom products can be found as well. For G. tsugae though, the supply chain still begins where it always has, in the woods, on dying or dead Eastern Hemlock trees.

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Michael W. Hopping, a retired physician and author, is a principal mushroom identifier for the Asheville Mushroom Club. You can read his previous blog posts here and here.