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Hemlock Varnish Shelf - Ganoderma tsugae


Ganoderma tsugae

Good evening, friends, and Happy Independence Day!

This week’s mushroom is the Hemlock Varnish Shelf (Ganoderma tsugae). This mushroom is the third of five northeastern Ganoderma species I’ve written about, but the only one you probably won’t find in NYC. That’s because it grows almost exclusively on eastern hemlock trees (Tsugae canadensis) of which, unfortunately, there aren’t many within in the five boroughs.


In 1937, hemlock made up 37% of the canopy in the New York Botanical Garden's Thaim Family Forest, but in 2011 it was down to 4% - and likely less than half of that currently. The loss of hemlock at NYBG is representative of the tree’s decline across the northeast and is primarily caused by two invasive insects. The hemlock wooly adelgid (Adelges tsugae) and elongate hemlock scale (Fiorinia externa) suck nutrients from the needles and branches eventually leading to the trees’ demise.


At full strength, hemlocks can grow 70’ tall and stretch 35’ wide at the base - large enough to create their own microclimates that are moister and shadier than the surrounding forest. Today we’ll learn how even in death, hemlocks give life to fascinating microhabitats and ecosystems - none more impressive in stature than Ganoderma tsugae.


Ganoderma tsugae
G. tsugae with dusty brown spores covering the near part of the red-shellacked cap.

Fun Facts

This mushroom has a "laccate” cap which describes the glossy red, or lacquered, color and texture of the cap. There is some thinking that it is a biennial (the mushroom grows every other year) even though the fungus exists in the wood year-round. In my experience at Manitou and in other areas in the northeast I’ve found that to be the case. The trees on which G. tsugae were growing last year don’t have fresh mushrooms this year, and the specimens I’ve included today were not seen in these spots last year.


Ganoderma tsugae

The mushroom isn’t considered edible, it’s very dense and woody, but it is revered for potent medicinal properties. In North America this is a native species of Reishi - a medicinal mushroom you might have heard of or even used as a powder/extract. Extracts and teas of the mushroom are used for everything from blood sugar regulation to histamine control to anti-cancer/anti-tumor prevention.


In east Asia they call Reishi “the mushroom of immortality” because it has been used there for centuries, many times for anti-aging purposes (the native Ganoderma species in east Asia are G. lingzhi and G. lucidum). Anecdotally, a friend told me it helps stimulate their creativity and drinking reishi tea for several weeks helped give them the motivation to start their own business.


Ganoderma tsugae
Brown bruising will occur on the white pour surface of the mushroom.

There are tons of studies in vitro (in a lab setting) and in vivo (in a living organism) to substantiate these medicinal claims, but one specific study from 2022 (Reference 2), showed that compounds found specifically in G. tsugae had a beneficial cognitive effect in aging rats. The G. tsugae extract “significantly improved the locomotion and spatial memory and learning in the aging rats”. The extract also slowed the reduction of dendritic branching in neurons - i.e. it slowed neuron degradation.


These medicinal qualities will continue to be researched, but what’s most exciting is this medicine grows in our own woods and parks. Many of these compounds are water soluble so we can extract them from the mushroom just by drying it and then making tea. A powerful way to develop a relationship and reconnect with your local land.


Ganoderma tsugae
Young mushrooms will have a broad white margin with yellow, orange, and red forming toward the base.

Ecology

The fungus is saprobic, a decomposer of dead hemlocks and seldomly other conifers. G. tsugae can be found throughout the same range as the eastern hemlock - from Wisconsin over to Nova Scotia and down the Appalachian Mountains into northern Alabama. New fruiting bodies will appear in late spring and grow throughout the summer, often persisting over winter. Not just a decomposer though, it is also a composer of unique ecosystems for certain insects.


There are a couple of unique insects to look out for when you encounter G. tsugae or other Ganoderma species. Below is a pair of forked fungus beetles (Bolitotherus cornutus), a beetle that lives each stage of its life on or in Ganoderma fruiting bodies (fruiting body just means mushroom). The eggs are laid on the mushroom, the larvae burrow into and feed on the mushroom, and the adults emerge and mate on the mushroom. Adults can live up to eight years, and since the fruiting body will persist for a couple years on the same tree, the insect can spend consecutive years on the same mushroom.


Beetles mating
Usually active at night, we’re fortunate enough here to encounter these beetles during their elaborate courtship and mating behavior.

Another insect, the pleasing fungus beetle (Megalodacne heros) is also frequently found on G. tsugae fruiting bodies. This species is larger, with a "pleasingly shiny back", and each stage of life also involves the Ganoderma fruiting bodies. They can usually be found crawling on or near the fruiting bodies and are easier to find than the smaller, forked fungus beetles.


Beetle
M. heros crawling on the cap of G. tsugae. It’s common to find the mushrooms partially eaten and these large beetles are one of the culprits.

Alright, folks, we’ve been graced with plenty of rain and subsequently we’re starting to see plenty of mushrooms. I already have weeks of mushrooms lined up - should be a great summer.


Now time to watch Joey "Jaws" Chestnut in the Nathan’s hotdog eating contest,

Aubrey


References:

1) Kuo, M. (2019, January). Ganoderma tsugae. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/ganoderma_tsugae.html

2) Kuo HC, Tong SY, Chao MW, Tseng CY. Ganoderma tsugae prevents cognitive impairment and attenuates oxidative damage in d-galactose-induced aging in the rat brain. PLoS One. 2022 Apr 7;17(4):e0266331. doi: 10.1371/journal.pone.0266331. PMID: 35390035; PMCID: PMC8989198.

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