When the arrowleaf balsamroot is blooming, it is time for lightning mushrooms. 

When you are out walking in the grasslands and sagebrush areas around Kamloops this spring, be on the lookout for circles of a large, white mushroom. These are lightning mushrooms, one of the few large mushrooms that occur in spring around Kamloops. It’s gone by various genera, including Calocybe, Lepista, and Tricholoma, but the genes have been sequenced and it is now known as Leucocalocybe mongolica in the family Lyophyllaceae. Originally described from East Asia, it is well known as an edible in Mongolia, Northern China, and Eastern Russia. Their presence in Europe has been documented for hundreds of years. They are well known by our local native bands and recognized as a high-quality edible mushroom.

In the book, Mushrooms of British Columbia, the authors note that thunder and lightning have a long history with mushrooms and fairy rings (circles of mushrooms). Greeks and Romans thought that mushrooms were produced by thunder and the grandfather of Charles Darwin, Erasmus, made a connection between lightning and fairy rings. The notion is not entirely implausible. There is experimental evidence that applying an electrical current to mycelium can sometimes stimulate mushroom fruiting. The Nlaka’pamux (Thompson) First Nation in the Southern Interior call them “thunderstorm head” or “lightning mushrooms.”

Arc of lightning mushrooms in Lac du Bois (G. Hunt photo)

Note the white cap and gill colour (G. Hunt photo)

In the button stage, the cap begins to split (G. Hunt photo)

In North America, they occur primarily in northern latitudes and have not been reported in Washington, Oregon, or California. They have been reported in Montana, Wyoming, Idaho, and Colorado. They occur in arid grassland communities in Western Canada. Locally, they occur at mid-elevations (500-1000m) in Lac du Bois, along Lac Le Jeune Road, and between Kamloops and Cache Creek.

The ecology of these mushrooms is interesting. They occur in open grasslands and damp meadows, and in sagebrush ecosystems. You would never find them in a closed forest. The reason they form circles (“fairy rings”) is that the main body of the fungus lives in the soil as microscopic threads of cells called hyphae. The circular mass of hyphae is called the mycelium or “shiro.” A shiro starts from the germination of spores and spreads in a circle from one starting point. As a saprophytic species, the mycelium consumes organic matter and produces mushrooms on the outer-most, leading edge of the circle. Look for them when the arrowleaf balsamroot is blooming.

The darker green grass indicates the roughy circular fungal mycelium (G. Hunt photo)

Notice in the picture that the mushrooms form a broad arc. To the right side of the mushrooms, you can see that the vegetation is darker green and this zone forms an irregular circle. This dark green zone indicates where the mycelium is present. The plants are greener because the fungus is breaking down organic matter and releasing nutrients into the soil. The diameter of this circle is 8 or 10 m across. The presence of mushrooms on one side of the shiro indicates that the soil is more nutrient rich on that side.

How many years has this shiro been growing? Unless we were to measure how far the arc of mushrooms moves yearly for several years we cannot know for sure, however, we can make a rough guess. Years ago, a mycologist in Williams Lake estimated the outward mushroom migration on shiros in that area was about 10 cm per year. Assuming a constant growth rate (quite a big assumption!) and the current diameter of about 8 m, this shiro may have started about 80 years ago or sometime in the 1930s.