Mystery of the Unknown Baldcypress Fungus

Forrest M. Mims III

The baldcypress (Taxodium distichum) is a large and stately tree native to river bottoms and swamps in the Southeastern United States and Mexico. While three species have long been recognized by botanists, molecular biologists generally believe all are varieties of the same species.

Some baldcypress are among the oldest North American trees. Their wood is prized for its beauty and its resistance to rot and decay.

The resistance of the baldcypress to invasive attack by fungi does not extend to Stereum taxodi. This fungus enters the crown of the tree and works it way down through the trunk. It may cause large trees to develop hollow cavities. It also leaves behind decorative patterns and holes known as pecky cypress, which is prized by cabinet makers.

A few fungi attack the needles of baldcypress, but a literature search has revealed no other fungi that attack baldcypress.

That's why I was recently surprised to find scores of fungus fruiting bodies emerging from the knees and the base of the trunk of one of three baldcypress growing along our stretch of Geronimo Creek. Their caps and stipes (stems) were cream white and appeared to decorate the base of the tree.

I photographed the specimens using a Pentax Optio 43 WR water resistant camera. This permitted closeups to be made while the bottom of the camera was immersed in the creek.

Figure 1 shows some of the fungi, which are clearly emerging from the living wood of the baldcypress.

Figure 2 shows the underside of the largest cap with the gills clearly visible.

Figure 3 is a microphoto that shows spores emerging from the edges of a gill. The emergence of the fungus all around the base of the trunk and the knees of the cypress suggests that the spores might be transported by water.

Shortly after these photos were made, a rise on the creek from welcome summer showers washed away all the white gill caps. But within a week, many more replaced those that were lost. They lasted about ten days before disappearing.

Dr. Donald Pfister is a renowned fungus expert. He is the Asa Gray Professor of Systematic Botany at Harvard University. He is also Interim Director of the Harvard University Herbaria and Curator of the Farlow Herbarium. I sent Dr. Pfister photos of the baldcypress fungus, and he was unable to identify it or find a reference to it in the baldcypress literature he consulted. He suggested that it might be a Mycena sp., some species of which grow on living trees. He forwarded my inquiry to Dr. Brian Perry, who suggested that the morphology of the unknown fungus looks more like a Hemimycena than Mycena. The single photo of a Hemimycena that I found confirms the latter impression.

When the identity of this mysterious fungus is confirmed and its strange presence on a living baldcypress is explained, I'll report back the details. Meanwhile, this story again affirms that there is much in the natural world yet to be discovered, and that citizen scientists have a role to play.

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