Sulfer Shelf, by Martin Holden

The Sulfur Shelf, First Mushroom of the Season by Martin Holden, October 1, 2005

The sulfur shelf is one of the most conspicuous mushrooms found in the East Bay Hills. Sulfur shelves begin to sprout from stumps and on older, weakened or burned trees, particularly eucalyptus, in early October before the fall rains have come. Typically, the mushrooms begin as small efflorescences, like bright yellow marshmallows. Given time, they may grow into huge multi-tiered clusters weighing twenty pounds or more.

Sulfur shelves (Laetiporus gilbertsonii, recently separated from L. sulphureus on the West Coast) are polypores, shelf-like fungi that have small pores on their undersides, rather than gills. Their most conspicuous feature is their bright yellow color (sometimes banded with orange); hence the name. This fungus takes advantage of the moisture and sugars from dead and dying trees, which is why they flourish when everything else is dry. Like many other fungi, they provide an invaluable service by helping to decompose wood, returning its valuable nutrients to the soil.

Last fall, several big, black stinkbugs took up residence on a large sulfur shelf growing on a stump near the Clark Kerr Campus. They lived there happily for two months, eating the succulent fungus and lolling in the sun, in a luxurious beetle heaven. It reminded me of a story in Steinbeck’s Cannery Row, where Doc wonders if stink bugs are praying when they stick their hind ends in the air (as they often do). Now I think that they are praying— for a big, beautiful L. gilbertsonii to call home.