Although there’s not much new growth in the gardens in winter, as our damp mild weather continues, various species of fungi continue to pop up around the property.  This morning I found a small colony of Caulorhiza umbonata, also known as the ‘Redwood Rooter’ mushroom growing underneath a grove of coast redwoods  (Sequoia sempervirens) near the house.  This species was previously known as Collybia umbonata.


Caulorhiza umbonata

This mushroom species is typically found singly or in small clusters and fruits from early to mid-winter.  It is usually the only mushroom larger than 2 inches in diameter that is regularly found growing at the base of our decay-resistant coast redwood trees.


Caulorhiza umbonata

When these mushrooms first appeared, initially I presumed they might be a type of waxy cap mushroom, however, both the color, and variety of cap shapes throughout the lifestage of this species didn’t seem to fit with any of the waxy cap mushrooms I could find described.


Immature Caulorhiza umbonata with conical shaped cap

When young, it’s clear that the ‘Redwood Rooter’ has a conical cap shape, similar in appearance to Hygrocybe conica, or the ‘witch’s hat’.


The cap of Caulorhiza umbonata is conical in this newly emerging specimen

However, as this mushroom matures the cap becomes more umbonate in appearance.

The classically umbonate cap shape of a maturing Caulorhiza umbonata

As the mushroom ages further the cap margin curls upward, sometimes markedly so, as shown below.


The curled cap of a mature Caulorhiza umbonata (left) compared to the umbonate cap of a young specimen (right)

The name ‘Redwood Rooter’ refers to the tremendous length of the stipe, or stem.  Caulorhiza umbonata commonly roots one to three feet into the rich, acidic, deep humus found beneath the redwood trees.  The stem length above ground is perhaps only 2-4 inches, but the extent of the root below the soil surface is quite remarkable. I attempted to excavate a specimen with the entire stem intact, but unfortunately, despite my best efforts, I still managed to snap the last part of the stem.


Note the extensive length of the stipe in this species compared to the cap size.

This agaric, or gilled, mushroom species is quite large, and easily noticed underneath the redwoods where little else, other than moss and redwood sorrel, grows.


The creamy white gills are easily observed beneath the cap of mature specimens of Caulorhiza umbonata

The cap diameter for these specimens ranges from approximately 2 to more than 5 inches across in larger specimens.  As the margin of the cap everts, the beautiful gills beneath are revealed.


Mature specimen of Caulorhiza umbonata


The cap margin can become extensively ruffled in appearance

In addition to its association only with redwood trees here, the keys to identifying this species were its extensive ‘tap root’, pale gill color, cap shape (conical in immature specimens, and umbonate when mature), and its white spore print.

Caulorhiza umbonata produces white spores



An immature Caulorhiza umbonata nestled between two mature specimens

Little seems to be known in regards to toxicity for this species, but as the ‘Redwood Rooter’ is quite common in this part of Northern California at this time of year, mycologists presumed that Caulorhiza umbonata is not significantly toxic.

I wonder what other fabulous fungi we’ll find in our woods this winter?