Lycoperdon umbrinum belongs to the group of fungi known as puffballs.

Lycoperdon umbrinum

This is a blackish puffball often misidentified as Lycoperdon nigrescens. The primary external difference between the two species is that Lycoperdon umbrinum has an exoperidium composed of very short stubble-like spines that are less than 1 mm in length, whereas L. nigrescens spines are more than 1 mm long.

Lycoperdon umbrinum has very short spines compared to L. nigrescens

Lycoperdon nigrescens has a more northerly distribution, found primarily in Idaho, Oregon, and Washington, and perhaps extreme northern California.  In this region, L. nigrescens is rare.  As these specimens were found in Santa Cruz county, and the spines are clearly shorter than 1 mm, these specimens appear to be L. umbrinum.

Lycoperdon umbrinum is recognized by the globose fruiting body, which averages 2.0-5.0 cm tall, and 2.0-4.0 cm wide.  This species is somewhat pear-shaped and unlike some puffballs, which lack a stem-like structure entirely, this species tapers below to a well developed ‘pseudostipe’ or stalk.  This is an extension of the spongy internal tissue, rather than a true stalk like those seen with gilled mushrooms. The exoperidium is colored dark-brown to blackish-brown, with short spines typically less than 1 mm in height.

Small wart-like structures may also be visible in younger specimens toward the apex.

Note the wart-like structures along the pseudostipe in this young specimen

As previously mentioned, this is not a gilled species of mushroom.  Instead, spores are formed internally in the sponge-like tissue in the spherical head of the puffball.

Cross section of Lycoperdon umbrinum showing spores that are forming in the spongy tissue

As this fungus matures, the spores are later released through a dorsal pore that develops in the exoperidium.

A young specimen with no pore visible in the 'cap'

A mature specimen showing the dorsal pore through which the fungal spores are released

Lycoperdon umbrinum is found singly or widely scattered on soil or duff in hardwood and conifer woods.  A number of these puffballs have been sighted sparsely scattered around our property, and one colony appears to be favoring the base of a giant Douglas fir tree overlooking the creek.  Thus far this is the only species of puffball that has been observed here, but who knows what else our wet winter will bring?

Tomorrow we’ll wrap up ‘mushroom week’ with something from another large group of fungi known as polypores.