Midwest

American

Mycological

Information

Armillaria mellea,
Armillaria tabescens, Armillaria bulbosa

Armillaria mellea

Common name: Honey Mushroom, Stumper, Bootstrap Fungus

Description and identifying characteristics: Armillaria species are commonly referred to as “Honey Mushrooms” due to the yellow-brown color of their caps, which are often sticky to the touch when moist. Honey Mushrooms display a cespitose pattern of growth, where they grow in dense clumps or tufts, with the stems of the individual mushrooms, tapering and joining together at the base. Clumps of Honey Mushrooms may contain up to 50 mushrooms, although clusters of 10-20 are more common. Armillaria species fruit primarily in the fall, although they may be seen in late summer after heavy rains.

All species of Armillaria except A. tabescens have an annulus (i.e. ring) around the stalk (see the top-left and middle-right photos below). The annulus is the remnant of a veil that attaches from the stem to the cap, but is torn away from the cap while remaining attached around the stalk like a skirt as the mushroom matures.

Caps of Armillaria species vary in size, ranging between 3-15 cm on average when mature. They will sometimes have a few, tiny, dark scales concentrated near the center-top of the cap, arranged radially outward. The gills are attached or somewhat decurrent (running slightly down the stem), and the spore print of this mushroom is white. The stems can be tough and fibrous.

Ecology/Associated Habitat: Ecologically, Armillaria species function as parasites of living hardwood trees (although they may rarely be seen growing on conifers), where they cause an intensive white-rot of their host. They also can function as saprotrophs and are involved in the decomposition of dead hardwood logs, stumps and roots (hence the common name, “stumpy”), recycling these nutrients back into the environment. As a parasite, Armillaria species can be invasive and devastating to a forest, moving tree to tree via thick, black, cord-like structures called rhizomorphs, slowly girdling an killing their tree hosts. After killing the trees, Armillaria species may continue to live saptrophically on the remains of the trees. Single Armillaria individuals have been shown to extend miles across via mycelial network below ground, with ages estimated at 1000s of years.

Poisonous look-alikes: Some Pholiota species, which also arise in cespitose clusters from wood in the fall, may be mistaken for Armillaria species at first glance, but are easily distinguished as Pholiota species, which have a yellowish to greenish yellow cast and a dark brown to grey-brown spore print (in contrast to the white spore print of Armillaria species). Deadly Galerina species, which can grow side-by-side Armillaria on wood, are easily distinguished by their rusty-brown spore prints.

Armillaria species can also be mistaken for young, poisonous Jack-O-Lantern mushrooms (Omphalotus illudens) which may also grow in cespitose groups at the base of hardwood trees, stumps or buried roots. The Jack-O-Lantern can be distinguished from Armillaria species by its dry, smooth, wavy-lobed orange to yellow-orange cap and its yellowish spore print.

Methods and Tips on harvesting: Honey Mushrooms are best cut at the base of the stipe with a sharp knife or scissors. Large scissors are good for harvesting large, tightly-bound clusters. Since these mushrooms often grow from the ground arising from buried roots or next to hardwood stumps, it is a good idea to have a soft-bristled brush (such as a small, unused, clean paint brush) handy to remove excess dirt, sand or other debris before placing them in your collection basket.

As with other mushrooms, younger buttons (before the caps flatten out) are the most choice specimens for cooking. Older specimens are also acceptable if firm and in good condition. The stems can be fibrous and woody, but may still be used in soups and sauces if peeled and minced.

Given their parasitic and saprotrophic ecology, Honey mushrooms will kill and eat large trees, thus they appear in the same spot, arising from the same substrates (e.g. trees, stumps, roots), year after year. It is, therefore, advised to mark the position where you found them growing (with a GPS if available) so that you may easily return to the same spot in following seasons.

Possible allergic reactions and symptoms: A small percentage of people may be sensitive to certain species of Armillaria. This can be overcome by cooking them well, so we recommend you thoroughly cook these mushrooms before serving. As with any wild edible fungus, only try small amounts at first, do not try more than one new species at a time.

Special considerations for storage. As with all other mushrooms, store Honey Mushrooms in containers that allow the diffusion of gas (such as paper or cloth bags). Never store any portion of this or any other mushroom in an airtight container such as a zip-lock bag

Photos:

Armillaria mellea
Armillaria mellea

Armillaria displaying cespitose grouping

Armillaria mellea
Armillaria mellea

Some morphological differences

Armillaria mellea
Armillaria mellea

Armillaria parasitizing living trees

References:

Michael Kuo. Armillaria melea

Key to North American Armillaria species from Tom Volk

Tom Volk’s fungus of the month, April 2002

Steve Brill

Armillaria melea at Mycoweb

Armillaria melea at Roger’s Mushrooms