Omphalotus olearius

Description

This mushroom is quite noticeable due to its color, size, and occurrence in clusters near trees or stumps. It is most commonly found in the forest or natural areas, sometimes in landscapes. It appears in clusters of up to 15-20 mushrooms usually at the base of a living oak or from stumps or buried wood (roots), occasionally on other deciduous trees.

Omphalotus olearius glows in the dark. Not the whole mushroom, but just the gills on the underside of the mushroom. If you find these mushrooms, take them into a very dark room and stare at the gills of the fungus until your eyes become acclimated to the dark - you should see an eerie greenish glow emanating from the fungus.

This mushroom contains the toxin muscarine, which causes severe cramps and diarrhea. It is not deadly, but consuming this species may require hospitalization.

Common names: Jack-O'-Lantern Mushroom.

Mushroom Identification

1. Ecology

   Saprobic; growing in large clusters on the stumps or buried roots of hardwoods, especially oaks and olive; late summer and fall; central and southern Europe.

2. Cap

   4-12 cm; at first broadly convex, but soon becoming shallowly to moderately depressed; not usually featuring a central bump; bald; dry or slightly greasy; bright brownish orange to yellowish orange - or in some collections reddish-orange or nearly brown; the margin slightly inrolled when young.

3. Gills

   Running down the stem; close; orange; with many short-gills; luminescent when fresh.

4. Stem

   3.5-9 cm long; 1-2 cm thick; tapering to base; solid; bald; pale orange to orange.

5. Flesh

   Pale orange; unchanging when sliced.

6. Spore Print: Whitish.

History

This saprobic mushroom was described in 1815 by Augustin Pyramis De Candolle, who gave it the binomial scientific name Agaricus olearius. (Most gilled fungi were initially placed in a giant Agaricus genus, now mostly redistributed across many other newer genera.) The currently accepted scientific name Omphalotus olearius dates from a 1946 publication by the German-born mycologist Rolf Singer.

Synonyms of Omphalotus olearius include Agaricus olearius DC.

The genus name Omphalotus means umbilicate (in the form of a navel), and refers to the central depression in mature caps, as seen in the picture above. You may be pleased to know that the specific epithet olearius is not a reference to Ryanair's chief executive Michael O'Leary or any other member of the O'Leary clan; olearius means 'of the olive tree' - and indeed it is with olive trees that this saprobic mushroom is nearly always associated, at least in southern Europe.

Confusingly, some people refer to this mushroom as Jack o' Lantern - a common name it, therefore, must share with Omphalotus illudens with which it was considered conspecific until recent studies convinced most authorities that although macroscopically inseparable the two are indeed quite distinct species.

Photo sources:

Photo 1 - Author: Dimitǎr Boevski (CC BY-SA 4.0)

Photo 2 - Author: zaca (CC BY-SA 3.0)

Photo 3 - Author: Antonio Abbatiello (Public Domain)

Photo 4 - Author: danhartleybcn (Public Domain)

Photo 5 - Author: danhartleybcn (Public Domain)