#181: Chlorophyllum molybdites

Happy St. Patrick’s Day! To celebrate, I chose to discuss the Green Spored Lepiota, Chlorophyllum molybdites (I will return to morphological groups of agarics next week). Commonly known as the “Green Spored Lepiota,” the “Green-Gilled Lepiota,” the “False Parasol,” and various derivatives of those names, C. molybdites is the most common culprit in cases of mushroom poisoning in the United States. The large, attractive mushrooms frequently appear in lawns, making them prime candidates for consumption by people who aren’t familiar with mushrooms. Thankfully, the mushroom causes only gastrointestinal (GI) distress. People wishing to avoid this unpleasant experience can easily recognize C. molybdites thanks to its green spores.

^1–3

Description

As hinted at by its common names, C. molybdites is a lepiotoid mushroom (FFF#???): it has a circular pileus, a central stipe, free gills, and a partial veil. C. molybdites is large for a lepiotoid mushroom, growing 5-25cm tall and 5-30cm wide.^3–5

The pileus of C. molybdites is fairly distinctive. When young, it is spherical and pinkish to brownish, but as the mushroom grows the outer layer cracks apart to reveal a white surface below. Mature mushrooms have a pileus that is convex to flat, white, and dotted with pink to brown scales. The scales are irregularly distributed across the pileus and the spacing usually decreases toward the center, where they coalesce to form a solid disc of darker tissue.^3–5

Underneath the pileus, the spore-producing surface is arranged into gills that radiate out from a central stipe. Like other lepiotoid mushrooms, the gills are free from the stipe or barely attached to it. Young mushrooms have white gills, but the gills slowly darken and usually take on a grayish brownish green by maturity. This is the most useful feature for identifying the Green Spored Lepiota. C. molybdites is the only lepiotoid mushroom in North America with greenish gills at maturity; if your mushroom’s gills have a distinctly green tint, you can be sure of your identification. The gills adopt a greenish color because they produce green spores. If you can’t decide whether your mushroom’s gills are green, taking a spore print will normally give the answer.^3–5 Sometimes, the Green Spored Lepiota takes a very long time to start producing spores or produces mostly white spores, which can wreak havoc with identification efforts.¹ For best results, make sure you take the spore print of a fully mature specimen.

For supporting such a large pileus, the stipe is surprisingly thin and dainty. It is white and sometimes features tiny hairs or scales. The stipe is equal in width for the most part, but often tapers slightly toward the top and expands slightly toward the base. Near the top of the stipe, you will find the most interesting feature of the stipe: the ring. Before the mushroom’s gills are ready to produce spores, they are covered with a thick, white membrane called a partial veil. As the mushroom matures, the membrane breaks apart and exposes the gills. The bulk of the partial veil collapses around the stipe to form the ring; a few remnants may also be found clinging to the edge of the pileus. The ring is thick and persists well into maturity.^3–5

Ecology

C. molybdites is a common sight in North American meadows and lawns from spring through fall.^3–5 I usually find these mushrooms during hot weather following heavy rain. For my area, this means I am most likely to find them in September and October, although they can fruit during other months as well.

The mushroom’s habitat is another feature that sets it apart from most lepiotoid mushrooms. All lepiotoid fungi, including C. molybdites, are saprobic. However, most of them decompose forest litter, mulch, and other such debris. C. molybdites, on the other hand, is always found in meadows and lawns.^3–5

Although the Green Spored Lepiota can produce a solitary mushroom, it is more likely to produce several mushrooms in a small area. The fungus also frequently pushes up mushrooms in a fairy ring.^1,4 This ecology is particularly well suited to suburbia, and this mushroom commonly pops up in peoples’ yards. Unfortunately, this raises the likelihood that someone will accidently eat it.

Toxicity

The Green Spored Lepiota is the worst GI irritant mushroom. In fact, the symptoms are different enough from those produced by other GI irritant mushrooms that the North American Mycological Association’s webpage on mushroom toxins lists C. molybdites separately (see this page).² Symptoms appear between one and two hours after eating the mushroom and can include: nausea, dizziness, vomiting, abdominal pain, and diarrhea. These symptoms can vary in severity due to differences in weather, individual mushrooms, and each person’s age and sensitivity.⁶ In the worst cases, sufferers can have bloody, explosive diarrhea and may need hospital treatment. The toxin(s) involved are not yet known, so treatment of C. molybdites poisoning focuses on alleviating symptoms: doctors administer drugs to counteract the vomiting and diarrhea and administer fluids and electrolytes when necessary. One of the greatest dangers with this type of poisoning is dehydration, so staying properly hydrated is paramount. The only known fatality from the Green Spored Lepiota was a child, which is not surprising because children are more likely to eat unknown mushooms and because they are smaller and therefore more sensitive to toxins than adults are.^1,6

Similar Species

There are a few other species that can be confused with C. molybdites. The two closest in appearance are C. rhacodes and C. brunneum. These two fungi belong to the same genus as C. molybdites and are nearly identical to that mushroom when young. Neither C. rhacodes nor C. brunneum has green spores, which should easily tell the mushrooms apart… at maturity. If you can’t get a spore print, you may have to spend some quality time with a field guide before you can confidently put a name to your specimen.^4,5

Parasol Mushrooms like Macrolepiota procera can also be confused the Green Spored Lepiota. M. procera (the “Parasol Mushroom”), or whatever version of that species exists in America, can be distinguished by its snakeskin-like pattern on the stipe and its usual preference for forest habitats. Still, it is close enough in appearance that you should check to make sure your specimen does not have green spores.⁴

Some Amanita species also resemble C. molybdites,⁴ but no amanitas produce green spores. Additionally, the bumps of tissue on top of an Amanita pileus slough off easily whereas the scales of C. molybdites are attached to the pileus.

Taxonomy

You may have noticed the word ‘chlorophyll’ in the name Chlorophyllum molybdites. There is a good reason for this: chlorophyll is derived from the words ‘chloro’ meaning ‘green’ and ‘phyllum’ meaning leaf.¹ Chlorophyll is so named because it is the substance that turns plant leaves green. Similarly, the name Chlorophyllum denotes the green gills of C. molybdites (taxonomists don’t have a separate word for ‘mushroom gills’, so they just use the word for ‘leaves’).

The classification of C. molybdites, like that of many agarics, has changed a lot over the years. Most significantly, it once belonged to the genus Lepiota.⁷ Its common name – the “Green Spored Lepiota” – was established at that time. The name used publicly for this mushroom has not changed since, even after mycologists reassigned it to Chlorophyllum. C. molybdites is now just one of a multitude of mushrooms whose common names reflect outdated taxonomy.

Kingdom	Fungi
Division	Basidiomycota
Subdivision	Agaricomycotina
Class	Agaricomycetes
Subclass	Agaricomycetidae
Order	Agaricales
Family	Agaricaceae
Genus	Chlorophyllum
Species	Chlorophyllum molybdites (G. Mey.) Massee7