The Lemon Yellow Lepiota – Leucocoprinus birnbaumii

Some mushroom species thrive in human-curated habitats, and the lemon-yellow lepiota, Leucocoprinus birnbaumii, is no exception. The lemon-yellow lepiota is one of those mushrooms that people constantly ask me to identify, because it is exceedingly common in flower pots and other planters in subtropical environments, and it is flashy enough that you simply cannot help but notice it, even though the mushroom itself is quite small. Unlike some mushrooms that you have to head into the woods to spot, this dainty, “civilized” little mushroom is more likely to show up in your windowsill planter box or garden, rather than hiding in deep forest or wild meadow habitats.

Leucocoprinus birnbaumii with succulents
The lemon yellow lepiota, Leucocoprinus birnbaumii, growing in gravel and potting soil alongside succulents. Note the pale yellow color, parasol-shaped cap with stripy striations, and the ring on the upper portion of the stalk. Photo by Anna McHugh.

Features of the Lemon-Yellow Lepiota

The lemon-yellow lepiota favors habitats that we create for our plant friends; they sprout up in flower pots, greenhouses, and planter boxes with almost alarming frequency, and their bright coloration and shapely form is hard to miss. Even though the name “lemon-yellow lepiota” offers a fairly good description of the mushroom’s appearance, it creates a little confusion about this species’ genetic roots (it is not a member of the Lepiota genus at all, although an alternate, older name for this mushroom places it in the genus with the Latin epithet Lepiota lutea). For this reason, combined with my love for whimsy, makes me prefer the mushroom’s alternate common name, the plant-pot dapperling.

The lemon-yellow lepiota is a classic cap-and-stem mushroom with delicate, tightly packed gills underneath a parasol-shaped cap. It rarely gets taller than a few inches in height, and is quick to sprout and equally fast-fading. The entire life-cycle of the mushroom last only a couple days, depending on the weather. Since these mushrooms do pretty well in warm weather but also require a good bit of moisture to stay fresh and happy, a turn towards dry weather will make them vanish almost immediately.

Although the common name in wide circulation in North America pegs it to the Lepiota genus, the lemon-yellow lepiota mushroom is not as closely related to the parasol mushrooms (such as the shaggy parasol, Chlorophyllum rhacodes) as it is to mushrooms in the genera Coprinus and Coprinopsis. Like the coprinoid mushrooms, Leucocoprinus birnbaumii is a decomposing mushroom, meaning that its mycelium feeds off compost and other dead organic material in its habitat. This mushroom’s color, combined with its habit of settling in potted plants, makes it fairly easy to identify. The mushroom has an undeniably cheerful hue, with a color ranging from vibrant, almost canary yellow to pale, daffodil yellow. In addition to its parasol-like shape, the lemon-yellow lepiota’s cap has scurfy bits of flesh that look and feel powdery or flaky. The center of the cap is typically adorned with a small, darker-colored nubbin once the mushroom reaches maturity. In its early stages, the mushroom looks like a small club on a slender stem, with the cap attached to the stem by a partial veil. As the mushroom ages, the cap opens and breaks the partial veil, leaving a fragile yellowish-brown ring on the stalk.

Leucocoprinus birnbaumii
The lemon yellow lepiota, Leucocoprinus birnbaumii. Note the fuzzy yellow tissue sticking to the cap and the darker coloration of the central knob of the cap. Photo taken (in really poor light) by Anna McHugh.

In nature, the lemon-yellow lepiota grows in the tropics. In Europe and North America, it’s most commonly spotted in hothouses in cooler climates, and is very common outdoors in the southeastern United States, Texas, and other places where there are periods of hot, humid weather. They typically come around in late spring and summer, and seem to spring out of potting soil with an enthusiasm that’s astonishing; they go from tiny little yellow club-lumps of fungus to 3- or 4-inch mushrooms in no time flat. Sadly (at least for me, because I like them), lemon-yellow lepiotas disintegrate just as swiftly, although they do not turn into the slimy pile of goo that’s the inevitable end of their relative the shaggy mane, Coprinus comatus

Lemon-Yellow Lepiota Edibility: Nope

The lemon-yellow lepiota is poisonous and should not be eaten. Hopefully, this won’t even tempt you; it’s just such a wee little thing that you’d be hard-pressed to get even a mouthful anyway, even if you were to pluck and entire patch of these gregarious little monsters. Although it is considered a toxic mushroom, there is little to suggest that they are a dangerous mushroom to have around.

Unlike some mushrooms, like the death cap, Amanita phalloidesthere is not much in the literature and anecdotal information I have gathered to suggest that pets are at high risk for consuming them (unfortunately, some dogs in particular have a taste for mushrooms and can be sickened by consuming poisonous species).

Lemon-Yellow Lepiota Eradication: Why Bother?

Sometimes, I hear from distressed gardeners who worry that the profusion of lemon-yellow lepiotas they just discovered will somehow harm their plants. Not to fear! Since this little mushroom is a decomposer and is not parasitic, it is no cause for alarm. Furthermore, since it is fragile and frail, you’re unlikely to see them stick around for any length of time; they’re one of those “here today, gone tomorrow” mushrooms that isn’t large enough to make a mess even when it does decompose. Best to just leave them alone, and not worry about ’em!


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