The Reality of Blue Mushrooms
The natural world often presents surprising colors, and mushrooms are no exception. Many wonder if truly blue mushrooms exist, given the common earthy tones of fungi. Blue mushrooms are indeed a reality, showcasing hues from subtle blue-greens to deep indigos. Their vibrant coloration makes them stand out in various ecosystems worldwide. While not as common as brown or white varieties, these fungi add to the remarkable diversity of the fungal kingdom.
Common Blue Mushroom Species
Numerous blue mushroom species inhabit different environments, each with unique characteristics. One prominent example is Lactarius indigo, commonly known as the Indigo Milk Cap or Blue Milk Mushroom. This species is widely distributed across eastern and southwestern North America, East Asia, and Central America, often found growing on the ground in deciduous and coniferous forests.
Lactarius indigo features a cap that can range from dark blue in fresh specimens to a pale blue-gray as it ages, typically measuring 4–15 cm (2–6 in) in diameter. A distinctive feature is the indigo blue milky latex it exudes when its tissues are cut or broken, which slowly turns green upon exposure to air. The gills are also indigo blue and are closely arranged.
Another notable blue mushroom is Gyroporus cyanescens, known as the Bluing Bolete or Cornflower Bolete. This species is found in Eurasia, Australia, and eastern North America, typically growing in coniferous and mixed forests. Its yellowish to buff cap, up to 12 cm (4.7 in) in diameter, and thick stem, often hollowed into chambers, turn an intense blue color within moments of bruising or cutting. This dramatic color change is a key identifying feature.
The Blue Roundhead, Stropharia caerulea, is another blue-green specimen commonly found across temperate regions of Europe and North America. Its cap, initially bell-shaped and blue-green, becomes broadly bell-shaped or convex as it matures and can be slimy when fresh. As it ages, the cap may fade to yellowish-green.
Additionally, the Pixie’s Parasol, Mycena interrupta, is a small, fragile, blue mushroom found in southeast Australia, New Zealand, New Caledonia, and Chile. These tiny mushrooms have cyan-blue caps, up to 0.75 inches across, that are initially spherical and become broadly convex, often with a slightly depressed center. The Blue Oyster Mushroom, Pleurotus columbinus, is a cultivated variety that also occurs naturally in temperate forests globally.
What Makes Mushrooms Blue?
The blue coloration in mushrooms can arise from different chemical processes. In many species, particularly those that bruise blue, the color change is often a result of oxidation reactions. For instance, in Psilocybe mushrooms, which are known for their psychoactive compounds, bluing occurs when psilocybin is converted to psilocin, which then oxidizes upon exposure to air. This oxidation leads to the formation of blue quinoid psilocyl oligomers. These blue compounds are structurally similar to indigo, the dye used in blue jeans. This bluing reaction is thought to serve as a defense mechanism against insect predation.
Not all blue-staining mushrooms achieve their color through the same chemical pathway. In some boletes, like Gyroporus cyanescens, the blue color results from the enzymatic oxidation of a compound called gyrocyanin, which is not psychoactive. Other boletes may turn blue due to the oxidation of various acids. These chemical reactions are sensitive to air exposure, explaining why the blue color often appears rapidly when the mushroom is cut or bruised.
Some mushrooms, such as Lactarius indigo and Entoloma hochstetteri, owe their inherent blue color to specific pigments. Lactarius indigo contains an organic compound called methyl stearate, which contributes to its distinct blue hue. Entoloma hochstetteri, native to New Zealand, gets its blue color from azulene pigments. Azulene is an aromatic organic compound known for its dark blue color.
Safety and Identification Considerations
Encountering a blue mushroom in the wild can be exciting due to their striking appearance, but it is important to approach wild mushrooms with caution. The edibility and toxicity of blue mushrooms vary widely, and color alone is not a reliable indicator of whether a mushroom is safe to consume. Many blue mushrooms are poisonous, and some can cause significant health issues if ingested. For example, while some blue-staining boletes are edible after proper preparation, others, such as Boletus satanas, are highly poisonous.
Accurate identification is essential before considering any wild mushroom for consumption. Relying on visual cues alone can be misleading, as some toxic species may resemble edible ones. It is advisable to consult multiple reliable field guides specific to your region and to learn about the mushroom’s habitat, spore print, cap shape, gill structure, and any characteristic bruising or milky latex. Joining a local mycological group or seeking guidance from an expert mycologist can provide valuable hands-on training and reduce the risk of misidentification.
Never consume a wild mushroom unless its identification is certain and confirmed by an expert. The general advice for mushroom foraging is to avoid consumption of any species you are not confident in identifying. Prioritizing safety over curiosity when encountering wild fungi is important.