Macrocybe titans

🏷️ Description

Imagine walking through a grassy field and stumbling upon a mushroom so large that it could double as an umbrella. Meet Macrocybe titans, the largest known gilled mushroom in the Western Hemisphere! With caps that can stretch over 100 cm (3 ft) across and stems that tower up to 40 cm (16 in) tall, this colossal fungus is truly a marvel of nature.

Originally described as Tricholoma titans in 1980 by Howard E. Bigelow and J. W. Kimbrough, this giant was reclassified into the genus Macrocybe in 1998. Its name literally translates to "giant head," an apt description for a mushroom of such monstrous proportions.

🌡️ A Mushroom on the Move? Historical records suggest that M. titans may not have always been present in the southeastern U.S. Some mycologists hypothesize that it was introduced from the Caribbean and has been slowly expanding its range due to human activities (such as soil and mulch transport) and climate change. With warming temperatures, its distribution could extend even further north in the coming years.

🌎 Where to Find

First discovered in Gainesville, Florida, this species has since been spotted across the southeastern United States, including Georgia, Louisiana, North Carolina, South Carolina, and Texas. It thrives in the tropics and subtropics, with sightings reported in Mexico, Belize, Costa Rica, Panama, Puerto Rico, Trinidad, Argentina, Brazil, Colombia, Ecuador, and Venezuela. Often found in disturbed areas such as roadsides, near buildings, and grassy fields, this species seems to have adapted well to human-altered landscapes.

🔎 Identification

This mushroom is unmistakable due to its sheer size and unique features:

• Cap: Ranges from 3.15 to 39.4 inches (8–100 cm), pale buff to cream-colored, convex when young but flattens with age.

• Gills: Crowded, sinuate (notched), white to pale grey or brown.

• Stem: Thick and robust, reaching 6–38 cm in height, with a swollen base up to 12 cm in diameter.

• Spore Print: Creamy white.

• Odor: Mild and nondescript.

• Microscopic Features: Presence of pseudocystidia and clamp connections, with spores measuring 5–7 x 4–5 µm.

🧬 Ecology and Role

M. titans is saprobic, meaning it feeds on dead plant material. As a decomposer, it plays a vital role in breaking down organic matter and cycling nutrients back into the ecosystem. Unlike some fungi that form symbiotic relationships with plants, M. titans does not associate with tree roots (mycorrhizae) and is not parasitic.

🍽️ Edibility

Can You Eat It? There are reports that M. titans is edible, but extreme caution is advised. Misidentification with poisonous mushrooms like Chlorophyllum molybdites (the green-spored parasol) could lead to serious illness. If you’re not a mushroom expert, it's best to admire this titan from a distance. As the saying goes: When in doubt, throw it out!

Photo sources:

Photo 1 - Author: Pedro Henrique Maloso Ramos (CC BY 4.0)

Photo 2 - Author: Douglas Lopes (CC BY 4.0)

Photo 3 - Author: Denis Zabin (CC BY 4.0)

Photo 4 - Author: Scott Allen Davis (CC BY 4.0)