If you have ever walked through a forest after the rain and suddenly spotted something that looked like an alien egg cracking open on the ground, there is a good chance you encountered a stinkhorn mushroom. Known scientifically as Phallus impudicus and commonly referred to as the “stinkhorn,” this bizarre fungus has earned a reputation as one of the most frightening-looking organisms in the natural world. But what exactly is it, and why does it evoke such strong reactions from anyone who sees or smells it?

A Strange Life That Begins as an Egg

The life of a stinkhorn mushroom starts with a stage that confuses even experienced foragers: the “witch’s egg.” This rounded, rubbery structure sits partially buried in soil or grass, resembling a mysterious biological pod. When sliced open, it reveals a gelatinous interior and a folded structure that will later become the mushroom’s mature form. Many people describe this stage as looking like an alien embryo or a scene from a sci-fi movie, and it’s easy to understand why.

Within just a few hours—sometimes overnight—the egg splits open dramatically. From inside, the mushroom’s tall, sponge-like stalk emerges, growing at a surprisingly fast speed. Some stinkhorns can shoot up several inches in a single morning, making them one of the fastest-growing fungi on the planet.

The Infamous Smell: Why It Stinks Like Rotting Flesh

The shock of seeing a stinkhorn is nothing compared to the moment you smell one. As soon as the mushroom reaches maturity, it releases a foul odor that many describe as a mix of rotting meat, sewage, and decomposing animals. This unpleasant scent is not an accident—it’s a survival strategy.

Unlike many mushroom species that rely on wind to spread their spores, stinkhorns use insects. The slimy, dark cap at the top of the mushroom is coated with a substance called gleba, which contains both spores and the unmistakable smell. Flies, beetles, and other scavenging insects are attracted to the scent, land on the cap, and unintentionally carry the spores with them as they fly away. In other words, the stinkhorn’s revolting odor is actually a sophisticated biological method of reproduction.