Many people are are hesitant to deal with the kingdom of fungi, and this is entirely justified. Identifying mushrooms is truly a difficult task, and overconfidence can have fatal consequences. So, what makes identification so challenging?

1. Vast Species Diversity

There are over 15,000 known species of macromycetes — the fungi that produce large fruiting bodies, commonly referred to as mushrooms. Many of these species are poorly documented and not well studied, and countless others are yet to be discovered.

Whether you live in hot Mexico or chilly Sweden, thousands of mushroom species grow around you, and it takes considerable effort to confidently identify even the most common ones.

2. Look-Alike Species

With such a wide variety of species, it's almost inevitable that nature will repeat some of its designs. The resemblance between closely related species shouldn't be surprising and is often expected, though mistaking one for another can still be unpleasant. All species of Agaricus (of which at least several dozen have been described) look quite alike, and most are edible, except for a few toxic ones like Agaricus xanthodermus.

However, sometimes mushrooms that not only belong to different genera but even different families can be almost indistinguishable. For example, the edible Clitopilus prunulus from the family Entolomataceae looks strikingly similar to the deadly poisonous Collybia phyllophila from the family Clitocybaceae.

Check out our article on the most dangerous look-alikes

3. Variability and Environmental Influence

In contrast and as a complement to the previous point, nature’s creations rarely resemble mass-produced items made from a single blueprint. Intraspecific variation, influenced by countless factors, can easily be misleading. In what season did the mushroom appear? Did it grow during a period of rain or through the heat of a dry season? Was it in the shade of a ravine or on the sunny edge of the forest? And what stage of development is it in — just emerging from the ground after a warm summer rain, or already starting to decay after being nibbled on by a slug? All of these factors can greatly affect the mushroom's appearance — its color, texture, shape — and if you're unaware of which key features to focus on, you might not recognize a mushroom you’ve seen before, simply because it's in a different stage of growth or grew under different conditions.

4. Insufficiency of External Features

Often, external features don't provide enough information for accurate identification. To reliably determine the species in front of you, you might need a microscope, chemical reagents, an exceptional sense of smell, a deep understanding of biotopes, extensive knowledge of the symbiotic relationships between fungi and plants, as well as familiarity with spore patterns and seasonal growth cycles. In particularly difficult cases, only a DNA analysis can give a definitive answer — but it's unlikely you have a portable molecular lab on hand (and if you did, you probably wouldn’t be reading this article).

5. Imperfect Identification Tools

Let’s say you’ve realized the complexity of the task and decided to approach mushroom identification with full seriousness. You’re not intimidated by complex terminology or thick identification guides without illustrations. You know the difference between a universal veil and a partial veil, and you’ve learned to focus on the tiniest details of hymenophore structure. The problem is that all identification tools, while helpful, remain imperfect. You might live in a place where conditions differ slightly from those where the author of your field guide worked, and the particular variety of Amanita rubescens with its unique coloration in your area doesn’t quite match the general description.

Books can contain errors, inaccuracies, or missing information. Knowledge also quickly becomes outdated — taxonomy is constantly being revised, and a mushroom you find under one name in an old book might be listed under a completely different name in an updated electronic guide. Or, for example, something once considered a single species may now be split into several distinct ones.

To put things in perspective, it was only yesterday (in historical terms) that scientists classified fungi as plants and had no idea that a porcini mushroom growing under a pine tree is, physiologically speaking, much closer to the scientists themselves than to that pine.

And then there’s subjectivity. You might read that the flesh of a mushroom darkens slowly when cut and has a faint ink-like smell, but your perception of how quickly it darkens or what ink smells like might differ significantly from that of the person who wrote the description.

Undoubtedly, apps that use artificial intelligence to identify mushrooms from photos can be a huge help, especially for beginners. But it's important to understand their limitations. Even if the neural network has been trained on a dataset of a billion high-quality photos, it can still fail if the key to accurate identification is too subtle or specific—such as spore shapes visible only under a microscope, fine distinctions in how the gills attach to the stem, or a particular smell.

Therefore, the best approach is to use all available tools, cross-check information from different sources, consult more experienced experts when needed, and, of course, gain experience over time. But always remember the possibility of serious mistakes if you become too overconfident.