Growth patterns


When you find a mushroom of any kind, it's usually a good bet that it's not alone. But for many species, additional mushrooms may be spread far apart, or may mature at different times in the same area. Many of the fungi that produce large mushrooms, especially the Amanitas and Boletes, tend to have considerable space between solitary fruiting spots without any particular pattern. A pattern does exist for these genera, to a fashion, as they are mycorrhizal and must fruit within proximity to their host's root system.


Many of the saprotrophic fungi are known to grow in clusters. The definition of a cluster is where many mushrooms grow from a single point of origin.

Clustered growth can be a major diagnostic character for many fungi. Some of the most well known clustering mushrooms are Gymnopilus and Naematoloma (likely the genus in the photo).


Saying that mushrooms are found in troops is basically saying that many individual fruitings can be found in a relatively small area.

Troops can be formed from gregarious fruitings of a single fungus within a single food source, such as these Stropharia mushrooms in a log (top photo).

Or, it could be many independant fruitings within a heavily colonized substrate such as these hundreds of Marasmius scattered across the forest humus (bottom photo).

There is a large array of fungi that tend to produce many, many small mushrooms in a small space. Often these mushrooms earn the name LBM (Little Brown Mushrooms), and because of their size and ubiquity, are very difficult to identify. Most foragers don't even bother. But for those who call themselves amateur mycologists, these fruitings can be both attractive and a fun taxonomic challenge.

There certainly are fungi that produce larger mushrooms in troops. Some very large mushrooms can be found in great abundance when conditions are right. It is important to understand, however, that when a field guide says that a particular species appears in troops, that it is a characterization of the typical fruiting pattern. An unusually wet year may bring about an abundance of mushrooms, but those species that are characterized by their fruiting in troops will typically do so whenever they appear.


"Fairy rings" are very fun to come across, and there are some common urban mushrooms that consistently appear in this interesting pattern.

Mushrooms can appear in a ring pattern for two possible reasons:

1. The underground fungal colony began as a single spore and is radiating out uniformly from the point of origin. This pattern of mycelial expansion can be the bane of golf courses, as it tends to produce rings of fast growing grass as nutrients are liberated by the decomposition of grass clippings.

In parts of the country that get decent rainfall, a common ring producing mushroom is Marasmius oreades, "The Fairy Ring Mushroom". M. oreades is a great edible and is highly prized in Mexico and among foragers who are familiar with it.

But, before you get all excited about the fairy ring you saw in the park, there is another common ring-forming mushroom that causes terrible stomach upset. Chlorophyllum molybdites, the green gilled parasol mushroom, is common in the Southwest and is the most common source of mushroom poisoning in the region.

2. The mushrooms are produced by mycorrhizal fungi, and the ring represents the outer tips of the host root system. This is less common, and most mycorrhizal fungi do not produce rings. You are most likely to observe such a pattern if the host(s) are young and their root systems are restricted and uniform.

Photo: JEFF SCHRIER / The Saginaw News