Rare Anomalies in Mushrooms – Early Birds


reading time 2 minutes

Porcini mushrooms look like Siamese twins

© Photographer hielkje

The number of beautiful pictures of mushrooms this year is overwhelming. Some specimens stand out because they look slightly different or different. Fruit bodies with strange shapes, mirrored hats or partly conjoined as in conjoined twins (undivided twins).

The Forum also received a question about this from Mary GVK after she had photographed a strange mushroom in the Heiloöerbos: “The anomaly on the hat has the texture of a mushroom, but looks like a flower. I’ve never seen this before .” This turns out to be a form of teratology.

flower forum

Mushroom with ‘flower’

© Photographer Mary Gvk

Teratology: abnormalities in nature

The study that deals with abnormalities is called teratology and that occurs in all kinds of life forms, including mushrooms. The cause of growth abnormalities in mushrooms is often difficult to determine and can have various causes.

at the expense of

Stock fungus that is parasitic on cloud mushrooms

© Photographer tjerknawijn

Deviations can occur under the influence of insects, bacteria, viruses or parasites. For example, a cloud fungus can get crazy deformities due to the presence of a parasite fungus. In the photo above, the parasite looks pristine, unlike the cloud fungi whose remains are hard to spot.


‘Child on mother’s lap’ is a doubling of the hat in mirror image.

© Photographer tjerknawijn

If a deformity occurs at a very young stage, it may be caused by a genetic abnormality. There are indications that chemical pollution plays a role in this and affects the DNA of a young organism.

All kinds of deformities

Mushrooms can also have galls, this also falls under teratology. Among mushroom experts, the tinder fungus broadfoot fly is one of the best-known insect species. The larvae of this fly only cause galls on the tinder fungi. This tinder fungus is sometimes difficult to distinguish from the thick edged tinder fungus, unless these galls are on the tube layer.

the nipple bile

Nipple galls of the tinder fungus broadfoot fly on a flat tinder fungus

© Photographer SjanivanOphemert

There are different names for different types of teratology. These are not really different types of diseases but just another name for the same condition. For example, mushrooms with ‘fasciation’ have a doubling of the stem and ‘morellis’ has a strongly ribbed skin (just like a morel).


Young blackening puffball that consists of several deformities.

© Photographer burry

Not everything is teratology

Abnormalities in mushrooms are really rare and not every strange shape is a teratology, as in the photo below:


Cloud mushrooms (l), beech nut on mushroom (r)

© Photographer happycolor (l) and ladylove40 (r)

Links two cloud mushrooms are stacked on top of each other. The two individual mushrooms started growing in the same place at the same time. The top mushroom has been pushed up by the bottom one, but it continues to grow. This remains small because the connection with the mycelium is lost and it no longer receives nutrients and water.

To the right the solution is even simpler. The mushroom looks very special, but the bulge is simply the shell of a beech nut that has fallen on the mushroom cap. So no real teratology!

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