Agaricus > Agaricus arvensis

Agaricus arvensis

Agaricus arvensis
(Horse Mushroom)


These are mainly found on lawns and other grassy areas in the front range cities and plains. On wet years they can be found up into the Ponderosa pine foothills. They are a very common lawn mushroom most of the summer. Typically appearing June through August.


Agaricus arvensis stains yellow slightly on the edges where bruised or cut when fresh. It's a rather large mushroom with the cogwheel veil. It has a thin skirted ring. They can be larger than most other Agaricus species found on lawns. They are very similar to Agaricus didymus only growing in the city on lawns rather than in the woods most of the time. Both mushrooms show a cogwheel veil and look nearly identical in appearance at first. Agaricus didymus however turns more of a golden brown with age and smells more almond like. A. arvensis smells slightly almond, cherry and pleasant.

The can easily be confused with the poisonous Agaricus in section xanthodermatei however they types stain bright yellow when cut at the base of the stalk. They also tend to have a darker sunk center of the cap and longer stalk and have more of a deformed marshmallow appearance. They also smell unpleasant and phenolic more like a chalk board. They both stain yellow but in different places. A. arvensis only stains yellow on the skin edges (see pics) where A. xanthodermatei types stain in the context of the stalk, at the base. There are key differences however it can take years of observation to learn. Even experts often get it wrong. I do not suggest this mushroom for beginners for that reason. They are also often confused with A. campestris as they often grow in the same habitats. A. campestris however does not stain yellow and is somewhat smaller in size.


Colorado, Cities


Mushroomy, faint cherry

Spore Print






iNaturalist Observation

Last Updated

Jul 08 2023 08:23 PM

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