Notes: Found growing in large arcs or fairy rings in grassy areas in my region, A. arvensis is commonly overlooked by the average person as being a “toadstool”.
One defining characteristic that I often use is the patchwork on the veil. Observing the underside, you will quickly notice the patches resembling a cog or gear. I enjoy collecting this mushroom as some of my friends who will not eat a chanterelle for instance will eat A. arvensis because they are already familiar with the cultivated A. bisporus.
Older collectors do not differentiate between A. arvensis & A. campestris, referring to both species as “pink bottoms”.
The common name I use the “horse mushroom”.