Edible field mushrooms, while not as common as they were when there were more small dairy farms pasturing their cattle, appear regularly in the late summer or early fall, typically after a rain when cool weather has set in. The best of these are "fairy rings" of horse mushrooms, huge relatives of the common "button" field mushrooms. The largest of the mushrooms shown in this picture was 11 inches across the top--big enough to occupy a frying pan--which it soon did.