After looking through some field guides today, I was surprised to learn that this “little brown mushroom” (or LBM for short) is very common. (“How’s that”, I thought. “I can’t remember ever noticing it before!”) But notice it I did on this cool November afternoon— when countless colonies of LBM’s were coming up in my neighbor’s lawn after a rain. Appearing crisp and fresh, I couldn’t help but drop to the ground to get a better look at this miniature world. The soft brown caps contrasting with white, lanky stems intrigued me.
Haymaker’s Mushroom (or Lawnmower’s Mushroom) is a hygrophanous* species with a bell-shaped, brown cap when it is new. As the cap begins to dry out, the color fades to tan, leaving patches or concentric circles of lighter color behind. Little lines, or striations, are usually present around the edge of the cap. The gills also change color with time— from pale gray on a new mushroom to dark brown later.
The stem (1 to 3 inches long) is narrow, and about the same thickness from top to bottom. It is hollow, fragile, and lined with vertical ridges. Eventually the cap flattens to a diameter of about 1 inch. A spore print will be dark brown to black.
This mushroom feeds on decaying organic matter. It is often found in recently mowed grassy habitats after a rain, hence the two common names. This LBM is not edible and may in fact be poisonous.
Note: *When mushrooms change color over time as the result of losing or gaining water, they are called “hygrophanous”.
(Don’t be confused by the wood in the background of these shots. The mushrooms were coming up in the grass and weeds next to a pile of firewood.)