Phylum: Basidiomycota. Class: Agaricomycetes. Order: Agaricales. Family: Agaricaceae
Yellow Stainers are a very important mushroom to learn to identify because of close similarities to to other local species of Agaricus mushrooms. The others are edible and delicious , Yellow Stainers are mildly toxic and taste of chemicals. They can be found in the same grassy areas as the edible species and are sometimes mixed in with them.
The general description of most Agaricus mushrooms apply to Yellow Stainers – a broad white/brown cap, a thick stem that is easy to separate cleanly from the cap and has a ring that is easily broken or removed, cuticle that can be easily peeled, crowded gills that darken with age, They also share a brownish spore print. Luckily though, there are differences.
As with all things, there is some variation between individuals. The yellowing can range from pale yellow through to a bright, chrome yellow and always turns brown after a while. If in doubt, check the base of the stem, damage there will always turn yellow. The base may even have a yellow tint when undamaged.
There are some folks who can eat Yellow Stainers without ill effects. Don’t risk it though! Poisoning will give you one to three days of diarrhea, vomiting, fever, chills, shakes, nausea, headache or any combination of those. You will generally feel lousy – I know I did! Don’t risk it, if it is yellowish and has a chemical odour, give it a miss.