When: 2007-09-05

Collection location: Prior Lake, Minnesota, USA [Click for map]

Who: rpeters

No specimen available

This is a very deceptive mushroom. It looks identicle to Agaricus campestris, the common (and edible) meadow mushroom. But, this one is NOT edible. To distinguish it from campestris, but a drop of KOH (Potassium Hydroxide) solution on the cap or stem. If it turns yellow, it is A. californicus. Another indicator is where it is growing. A. campestris growns in fields, as its name implies. A. californicus growns in woods. This sample was found under White Pine and near Oak in a mixed forest, not more than 10’ from a field. The KOH reaction is very rapid with a fresh sample, but may take a few minutes with an older mushroom. The photographs show mature specimens. The spore print is also identicle to A. campestris, a deep chocolate brown. What this mushroom is doing in Minnesota is a mystery to me as it is, by its name, a west-coast species. I have found this mushroom several times this year in many different locations, never in years past. It is a shame that it is somewhat poisonous as they are nice large mushrooms. The second photo shows the KOH reaction on the cap and stem.


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Thanks for the notes!
By: Nathan Wilson (nathan)
2007-09-05 10:42:57 PDT (-0700)

It’s great to get some notes written on the species as well as notes related to the specific observation. Just so you know, the intention for the site is that species notes should go on the ‘Name Page’ for the species and just the notes relevant to a specific observation should go with that observation. I took the liberty of copying your observation notes into http://mushroomobserver.org/observer/show_name/397">A. californicus. One of the advantages of putting the species related notes on the name page is that others can review them, fix typos and add additional information. The name page for a species is always available from an observation page by clicking the ’About ’ link at near the top of the page.