It’s a question many home and food service cooks deal with: what’s up with mushrooms? Should they be washed, what with that crud on them, and does washing turn fresh mushrooms into mush?

I cook mushrooms.

Kathie T. Hodge, an associate professor of mycology at Cornell who writes the Cornell Mushroom Blog told the N.Y Times, “Even if you don’t clean the mushrooms, it’s probably fine.”

Common grocery store mushrooms, Agaricus bisporus, which include the white button, cremini and portobello varieties, “are grown in what is basically compost,” she said. “It’s usually heat-treated, not entirely sterile, but a lot of organisms have been killed.”

Every producer has its own recipe, including organic things like straw, peat moss, manure if it is obtainable, canola meal or cottonseed meal, and inorganic things like lime or gypsum. Then it is allowed to compost — that is, ferment — and then it is heat-treated, “trying to get rid of most things so the mushrooms will take over,” Dr. Hodge said.