From an edifying friar:
"I turned to study the Church fathers because, when I was a young friar, St. Francis started to give me indigestion. Not St. Francis himself, but the way they used him. Without an idea of the tradition of religious life they would justify any crazy thing they wanted to do with, 'St. Francis says this...' or 'St. Francis says we have to...' as if St. Francis was born like a mushroom."
Apparently, to be born like a mushroom is a French saying that suggests someone or something born ex nihilo, without provenance or parentage.