i blanch storebought zucchini because it kills any fungus that might be on the skin, but this summer when i grew zucchini and served it right out of the garden i didn't do anything to it. the fresh zuc didn't have any fungus problems and stayed hard until the plecos finished eating it (2-3 days). store-bought can only stay in less than 24hrs before it turns to mush, even if you don't blanch it first.