there's a harvest festival at the end of the month, and to receive certain things from franklin you need to make recipes that call for certain mushrooms. here's a link to the complete guide.
i'm just gonna keep some for the fruits basket and cornucopia as you can get harvest furniture from nooklings all month
Also, some of them might be furniture from the Mush Series (e.g. Mush TV, Mush Lamp etc.) They'll look like ordinary mushrooms until you pick it up and then you'll get a message that says something like 'Woohoo! I thought it was a mushroom, but it was actually a Forest Wall!' like I did earlier today.