So, I played almost all day yesterday and I bought my sim one of those cots from Outdoor Retreat & a portable shower from that pack and off we went to the Bramblewood. We “set up camp” near the bench by Cordelia’s Secret Lot up by the top of the waterfall. Mushrooms spawn at about midnight. I have found them in this spot, almost directly across the river from this spot in a wide spot on the bank just a bit to the left of the rabbit stump there, inside the ruins, and near the snail ?. Spicy mushrooms are a winter harvestable and can sometimes be found in the garden stall, you have to check everyday though because their inventory changes a lot. I have had no luck with nightly mushrooms at all. I am not sure if they’re seasonal or not. There was a patch right at the foot of my sim’s cot but they didn’t spawn that night. It’s currently spring in my game so it may be the wrong season for those. In spring I have found verdant, lovely, and charming mushrooms so far. Mushrooms initially present themselves as strange mushrooms and have to be harvested in order to determine what variety they are, with the exception of nightly mushrooms which are labeled with what they are when you mouse over them. I tried looking in Carl’s Sims 4 Guide, but unfortunately he barely covers Cottage Living, and he doesn’t cover foraging or mushrooms at all that I can find.
Edit to add: spicy and the other special mushrooms are also included in some rewards for errands but it’s random and there’s no guarantee which variety you will get.