Link to map: https://static.wikia.nocookie.net/amongtrees_gamepedia_en/images/f/f4/Among-Trees-Map-v3-GunTech.png/revision/latest?cb=20200909123813

Its hard to spot and looks exactly like the standard morel but this had been the main area i've found any, one can even spawn in the bottom right of the area behind alot of rocks.

Outside of this particular plant, the rest are really common and can be found all around the starting area, some more uncommon ones like death cap, hedgehog, puff mushroom and porcini can be found north of the eastern bear location.