May find this odd but I found this spawned in the water, on the ground and on a tree. The blues ones I found on the East side of the zone and the red ones where west. Worked for me.
This item is also a ground spawn in Innothule Swamp -- looks like a blue mushroom, whereas the swamp vegetables look like red mushrooms (both spawn alternatively in same locations). Difficult to see because they spawn underwater -- betters graphics card probably alleviates some of the problem in spotting them. Swimming also helps, although several of the spawn points are in shallow water.
Didn't note the exact spawn locations (will return when I have better data), but I noticed one spawn point near Grobb entrance, and three or four near entrance to South Ro. Will provide more info soon as my troll has a penchant for swimming, nd she loves to collect veggies for brewing.
You used to be able to mark where they were and go back to them, but now most ground spawns that I have noticed have become random. I used to add a label on the backspace map where I found them, but they no longer spawn in the marked places. One of the patches must have made them random now. The only place where I have seen ground spawns show up in the same place is with the 3 berries found in Misty Thicket down that hill on the safe side of the wall.