So the wiki says.
Stardew valley mushroom floors and infested levels.
They can also be obtained by tapping a mushroom tree.
They can also be found in the secret woods during spring and fall and on the forest farm during summer.
Mushroom floor is in 80 120.
Purple mushrooms can also be found on the forest farm map during the fall.
It does not show in 0 s or 5 s floors.
However it does not move to the next floor that floor still counts as a day so there will be no mushroom floor on the days it lands on a 5 or a 0.
If its floor 117 today it will be floor 116 the next day.
As there are 120 floors in the mine and 112 days in the stardew year you should be able to say.
One reason you are not finding the mushroom floor is because the mushroom floor has a chance to spawn zero mushrooms.
An infested floor will always be on the same level for each day and goes up one level the next day assuming that everyone starts with the same level infested can someone verify you should be able to chart out what floors are infested when.
The mushroom floor will go up 1 floor everyday if it s on floor 83 on the 3rd on the 4th it will be on floor 82.
It can be chopped down using an axe and will drop 5 6 red or purple mushrooms plus one for the stem.
A mushroom tree is a tree that spawns according to a rare event in fall.
It can also be received as a gift at the feast of the winter star.
They can be grown from wild seeds fa or in mushroom bins in the the cave if the mushroom option is chosen.
Each passing day the floor moves backwards.
This makes them farm able which is important for those looking to get two rings in particular.
You could return to the same level multiple times per day and it would always be infested and would move one level up in the mine each day you rested.
If unobstructed seeds spread by a mushroom tree have a 20 chance to grow to the next stage each day during spring.
It does not yield seeds when shaken or chopped down but it will spread seeds like a common tree.
However the mushroom floor will not appear on floors ending in a 5 or a 0.
Note that no mushrooms will spawn on an elevator floor floors ending in 0 or 5 or if the floor is infested see previous section additionally the mushroom floor is neither unique nor guaranteed there may be multiple active mushroom floors or no such floors at all on a given day and that situation may persist for several days or weeks.
Meaning one day it can be floor 90 and you won t see it.
So far i have tested this over a 5 day period when i found the infested floor on floor 68.
On year 2 summer 8th the infested level was at 53 on year 2 summer 12th the infested level was at 49 the pattern continued consistently on the.
The purple mushroom is found via foraging in the mines starting at level 81 the skull cavern from a tapped mushroom tree rarely or grown in the mushroom cave rarely.