I was able to get 3 Reishi Mushrooms, here's how:
Porcelain Pot
Planted sapling on Lightsday, WNG 62%
1st feeding: Ice crystal on Iceday, WXC 29%
2nd feeding: No crystal
Harvested: Darksday, WXC 7%
Planted the seed at about 1:30 am on a Saturday.
3 weeks, 3 1/2 days later on Tuesday about 5:30 pm I harvested.
Hope this is specific enough for you =)
UPDATE: 5 IS POSSIBLE!!!
Arcane Flowerpot
Tree Sapling
First Feeding: Light Crystal on Lightsday WNG71
Second Feeding: None
Harvest: Windsday WNG79
--Protey
Edited, Tue Dec 20 18:32:23 2005