STORY OF SEASONS: Pioneers of Olive Town

You will first need to repair the rotted log in the second area of your farmland if you're wanting to harvest mushrooms. These are nice little money attachments to any other shipments that are going out that day, and some recipes in Cooking will require some of the six varieties you have access to grow. Now, despite the haul of mushrooms you get per log, it only counts when you interact with the log to pull the crop off, so you will need to either interact with fifty fully-mature mushroom crops, or buy more logs after repairing the first to increase productivity.

1) Repair the log. This is found in Area 2 and will require Solid Log x20, Clay x30, Flexible Grass x40. Once this is repaired, you will unlock the Cultivating skill and the ability to ship mushrooms off to get spores to appear in the General Store.
2) Plant spores to grow mushrooms.
3) Wait 4 days.
4) Harvest for profit or cooking.
5) Rinse and repeat steps 2 through 4 as you see fit, or to level the skill.