Below is a walkthrough for the Harvest a Potato task in Rune Factory 5.
Client: Lucy
Objective: Harvest a potato from your farm
Reward(s): New Shop Inventory (Raddis Seeds)
After accepting this task from the Task Board, Lucy will show up and challenge you to harvest a potato. If you don’t have any Potato Seeds, you should be able to buy them from the General Store for 80G each. When you have the seeds, plant some at your farm and make sure to water them every day. It takes 7 days for the potatoes to be harvestable. Once you harvest your first one, return to the Task Board to complete the request.