Below is a walkthrough for the Give a Crystal to a Farm Dragon in Rune Factory 5. Please note that this task showed up for us on the Task Board after we completed the Find My Mommy main task.
Client: Heinz
Objective: Give a giant crystal to the farm dragon
Reward: Formula x2
After accepting the task, Heinz will give you 5 Glacies Crystal Fragments. You’ll need to take those fragments to The Crystalabra shop and trade them for a Glaceis Crystal. Bring this crystal to your farm dragon. Giving it to him will cause it to rain. Return to the Task Board to complete the task.