Morel has a request that involves Swinub's ability to detect mushrooms.
The Request
After you complete What a Massive Mushroom!, check on the blackboard in Professor Laventon's office in Galaxy Hall in Jubilife Village to accept this request.
Talk to Morel
Go to the Alabaster Icelands and talk to Morel near Heart's Crag.
Search for Mushrooms with Swinub
Add a Swinub to your party and go to the guidance markers in the Heart's Crag area. At one of them, a Snover will attack. Catch or defeat it.
Reward
After you have investigated all three locations with Swinub, go back and talk to Morel to get 5 Sand Radish and 1 Exp. Candy L.