Grian who's probably been sheltered his entire life, all he knows is his kingdom walls vs Scar who hasn't stayed inside a day in his life despite his family's best attempts to make him act like a proper prince and heir to the throne.
Grian, who's first impression of Scar is when he's first set to meet his arranged fiancé before his marriage, and ends up finding him knee deep in muddy garden helping plant flowers for the coming season. Grian who first assumes scar is some gardener only to get caught off guard when an actual guard scold scar and calls him 'prince'
AGhghsg beats you up.
Grian literally has no idea what to think of Scar. Scar behaves so differently and has such a different upbringing from him. Grian thrives in the safety of the kingdom, that's all he knows, he's been taught he should only feel safe amongst the kingdom walls. And Scar seems to want the opposite, he wants out, and maybe he doesn't understand why Grian doesn't want that.
I'd say the garden is a middle ground for both of them. A place that still feels safe to Grian while still offers something new and interesting to Scar. He loves planting flowers, even if he's constantly scolded for getting his pristine clothes dirty. And Grian likes to sit with him, watch his rougher hands work, not afraid to dig into the dirt and find the best places for so many flowers.
Grian has an interest in plants, although most of his knowledge is simply from books and never discussed the actual care of these plants. Scar seems to know the names of every plant, how to plant them, when to plant them for optimal growth, and he likes to chat while he's working too.
It sets a good base for their marriage, lets them get closer and understand why they each feel the way they do, why Grian wants to stay caged, and why Scar wants to escape.