After the Battle of the Five Armies, after all the wounded and sick have been tended and the bodies have been discarded or buried, after reconstruction on both Dale and Erebor begin, after the snow begins to thaw to make way for the new season….
He sends for hundreds of bags from the Shire (courtesy of one Hamfast Gamgee) and, when he had the time, he’d slip away from Erebor and go out into the immense field where the battle had taken place and begins the slow process of planting the seeds.
Most of the dwarves assume that it is a strange Hobbit custom but Thorin, who watches his beloved from the battlements as he goes about planting, knows better. This gesture is something uniquely Bilbo. And more than ever does the dwarf king feel humble to even have the friendship of such a gentle heart, let alone be the keeper of it.
That spring, in the fields that had been desolated by Smaug and later covered by death and blood, flowers bloomed, covering every inch of it with white and blue blossoms.
Every inch that is, except a small space right in the middle of the field.
Though small, Thorin can still see it from the battlements.
"Why have you left that area uncovered?" He asks the hobbit.
"Well, if I covered it up with flowers where would I plant this?" Bilbo says and opens his palm to reveal the acorn he had managed to hold on to since their stay at Beorn’s.
"You told me to plant my garden when you….when you thought you would not make it," Bilbo says, barely able to contain a shudder at the memory of Thorin, bloodied and injured on the ice and ready to bid his farewell to Bilbo. "So I….I wish to plant it….here….where my new garden will grow."
Thorin looks at him in surprise, mouth parting in wonder as Bilbo looks up at him with the utmost sincerity. Then he smiles gently and brings his head down so that his and Bilbo’s foreheads touch.
"Ghivashel…you honor me."
Together they walk out into the field, to the blank space Bilbo had left untouched, and plant the acorn there, tending and caring for it as needed and watching it grow.
And many, many decades later, in the springtime, the field still bloomed without fail and a tall, proud oak tree stood amongst them.