First tree in a pot was a baby pine when I was in 6th grade, so 12ish. Then not again until a year ago at age 23.
What inspired me to begin messing with potted trees again was 2 things. one my love of gardening and being outside, but having nothing to do all winter, solution begin growing plants that grow all year(potted trees) turns out you leave most of them alone all winter anyways but whatevs. The main reason I wanted to grow miniature trees was my adolescence being spent living in rural vancouver,wa in the foothills of the cascade mountains, then at age 20 moving to Tri-Cities,wa. Tri-Cities is classified as a dessert less than 10" of precipitation per year. Nothing but sage, sand, sun, and wind in these parts. Needless to say I began to miss my trees. . . . BADLY. I am a lemur and we live in trees. So one day I was net surfing and ran across one of Kimura's forest plantings, made the decision right then and there, "I don't care how long it takes or how hard it is, I will create a mini forest/learn how to make beautiful tree art." The rest. . . all goes well. . . will be history.
My grandfather also had a good sizws potted tree collection somewhere around 25 trees. However I was very young when he had this collection and have no conscience memory of it. Who knows, maybe my toddler brain was so impressed that it stuck with me.